* [Qemu-devel] [PATCH v5 01/11] raw-posix: add raw_get_aio_fd() for virtio-blk-data-plane
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
@ 2012-12-05 20:47 ` Stefan Hajnoczi
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 02/11] configure: add CONFIG_VIRTIO_BLK_DATA_PLANE Stefan Hajnoczi
` (11 subsequent siblings)
12 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-05 20:47 UTC (permalink / raw)
To: qemu-devel
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
The raw_get_aio_fd() function allows virtio-blk-data-plane to get the
file descriptor of a raw image file with Linux AIO enabled. This
interface is really a layering violation that can be resolved once the
block layer is able to run outside the global mutex - at that point
virtio-blk-data-plane will switch from custom Linux AIO code to using
the block layer.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
block.h | 9 +++++++++
block/raw-posix.c | 34 ++++++++++++++++++++++++++++++++++
2 files changed, 43 insertions(+)
diff --git a/block.h b/block.h
index 722c620..2dc6aaf 100644
--- a/block.h
+++ b/block.h
@@ -365,6 +365,15 @@ void bdrv_disable_copy_on_read(BlockDriverState *bs);
void bdrv_set_in_use(BlockDriverState *bs, int in_use);
int bdrv_in_use(BlockDriverState *bs);
+#ifdef CONFIG_LINUX_AIO
+int raw_get_aio_fd(BlockDriverState *bs);
+#else
+static inline int raw_get_aio_fd(BlockDriverState *bs)
+{
+ return -ENOTSUP;
+}
+#endif
+
enum BlockAcctType {
BDRV_ACCT_READ,
BDRV_ACCT_WRITE,
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 550c81f..16cff9b 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -1784,6 +1784,40 @@ static BlockDriver bdrv_host_cdrom = {
};
#endif /* __FreeBSD__ */
+#ifdef CONFIG_LINUX_AIO
+/**
+ * Return the file descriptor for Linux AIO
+ *
+ * This function is a layering violation and should be removed when it becomes
+ * possible to call the block layer outside the global mutex. It allows the
+ * caller to hijack the file descriptor so I/O can be performed outside the
+ * block layer.
+ */
+int raw_get_aio_fd(BlockDriverState *bs)
+{
+ BDRVRawState *s;
+
+ if (!bs->drv) {
+ return -ENOMEDIUM;
+ }
+
+ if (bs->drv == bdrv_find_format("raw")) {
+ bs = bs->file;
+ }
+
+ /* raw-posix has several protocols so just check for raw_aio_readv */
+ if (bs->drv->bdrv_aio_readv != raw_aio_readv) {
+ return -ENOTSUP;
+ }
+
+ s = bs->opaque;
+ if (!s->use_aio) {
+ return -ENOTSUP;
+ }
+ return s->fd;
+}
+#endif /* CONFIG_LINUX_AIO */
+
static void bdrv_file_init(void)
{
/*
--
1.8.0.1
^ permalink raw reply related [flat|nested] 34+ messages in thread* [Qemu-devel] [PATCH v5 02/11] configure: add CONFIG_VIRTIO_BLK_DATA_PLANE
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 01/11] raw-posix: add raw_get_aio_fd() for virtio-blk-data-plane Stefan Hajnoczi
@ 2012-12-05 20:47 ` Stefan Hajnoczi
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 03/11] dataplane: add host memory mapping code Stefan Hajnoczi
` (10 subsequent siblings)
12 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-05 20:47 UTC (permalink / raw)
To: qemu-devel
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
The virtio-blk-data-plane feature only works with Linux AIO. Therefore
add a ./configure option and necessary checks to implement this
dependency.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
configure | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/configure b/configure
index 994f731..026a6c1 100755
--- a/configure
+++ b/configure
@@ -223,6 +223,7 @@ libiscsi=""
coroutine=""
seccomp=""
glusterfs=""
+virtio_blk_data_plane=""
# parse CC options first
for opt do
@@ -871,6 +872,10 @@ for opt do
;;
--enable-glusterfs) glusterfs="yes"
;;
+ --disable-virtio-blk-data-plane) virtio_blk_data_plane="no"
+ ;;
+ --enable-virtio-blk-data-plane) virtio_blk_data_plane="yes"
+ ;;
*) echo "ERROR: unknown option $opt"; show_help="yes"
;;
esac
@@ -2248,6 +2253,17 @@ EOF
fi
##########################################
+# adjust virtio-blk-data-plane based on linux-aio
+
+if test "$virtio_blk_data_plane" = "yes" -a \
+ "$linux_aio" != "yes" ; then
+ echo "Error: virtio-blk-data-plane requires Linux AIO, please try --enable-linux-aio"
+ exit 1
+elif test -z "$virtio_blk_data_plane" ; then
+ virtio_blk_data_plane=$linux_aio
+fi
+
+##########################################
# attr probe
if test "$attr" != "no" ; then
@@ -3250,6 +3266,7 @@ echo "build guest agent $guest_agent"
echo "seccomp support $seccomp"
echo "coroutine backend $coroutine_backend"
echo "GlusterFS support $glusterfs"
+echo "virtio-blk-data-plane $virtio_blk_data_plane"
if test "$sdl_too_old" = "yes"; then
echo "-> Your SDL version is too old - please upgrade to have SDL support"
@@ -3596,6 +3613,10 @@ if test "$glusterfs" = "yes" ; then
echo "CONFIG_GLUSTERFS=y" >> $config_host_mak
fi
+if test "$virtio_blk_data_plane" = "yes" ; then
+ echo "CONFIG_VIRTIO_BLK_DATA_PLANE=y" >> $config_host_mak
+fi
+
# USB host support
case "$usb" in
linux)
--
1.8.0.1
^ permalink raw reply related [flat|nested] 34+ messages in thread* [Qemu-devel] [PATCH v5 03/11] dataplane: add host memory mapping code
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 01/11] raw-posix: add raw_get_aio_fd() for virtio-blk-data-plane Stefan Hajnoczi
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 02/11] configure: add CONFIG_VIRTIO_BLK_DATA_PLANE Stefan Hajnoczi
@ 2012-12-05 20:47 ` Stefan Hajnoczi
2012-12-09 4:02 ` liu ping fan
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 04/11] dataplane: add virtqueue vring code Stefan Hajnoczi
` (9 subsequent siblings)
12 siblings, 1 reply; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-05 20:47 UTC (permalink / raw)
To: qemu-devel
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
The data plane thread needs to map guest physical addresses to host
pointers. Normally this is done with cpu_physical_memory_map() but the
function assumes the global mutex is held. The data plane thread does
not touch the global mutex and therefore needs a thread-safe memory
mapping mechanism.
Hostmem registers a MemoryListener similar to how vhost collects and
pushes memory region information into the kernel. There is a
fine-grained lock on the regions list which is held during lookup and
when installing a new regions list.
When the physical memory map changes the MemoryListener callbacks are
invoked. They build up a new list of memory regions which is finally
installed when the list has been completed.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/dataplane/Makefile.objs | 3 +
hw/dataplane/hostmem.c | 173 +++++++++++++++++++++++++++++++++++++++++++++
hw/dataplane/hostmem.h | 57 +++++++++++++++
3 files changed, 233 insertions(+)
create mode 100644 hw/dataplane/Makefile.objs
create mode 100644 hw/dataplane/hostmem.c
create mode 100644 hw/dataplane/hostmem.h
diff --git a/hw/dataplane/Makefile.objs b/hw/dataplane/Makefile.objs
new file mode 100644
index 0000000..8c8dea1
--- /dev/null
+++ b/hw/dataplane/Makefile.objs
@@ -0,0 +1,3 @@
+ifeq ($(CONFIG_VIRTIO), y)
+common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o
+endif
diff --git a/hw/dataplane/hostmem.c b/hw/dataplane/hostmem.c
new file mode 100644
index 0000000..ae92ca2
--- /dev/null
+++ b/hw/dataplane/hostmem.c
@@ -0,0 +1,173 @@
+/*
+ * Thread-safe guest to host memory mapping
+ *
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "exec-memory.h"
+#include "hostmem.h"
+
+static int hostmem_lookup_cmp(const void *phys_, const void *region_)
+{
+ hwaddr phys = *(const hwaddr *)phys_;
+ const HostmemRegion *region = region_;
+
+ if (phys < region->guest_addr) {
+ return -1;
+ } else if (phys >= region->guest_addr + region->size) {
+ return 1;
+ } else {
+ return 0;
+ }
+}
+
+/**
+ * Map guest physical address to host pointer
+ */
+void *hostmem_lookup(Hostmem *hostmem, hwaddr phys, hwaddr len, bool is_write)
+{
+ HostmemRegion *region;
+ void *host_addr = NULL;
+ hwaddr offset_within_region;
+
+ qemu_mutex_lock(&hostmem->current_regions_lock);
+ region = bsearch(&phys, hostmem->current_regions,
+ hostmem->num_current_regions,
+ sizeof(hostmem->current_regions[0]),
+ hostmem_lookup_cmp);
+ if (!region) {
+ goto out;
+ }
+ if (is_write && region->readonly) {
+ goto out;
+ }
+ offset_within_region = phys - region->guest_addr;
+ if (offset_within_region + len <= region->size) {
+ host_addr = region->host_addr + offset_within_region;
+ }
+out:
+ qemu_mutex_unlock(&hostmem->current_regions_lock);
+
+ return host_addr;
+}
+
+/**
+ * Install new regions list
+ */
+static void hostmem_listener_commit(MemoryListener *listener)
+{
+ Hostmem *hostmem = container_of(listener, Hostmem, listener);
+
+ qemu_mutex_lock(&hostmem->current_regions_lock);
+ g_free(hostmem->current_regions);
+ hostmem->current_regions = hostmem->new_regions;
+ hostmem->num_current_regions = hostmem->num_new_regions;
+ qemu_mutex_unlock(&hostmem->current_regions_lock);
+
+ /* Reset new regions list */
+ hostmem->new_regions = NULL;
+ hostmem->num_new_regions = 0;
+}
+
+/**
+ * Add a MemoryRegionSection to the new regions list
+ */
+static void hostmem_append_new_region(Hostmem *hostmem,
+ MemoryRegionSection *section)
+{
+ void *ram_ptr = memory_region_get_ram_ptr(section->mr);
+ size_t num = hostmem->num_new_regions;
+ size_t new_size = (num + 1) * sizeof(hostmem->new_regions[0]);
+
+ hostmem->new_regions = g_realloc(hostmem->new_regions, new_size);
+ hostmem->new_regions[num] = (HostmemRegion){
+ .host_addr = ram_ptr + section->offset_within_region,
+ .guest_addr = section->offset_within_address_space,
+ .size = section->size,
+ .readonly = section->readonly,
+ };
+ hostmem->num_new_regions++;
+}
+
+static void hostmem_listener_append_region(MemoryListener *listener,
+ MemoryRegionSection *section)
+{
+ Hostmem *hostmem = container_of(listener, Hostmem, listener);
+
+ /* Ignore non-RAM regions, we may not be able to map them */
+ if (!memory_region_is_ram(section->mr)) {
+ return;
+ }
+
+ /* Ignore regions with dirty logging, we cannot mark them dirty */
+ if (memory_region_is_logging(section->mr)) {
+ return;
+ }
+
+ hostmem_append_new_region(hostmem, section);
+}
+
+/* We don't implement most MemoryListener callbacks, use these nop stubs */
+static void hostmem_listener_dummy(MemoryListener *listener)
+{
+}
+
+static void hostmem_listener_section_dummy(MemoryListener *listener,
+ MemoryRegionSection *section)
+{
+}
+
+static void hostmem_listener_eventfd_dummy(MemoryListener *listener,
+ MemoryRegionSection *section,
+ bool match_data, uint64_t data,
+ EventNotifier *e)
+{
+}
+
+static void hostmem_listener_coalesced_mmio_dummy(MemoryListener *listener,
+ MemoryRegionSection *section,
+ hwaddr addr, hwaddr len)
+{
+}
+
+void hostmem_init(Hostmem *hostmem)
+{
+ memset(hostmem, 0, sizeof(*hostmem));
+
+ hostmem->listener = (MemoryListener){
+ .begin = hostmem_listener_dummy,
+ .commit = hostmem_listener_commit,
+ .region_add = hostmem_listener_append_region,
+ .region_del = hostmem_listener_section_dummy,
+ .region_nop = hostmem_listener_append_region,
+ .log_start = hostmem_listener_section_dummy,
+ .log_stop = hostmem_listener_section_dummy,
+ .log_sync = hostmem_listener_section_dummy,
+ .log_global_start = hostmem_listener_dummy,
+ .log_global_stop = hostmem_listener_dummy,
+ .eventfd_add = hostmem_listener_eventfd_dummy,
+ .eventfd_del = hostmem_listener_eventfd_dummy,
+ .coalesced_mmio_add = hostmem_listener_coalesced_mmio_dummy,
+ .coalesced_mmio_del = hostmem_listener_coalesced_mmio_dummy,
+ .priority = 10,
+ };
+
+ memory_listener_register(&hostmem->listener, &address_space_memory);
+ if (hostmem->num_new_regions > 0) {
+ hostmem_listener_commit(&hostmem->listener);
+ }
+}
+
+void hostmem_finalize(Hostmem *hostmem)
+{
+ memory_listener_unregister(&hostmem->listener);
+ g_free(hostmem->new_regions);
+ g_free(hostmem->current_regions);
+}
diff --git a/hw/dataplane/hostmem.h b/hw/dataplane/hostmem.h
new file mode 100644
index 0000000..6d87841
--- /dev/null
+++ b/hw/dataplane/hostmem.h
@@ -0,0 +1,57 @@
+/*
+ * Thread-safe guest to host memory mapping
+ *
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef HOSTMEM_H
+#define HOSTMEM_H
+
+#include "memory.h"
+#include "qemu-thread.h"
+
+typedef struct {
+ void *host_addr;
+ hwaddr guest_addr;
+ uint64_t size;
+ bool readonly;
+} HostmemRegion;
+
+typedef struct {
+ /* The listener is invoked when regions change and a new list of regions is
+ * built up completely before they are installed.
+ */
+ MemoryListener listener;
+ HostmemRegion *new_regions;
+ size_t num_new_regions;
+
+ /* Current regions are accessed from multiple threads either to lookup
+ * addresses or to install a new list of regions. The lock protects the
+ * pointer and the regions.
+ */
+ QemuMutex current_regions_lock;
+ HostmemRegion *current_regions;
+ size_t num_current_regions;
+} Hostmem;
+
+void hostmem_init(Hostmem *hostmem);
+void hostmem_finalize(Hostmem *hostmem);
+
+/**
+ * Map a guest physical address to a pointer
+ *
+ * Note that there is map/unmap mechanism here. The caller must ensure that
+ * mapped memory is no longer used across events like hot memory unplug. This
+ * can be done with other mechanisms like bdrv_drain_all() that quiesce
+ * in-flight I/O.
+ */
+void *hostmem_lookup(Hostmem *hostmem, hwaddr phys, hwaddr len, bool is_write);
+
+#endif /* HOSTMEM_H */
--
1.8.0.1
^ permalink raw reply related [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 03/11] dataplane: add host memory mapping code
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 03/11] dataplane: add host memory mapping code Stefan Hajnoczi
@ 2012-12-09 4:02 ` liu ping fan
2012-12-09 10:36 ` Stefan Hajnoczi
0 siblings, 1 reply; 34+ messages in thread
From: liu ping fan @ 2012-12-09 4:02 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, qemu-devel,
Blue Swirl, khoa, Paolo Bonzini, asias
On Thu, Dec 6, 2012 at 4:47 AM, Stefan Hajnoczi <stefanha@redhat.com> wrote:
> The data plane thread needs to map guest physical addresses to host
> pointers. Normally this is done with cpu_physical_memory_map() but the
> function assumes the global mutex is held. The data plane thread does
> not touch the global mutex and therefore needs a thread-safe memory
> mapping mechanism.
>
> Hostmem registers a MemoryListener similar to how vhost collects and
> pushes memory region information into the kernel. There is a
> fine-grained lock on the regions list which is held during lookup and
> when installing a new regions list.
>
> When the physical memory map changes the MemoryListener callbacks are
> invoked. They build up a new list of memory regions which is finally
> installed when the list has been completed.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> hw/dataplane/Makefile.objs | 3 +
> hw/dataplane/hostmem.c | 173 +++++++++++++++++++++++++++++++++++++++++++++
> hw/dataplane/hostmem.h | 57 +++++++++++++++
> 3 files changed, 233 insertions(+)
> create mode 100644 hw/dataplane/Makefile.objs
> create mode 100644 hw/dataplane/hostmem.c
> create mode 100644 hw/dataplane/hostmem.h
>
> diff --git a/hw/dataplane/Makefile.objs b/hw/dataplane/Makefile.objs
> new file mode 100644
> index 0000000..8c8dea1
> --- /dev/null
> +++ b/hw/dataplane/Makefile.objs
> @@ -0,0 +1,3 @@
> +ifeq ($(CONFIG_VIRTIO), y)
> +common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o
> +endif
> diff --git a/hw/dataplane/hostmem.c b/hw/dataplane/hostmem.c
> new file mode 100644
> index 0000000..ae92ca2
> --- /dev/null
> +++ b/hw/dataplane/hostmem.c
> @@ -0,0 +1,173 @@
> +/*
> + * Thread-safe guest to host memory mapping
> + *
> + * Copyright 2012 Red Hat, Inc. and/or its affiliates
> + *
> + * Authors:
> + * Stefan Hajnoczi <stefanha@redhat.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include "exec-memory.h"
> +#include "hostmem.h"
> +
> +static int hostmem_lookup_cmp(const void *phys_, const void *region_)
> +{
> + hwaddr phys = *(const hwaddr *)phys_;
> + const HostmemRegion *region = region_;
> +
> + if (phys < region->guest_addr) {
> + return -1;
> + } else if (phys >= region->guest_addr + region->size) {
> + return 1;
> + } else {
> + return 0;
> + }
> +}
> +
> +/**
> + * Map guest physical address to host pointer
> + */
> +void *hostmem_lookup(Hostmem *hostmem, hwaddr phys, hwaddr len, bool is_write)
> +{
> + HostmemRegion *region;
> + void *host_addr = NULL;
> + hwaddr offset_within_region;
> +
> + qemu_mutex_lock(&hostmem->current_regions_lock);
> + region = bsearch(&phys, hostmem->current_regions,
> + hostmem->num_current_regions,
> + sizeof(hostmem->current_regions[0]),
> + hostmem_lookup_cmp);
> + if (!region) {
> + goto out;
> + }
> + if (is_write && region->readonly) {
> + goto out;
> + }
> + offset_within_region = phys - region->guest_addr;
> + if (offset_within_region + len <= region->size) {
> + host_addr = region->host_addr + offset_within_region;
> + }
> +out:
> + qemu_mutex_unlock(&hostmem->current_regions_lock);
> +
> + return host_addr;
> +}
> +
> +/**
> + * Install new regions list
> + */
> +static void hostmem_listener_commit(MemoryListener *listener)
> +{
> + Hostmem *hostmem = container_of(listener, Hostmem, listener);
> +
> + qemu_mutex_lock(&hostmem->current_regions_lock);
> + g_free(hostmem->current_regions);
> + hostmem->current_regions = hostmem->new_regions;
> + hostmem->num_current_regions = hostmem->num_new_regions;
> + qemu_mutex_unlock(&hostmem->current_regions_lock);
> +
> + /* Reset new regions list */
> + hostmem->new_regions = NULL;
> + hostmem->num_new_regions = 0;
> +}
> +
> +/**
> + * Add a MemoryRegionSection to the new regions list
> + */
> +static void hostmem_append_new_region(Hostmem *hostmem,
> + MemoryRegionSection *section)
> +{
> + void *ram_ptr = memory_region_get_ram_ptr(section->mr);
> + size_t num = hostmem->num_new_regions;
> + size_t new_size = (num + 1) * sizeof(hostmem->new_regions[0]);
> +
> + hostmem->new_regions = g_realloc(hostmem->new_regions, new_size);
> + hostmem->new_regions[num] = (HostmemRegion){
> + .host_addr = ram_ptr + section->offset_within_region,
> + .guest_addr = section->offset_within_address_space,
> + .size = section->size,
> + .readonly = section->readonly,
> + };
> + hostmem->num_new_regions++;
> +}
> +
> +static void hostmem_listener_append_region(MemoryListener *listener,
> + MemoryRegionSection *section)
> +{
> + Hostmem *hostmem = container_of(listener, Hostmem, listener);
> +
> + /* Ignore non-RAM regions, we may not be able to map them */
> + if (!memory_region_is_ram(section->mr)) {
> + return;
> + }
> +
> + /* Ignore regions with dirty logging, we cannot mark them dirty */
> + if (memory_region_is_logging(section->mr)) {
> + return;
> + }
> +
> + hostmem_append_new_region(hostmem, section);
> +}
> +
> +/* We don't implement most MemoryListener callbacks, use these nop stubs */
> +static void hostmem_listener_dummy(MemoryListener *listener)
> +{
> +}
> +
> +static void hostmem_listener_section_dummy(MemoryListener *listener,
> + MemoryRegionSection *section)
> +{
> +}
> +
> +static void hostmem_listener_eventfd_dummy(MemoryListener *listener,
> + MemoryRegionSection *section,
> + bool match_data, uint64_t data,
> + EventNotifier *e)
> +{
> +}
> +
> +static void hostmem_listener_coalesced_mmio_dummy(MemoryListener *listener,
> + MemoryRegionSection *section,
> + hwaddr addr, hwaddr len)
> +{
> +}
> +
> +void hostmem_init(Hostmem *hostmem)
> +{
> + memset(hostmem, 0, sizeof(*hostmem));
> +
> + hostmem->listener = (MemoryListener){
> + .begin = hostmem_listener_dummy,
> + .commit = hostmem_listener_commit,
I think, here, if we sync on big lock, and flush out dangling pointer
in data-plane thread, then we can survive from the unplug.
> + .region_add = hostmem_listener_append_region,
> + .region_del = hostmem_listener_section_dummy,
And here we should remove the corresponding info in hostmem
Regards,
Pingfan
> + .region_nop = hostmem_listener_append_region,
> + .log_start = hostmem_listener_section_dummy,
> + .log_stop = hostmem_listener_section_dummy,
> + .log_sync = hostmem_listener_section_dummy,
> + .log_global_start = hostmem_listener_dummy,
> + .log_global_stop = hostmem_listener_dummy,
> + .eventfd_add = hostmem_listener_eventfd_dummy,
> + .eventfd_del = hostmem_listener_eventfd_dummy,
> + .coalesced_mmio_add = hostmem_listener_coalesced_mmio_dummy,
> + .coalesced_mmio_del = hostmem_listener_coalesced_mmio_dummy,
> + .priority = 10,
> + };
> +
> + memory_listener_register(&hostmem->listener, &address_space_memory);
> + if (hostmem->num_new_regions > 0) {
> + hostmem_listener_commit(&hostmem->listener);
> + }
> +}
> +
> +void hostmem_finalize(Hostmem *hostmem)
> +{
> + memory_listener_unregister(&hostmem->listener);
> + g_free(hostmem->new_regions);
> + g_free(hostmem->current_regions);
> +}
> diff --git a/hw/dataplane/hostmem.h b/hw/dataplane/hostmem.h
> new file mode 100644
> index 0000000..6d87841
> --- /dev/null
> +++ b/hw/dataplane/hostmem.h
> @@ -0,0 +1,57 @@
> +/*
> + * Thread-safe guest to host memory mapping
> + *
> + * Copyright 2012 Red Hat, Inc. and/or its affiliates
> + *
> + * Authors:
> + * Stefan Hajnoczi <stefanha@redhat.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#ifndef HOSTMEM_H
> +#define HOSTMEM_H
> +
> +#include "memory.h"
> +#include "qemu-thread.h"
> +
> +typedef struct {
> + void *host_addr;
> + hwaddr guest_addr;
> + uint64_t size;
> + bool readonly;
> +} HostmemRegion;
> +
> +typedef struct {
> + /* The listener is invoked when regions change and a new list of regions is
> + * built up completely before they are installed.
> + */
> + MemoryListener listener;
> + HostmemRegion *new_regions;
> + size_t num_new_regions;
> +
> + /* Current regions are accessed from multiple threads either to lookup
> + * addresses or to install a new list of regions. The lock protects the
> + * pointer and the regions.
> + */
> + QemuMutex current_regions_lock;
> + HostmemRegion *current_regions;
> + size_t num_current_regions;
> +} Hostmem;
> +
> +void hostmem_init(Hostmem *hostmem);
> +void hostmem_finalize(Hostmem *hostmem);
> +
> +/**
> + * Map a guest physical address to a pointer
> + *
> + * Note that there is map/unmap mechanism here. The caller must ensure that
> + * mapped memory is no longer used across events like hot memory unplug. This
> + * can be done with other mechanisms like bdrv_drain_all() that quiesce
> + * in-flight I/O.
> + */
> +void *hostmem_lookup(Hostmem *hostmem, hwaddr phys, hwaddr len, bool is_write);
> +
> +#endif /* HOSTMEM_H */
> --
> 1.8.0.1
>
>
^ permalink raw reply [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 03/11] dataplane: add host memory mapping code
2012-12-09 4:02 ` liu ping fan
@ 2012-12-09 10:36 ` Stefan Hajnoczi
0 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-09 10:36 UTC (permalink / raw)
To: liu ping fan
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, qemu-devel,
Blue Swirl, khoa, Paolo Bonzini, asias
On Sun, Dec 09, 2012 at 12:02:52PM +0800, liu ping fan wrote:
> On Thu, Dec 6, 2012 at 4:47 AM, Stefan Hajnoczi <stefanha@redhat.com> wrote:
> > +void hostmem_init(Hostmem *hostmem)
> > +{
> > + memset(hostmem, 0, sizeof(*hostmem));
> > +
> > + hostmem->listener = (MemoryListener){
> > + .begin = hostmem_listener_dummy,
> > + .commit = hostmem_listener_commit,
>
> I think, here, if we sync on big lock, and flush out dangling pointer
> in data-plane thread, then we can survive from the unplug.
Hot unplug support requires that the data plane thread completes all
requests and doesn't process any new requests until the critical region
completes (e.g. hot memory unplug).
vm_stop() + bdrv_drain_all() achieves this:
1. vcpus are stopped so no new requests can be submitted by the guest.
2. bdrv_drain_all() completes all Linux AIO requests so we're no longer
accessing guest memory.
vcpus should be enabled again after hot unplug.
> > + .region_add = hostmem_listener_append_region,
> > + .region_del = hostmem_listener_section_dummy,
>
> And here we should remove the corresponding info in hostmem
.region_del() is not necessary because we rebuild a fresh memory region
list. We never update the memory region list once it has been
installed.
This means the .region_add() and .region_nop() information is enough to
build a fresh list from scratch.
Stefan
^ permalink raw reply [flat|nested] 34+ messages in thread
* [Qemu-devel] [PATCH v5 04/11] dataplane: add virtqueue vring code
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
` (2 preceding siblings ...)
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 03/11] dataplane: add host memory mapping code Stefan Hajnoczi
@ 2012-12-05 20:47 ` Stefan Hajnoczi
2012-12-06 11:22 ` Michael S. Tsirkin
2012-12-07 14:07 ` Kevin Wolf
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 05/11] dataplane: add event loop Stefan Hajnoczi
` (8 subsequent siblings)
12 siblings, 2 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-05 20:47 UTC (permalink / raw)
To: qemu-devel
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
The virtio-blk-data-plane cannot access memory using the usual QEMU
functions since it executes outside the global mutex and the memory APIs
are this time are not thread-safe.
This patch introduces a virtqueue module based on the kernel's vhost
vring code. The trick is that we map guest memory ahead of time and
access it cheaply outside the global mutex.
Once the hardware emulation code can execute outside the global mutex it
will be possible to drop this code.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/Makefile.objs | 2 +-
hw/dataplane/Makefile.objs | 2 +-
hw/dataplane/vring.c | 361 +++++++++++++++++++++++++++++++++++++++++++++
hw/dataplane/vring.h | 63 ++++++++
trace-events | 3 +
5 files changed, 429 insertions(+), 2 deletions(-)
create mode 100644 hw/dataplane/vring.c
create mode 100644 hw/dataplane/vring.h
diff --git a/hw/Makefile.objs b/hw/Makefile.objs
index d581d8d..cec84bc 100644
--- a/hw/Makefile.objs
+++ b/hw/Makefile.objs
@@ -1,4 +1,4 @@
-common-obj-y = usb/ ide/
+common-obj-y = usb/ ide/ dataplane/
common-obj-y += loader.o
common-obj-$(CONFIG_VIRTIO) += virtio-console.o
common-obj-$(CONFIG_VIRTIO) += virtio-rng.o
diff --git a/hw/dataplane/Makefile.objs b/hw/dataplane/Makefile.objs
index 8c8dea1..34e6d57 100644
--- a/hw/dataplane/Makefile.objs
+++ b/hw/dataplane/Makefile.objs
@@ -1,3 +1,3 @@
ifeq ($(CONFIG_VIRTIO), y)
-common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o
+common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o
endif
diff --git a/hw/dataplane/vring.c b/hw/dataplane/vring.c
new file mode 100644
index 0000000..8321c70
--- /dev/null
+++ b/hw/dataplane/vring.c
@@ -0,0 +1,361 @@
+/* Copyright 2012 Red Hat, Inc.
+ * Copyright IBM, Corp. 2012
+ *
+ * Based on Linux 2.6.39 vhost code:
+ * Copyright (C) 2009 Red Hat, Inc.
+ * Copyright (C) 2006 Rusty Russell IBM Corporation
+ *
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ * Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * Inspiration, some code, and most witty comments come from
+ * Documentation/virtual/lguest/lguest.c, by Rusty Russell
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ */
+
+#include "trace.h"
+#include "hw/dataplane/vring.h"
+
+/* Map the guest's vring to host memory */
+bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
+{
+ hwaddr vring_addr = virtio_queue_get_ring_addr(vdev, n);
+ hwaddr vring_size = virtio_queue_get_ring_size(vdev, n);
+ void *vring_ptr;
+
+ vring->broken = false;
+
+ hostmem_init(&vring->hostmem);
+ vring_ptr = hostmem_lookup(&vring->hostmem, vring_addr, vring_size, true);
+ if (!vring_ptr) {
+ error_report("Failed to map vring "
+ "addr %#" HWADDR_PRIx " size %" HWADDR_PRIu,
+ vring_addr, vring_size);
+ vring->broken = true;
+ return false;
+ }
+
+ vring_init(&vring->vr, virtio_queue_get_num(vdev, n), vring_ptr, 4096);
+
+ vring->last_avail_idx = 0;
+ vring->last_used_idx = 0;
+ vring->signalled_used = 0;
+ vring->signalled_used_valid = false;
+
+ trace_vring_setup(virtio_queue_get_ring_addr(vdev, n),
+ vring->vr.desc, vring->vr.avail, vring->vr.used);
+ return true;
+}
+
+void vring_teardown(Vring *vring)
+{
+ hostmem_finalize(&vring->hostmem);
+}
+
+/* Disable guest->host notifies */
+void vring_disable_notification(VirtIODevice *vdev, Vring *vring)
+{
+ if (!(vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX))) {
+ vring->vr.used->flags |= VRING_USED_F_NO_NOTIFY;
+ }
+}
+
+/* Enable guest->host notifies
+ *
+ * Return true if the vring is empty, false if there are more requests.
+ */
+bool vring_enable_notification(VirtIODevice *vdev, Vring *vring)
+{
+ if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) {
+ vring_avail_event(&vring->vr) = vring->vr.avail->idx;
+ } else {
+ vring->vr.used->flags &= ~VRING_USED_F_NO_NOTIFY;
+ }
+ smp_mb(); /* ensure update is seen before reading avail_idx */
+ return !vring_more_avail(vring);
+}
+
+/* This is stolen from linux/drivers/vhost/vhost.c:vhost_notify() */
+bool vring_should_notify(VirtIODevice *vdev, Vring *vring)
+{
+ uint16_t old, new;
+ bool v;
+ /* Flush out used index updates. This is paired
+ * with the barrier that the Guest executes when enabling
+ * interrupts. */
+ smp_mb();
+
+ if ((vdev->guest_features & VIRTIO_F_NOTIFY_ON_EMPTY) &&
+ unlikely(vring->vr.avail->idx == vring->last_avail_idx)) {
+ return true;
+ }
+
+ if (!(vdev->guest_features & VIRTIO_RING_F_EVENT_IDX)) {
+ return !(vring->vr.avail->flags & VRING_AVAIL_F_NO_INTERRUPT);
+ }
+ old = vring->signalled_used;
+ v = vring->signalled_used_valid;
+ new = vring->signalled_used = vring->last_used_idx;
+ vring->signalled_used_valid = true;
+
+ if (unlikely(!v)) {
+ return true;
+ }
+
+ return vring_need_event(vring_used_event(&vring->vr), new, old);
+}
+
+/* This is stolen from linux/drivers/vhost/vhost.c. */
+static int get_indirect(Vring *vring,
+ struct iovec iov[], struct iovec *iov_end,
+ unsigned int *out_num, unsigned int *in_num,
+ struct vring_desc *indirect)
+{
+ struct vring_desc desc;
+ unsigned int i = 0, count, found = 0;
+
+ /* Sanity check */
+ if (unlikely(indirect->len % sizeof(desc))) {
+ error_report("Invalid length in indirect descriptor: "
+ "len %#x not multiple of %#zx",
+ indirect->len, sizeof(desc));
+ vring->broken = true;
+ return -EFAULT;
+ }
+
+ count = indirect->len / sizeof(desc);
+ /* Buffers are chained via a 16 bit next field, so
+ * we can have at most 2^16 of these. */
+ if (unlikely(count > USHRT_MAX + 1)) {
+ error_report("Indirect buffer length too big: %d", indirect->len);
+ vring->broken = true;
+ return -EFAULT;
+ }
+
+ do {
+ struct vring_desc *desc_ptr;
+
+ /* Translate indirect descriptor */
+ desc_ptr = hostmem_lookup(&vring->hostmem,
+ indirect->addr + found * sizeof(desc),
+ sizeof(desc), false);
+ if (!desc_ptr) {
+ error_report("Failed to map indirect descriptor "
+ "addr %#" PRIx64 " len %zu",
+ (uint64_t)indirect->addr + found * sizeof(desc),
+ sizeof(desc));
+ vring->broken = true;
+ return -EFAULT;
+ }
+ desc = *desc_ptr;
+
+ /* Ensure descriptor has been loaded before accessing fields */
+ barrier(); /* read_barrier_depends(); */
+
+ if (unlikely(++found > count)) {
+ error_report("Loop detected: last one at %u "
+ "indirect size %u", i, count);
+ vring->broken = true;
+ return -EFAULT;
+ }
+
+ if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
+ error_report("Nested indirect descriptor");
+ vring->broken = true;
+ return -EFAULT;
+ }
+
+ /* Stop for now if there are not enough iovecs available. */
+ if (iov >= iov_end) {
+ return -ENOBUFS;
+ }
+
+ iov->iov_base = hostmem_lookup(&vring->hostmem, desc.addr, desc.len,
+ desc.flags & VRING_DESC_F_WRITE);
+ if (!iov->iov_base) {
+ error_report("Failed to map indirect descriptor"
+ "addr %#" PRIx64 " len %u",
+ (uint64_t)desc.addr, desc.len);
+ vring->broken = true;
+ return -EFAULT;
+ }
+ iov->iov_len = desc.len;
+ iov++;
+
+ /* If this is an input descriptor, increment that count. */
+ if (desc.flags & VRING_DESC_F_WRITE) {
+ *in_num += 1;
+ } else {
+ /* If it's an output descriptor, they're all supposed
+ * to come before any input descriptors. */
+ if (unlikely(*in_num)) {
+ error_report("Indirect descriptor "
+ "has out after in: idx %u", i);
+ vring->broken = true;
+ return -EFAULT;
+ }
+ *out_num += 1;
+ }
+ i = desc.next;
+ } while (desc.flags & VRING_DESC_F_NEXT);
+ return 0;
+}
+
+/* This looks in the virtqueue and for the first available buffer, and converts
+ * it to an iovec for convenient access. Since descriptors consist of some
+ * number of output then some number of input descriptors, it's actually two
+ * iovecs, but we pack them into one and note how many of each there were.
+ *
+ * This function returns the descriptor number found, or vq->num (which is
+ * never a valid descriptor number) if none was found. A negative code is
+ * returned on error.
+ *
+ * Stolen from linux/drivers/vhost/vhost.c.
+ */
+int vring_pop(VirtIODevice *vdev, Vring *vring,
+ struct iovec iov[], struct iovec *iov_end,
+ unsigned int *out_num, unsigned int *in_num)
+{
+ struct vring_desc desc;
+ unsigned int i, head, found = 0, num = vring->vr.num;
+ uint16_t avail_idx, last_avail_idx;
+
+ /* If there was a fatal error then refuse operation */
+ if (vring->broken) {
+ return -EFAULT;
+ }
+
+ /* Check it isn't doing very strange things with descriptor numbers. */
+ last_avail_idx = vring->last_avail_idx;
+ avail_idx = vring->vr.avail->idx;
+ barrier(); /* load indices now and not again later */
+
+ if (unlikely((uint16_t)(avail_idx - last_avail_idx) > num)) {
+ error_report("Guest moved used index from %u to %u",
+ last_avail_idx, avail_idx);
+ vring->broken = true;
+ return -EFAULT;
+ }
+
+ /* If there's nothing new since last we looked. */
+ if (avail_idx == last_avail_idx) {
+ return -EAGAIN;
+ }
+
+ /* Only get avail ring entries after they have been exposed by guest. */
+ smp_rmb();
+
+ /* Grab the next descriptor number they're advertising, and increment
+ * the index we've seen. */
+ head = vring->vr.avail->ring[last_avail_idx % num];
+
+ /* If their number is silly, that's an error. */
+ if (unlikely(head >= num)) {
+ error_report("Guest says index %u > %u is available", head, num);
+ vring->broken = true;
+ return -EFAULT;
+ }
+
+ if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) {
+ vring_avail_event(&vring->vr) = vring->vr.avail->idx;
+ }
+
+ /* When we start there are none of either input nor output. */
+ *out_num = *in_num = 0;
+
+ i = head;
+ do {
+ if (unlikely(i >= num)) {
+ error_report("Desc index is %u > %u, head = %u", i, num, head);
+ vring->broken = true;
+ return -EFAULT;
+ }
+ if (unlikely(++found > num)) {
+ error_report("Loop detected: last one at %u vq size %u head %u",
+ i, num, head);
+ vring->broken = true;
+ return -EFAULT;
+ }
+ desc = vring->vr.desc[i];
+
+ /* Ensure descriptor is loaded before accessing fields */
+ barrier();
+
+ if (desc.flags & VRING_DESC_F_INDIRECT) {
+ int ret = get_indirect(vring, iov, iov_end, out_num, in_num, &desc);
+ if (ret < 0) {
+ return ret;
+ }
+ continue;
+ }
+
+ /* If there are not enough iovecs left, stop for now. The caller
+ * should check if there are more descs available once they have dealt
+ * with the current set.
+ */
+ if (iov >= iov_end) {
+ return -ENOBUFS;
+ }
+
+ iov->iov_base = hostmem_lookup(&vring->hostmem, desc.addr, desc.len,
+ desc.flags & VRING_DESC_F_WRITE);
+ if (!iov->iov_base) {
+ error_report("Failed to map vring desc addr %#" PRIx64 " len %u",
+ (uint64_t)desc.addr, desc.len);
+ vring->broken = true;
+ return -EFAULT;
+ }
+ iov->iov_len = desc.len;
+ iov++;
+
+ if (desc.flags & VRING_DESC_F_WRITE) {
+ /* If this is an input descriptor,
+ * increment that count. */
+ *in_num += 1;
+ } else {
+ /* If it's an output descriptor, they're all supposed
+ * to come before any input descriptors. */
+ if (unlikely(*in_num)) {
+ error_report("Descriptor has out after in: idx %d", i);
+ vring->broken = true;
+ return -EFAULT;
+ }
+ *out_num += 1;
+ }
+ i = desc.next;
+ } while (desc.flags & VRING_DESC_F_NEXT);
+
+ /* On success, increment avail index. */
+ vring->last_avail_idx++;
+ return head;
+}
+
+/* After we've used one of their buffers, we tell them about it.
+ *
+ * Stolen from linux/drivers/vhost/vhost.c.
+ */
+void vring_push(Vring *vring, unsigned int head, int len)
+{
+ struct vring_used_elem *used;
+ uint16_t new;
+
+ /* Don't touch vring if a fatal error occurred */
+ if (vring->broken) {
+ return;
+ }
+
+ /* The virtqueue contains a ring of used buffers. Get a pointer to the
+ * next entry in that used ring. */
+ used = &vring->vr.used->ring[vring->last_used_idx % vring->vr.num];
+ used->id = head;
+ used->len = len;
+
+ /* Make sure buffer is written before we update index. */
+ smp_wmb();
+
+ new = vring->vr.used->idx = ++vring->last_used_idx;
+ if (unlikely((int16_t)(new - vring->signalled_used) < (uint16_t)1)) {
+ vring->signalled_used_valid = false;
+ }
+}
diff --git a/hw/dataplane/vring.h b/hw/dataplane/vring.h
new file mode 100644
index 0000000..1a1164a
--- /dev/null
+++ b/hw/dataplane/vring.h
@@ -0,0 +1,63 @@
+/* Copyright 2012 Red Hat, Inc. and/or its affiliates
+ * Copyright IBM, Corp. 2012
+ *
+ * Based on Linux 2.6.39 vhost code:
+ * Copyright (C) 2009 Red Hat, Inc.
+ * Copyright (C) 2006 Rusty Russell IBM Corporation
+ *
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ * Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * Inspiration, some code, and most witty comments come from
+ * Documentation/virtual/lguest/lguest.c, by Rusty Russell
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ */
+
+#ifndef VRING_H
+#define VRING_H
+
+#include <linux/virtio_ring.h>
+#include "qemu-common.h"
+#include "qemu-barrier.h"
+#include "hw/dataplane/hostmem.h"
+#include "hw/virtio.h"
+
+typedef struct {
+ Hostmem hostmem; /* guest memory mapper */
+ struct vring vr; /* virtqueue vring mapped to host memory */
+ uint16_t last_avail_idx; /* last processed avail ring index */
+ uint16_t last_used_idx; /* last processed used ring index */
+ uint16_t signalled_used; /* EVENT_IDX state */
+ bool signalled_used_valid;
+ bool broken; /* was there a fatal error? */
+} Vring;
+
+static inline unsigned int vring_get_num(Vring *vring)
+{
+ return vring->vr.num;
+}
+
+/* Are there more descriptors available? */
+static inline bool vring_more_avail(Vring *vring)
+{
+ return vring->vr.avail->idx != vring->last_avail_idx;
+}
+
+/* Fail future vring_pop() and vring_push() calls until reset */
+static inline void vring_set_broken(Vring *vring)
+{
+ vring->broken = true;
+}
+
+bool vring_setup(Vring *vring, VirtIODevice *vdev, int n);
+void vring_teardown(Vring *vring);
+void vring_disable_notification(VirtIODevice *vdev, Vring *vring);
+bool vring_enable_notification(VirtIODevice *vdev, Vring *vring);
+bool vring_should_notify(VirtIODevice *vdev, Vring *vring);
+int vring_pop(VirtIODevice *vdev, Vring *vring,
+ struct iovec iov[], struct iovec *iov_end,
+ unsigned int *out_num, unsigned int *in_num);
+void vring_push(Vring *vring, unsigned int head, int len);
+
+#endif /* VRING_H */
diff --git a/trace-events b/trace-events
index 6c6cbf1..a9a791b 100644
--- a/trace-events
+++ b/trace-events
@@ -98,6 +98,9 @@ virtio_blk_rw_complete(void *req, int ret) "req %p ret %d"
virtio_blk_handle_write(void *req, uint64_t sector, size_t nsectors) "req %p sector %"PRIu64" nsectors %zu"
virtio_blk_handle_read(void *req, uint64_t sector, size_t nsectors) "req %p sector %"PRIu64" nsectors %zu"
+# hw/dataplane/vring.c
+vring_setup(uint64_t physical, void *desc, void *avail, void *used) "vring physical %#"PRIx64" desc %p avail %p used %p"
+
# thread-pool.c
thread_pool_submit(void *req, void *opaque) "req %p opaque %p"
thread_pool_complete(void *req, void *opaque, int ret) "req %p opaque %p ret %d"
--
1.8.0.1
^ permalink raw reply related [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 04/11] dataplane: add virtqueue vring code
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 04/11] dataplane: add virtqueue vring code Stefan Hajnoczi
@ 2012-12-06 11:22 ` Michael S. Tsirkin
2012-12-06 12:53 ` Stefan Hajnoczi
2012-12-07 14:07 ` Kevin Wolf
1 sibling, 1 reply; 34+ messages in thread
From: Michael S. Tsirkin @ 2012-12-06 11:22 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Kevin Wolf, Anthony Liguori, qemu-devel, Blue Swirl, khoa,
Paolo Bonzini, asias
On Wed, Dec 05, 2012 at 09:47:03PM +0100, Stefan Hajnoczi wrote:
> The virtio-blk-data-plane cannot access memory using the usual QEMU
> functions since it executes outside the global mutex and the memory APIs
> are this time are not thread-safe.
>
> This patch introduces a virtqueue module based on the kernel's vhost
> vring code. The trick is that we map guest memory ahead of time and
> access it cheaply outside the global mutex.
Question: can virtio.c be reworked to use vring.c instead?
The cost of keeping an extra memory listener around seems negligeable.
The only issue I see is around dirty tracking for used ring writes.
Maybe we could add a callback for this?
>
> Once the hardware emulation code can execute outside the global mutex it
> will be possible to drop this code.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> hw/Makefile.objs | 2 +-
> hw/dataplane/Makefile.objs | 2 +-
> hw/dataplane/vring.c | 361 +++++++++++++++++++++++++++++++++++++++++++++
> hw/dataplane/vring.h | 63 ++++++++
> trace-events | 3 +
> 5 files changed, 429 insertions(+), 2 deletions(-)
> create mode 100644 hw/dataplane/vring.c
> create mode 100644 hw/dataplane/vring.h
>
> diff --git a/hw/Makefile.objs b/hw/Makefile.objs
> index d581d8d..cec84bc 100644
> --- a/hw/Makefile.objs
> +++ b/hw/Makefile.objs
> @@ -1,4 +1,4 @@
> -common-obj-y = usb/ ide/
> +common-obj-y = usb/ ide/ dataplane/
> common-obj-y += loader.o
> common-obj-$(CONFIG_VIRTIO) += virtio-console.o
> common-obj-$(CONFIG_VIRTIO) += virtio-rng.o
> diff --git a/hw/dataplane/Makefile.objs b/hw/dataplane/Makefile.objs
> index 8c8dea1..34e6d57 100644
> --- a/hw/dataplane/Makefile.objs
> +++ b/hw/dataplane/Makefile.objs
> @@ -1,3 +1,3 @@
> ifeq ($(CONFIG_VIRTIO), y)
> -common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o
> +common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o
> endif
> diff --git a/hw/dataplane/vring.c b/hw/dataplane/vring.c
> new file mode 100644
> index 0000000..8321c70
> --- /dev/null
> +++ b/hw/dataplane/vring.c
> @@ -0,0 +1,361 @@
> +/* Copyright 2012 Red Hat, Inc.
> + * Copyright IBM, Corp. 2012
> + *
> + * Based on Linux 2.6.39 vhost code:
> + * Copyright (C) 2009 Red Hat, Inc.
> + * Copyright (C) 2006 Rusty Russell IBM Corporation
> + *
> + * Author: Michael S. Tsirkin <mst@redhat.com>
> + * Stefan Hajnoczi <stefanha@redhat.com>
> + *
> + * Inspiration, some code, and most witty comments come from
> + * Documentation/virtual/lguest/lguest.c, by Rusty Russell
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
> + */
> +
> +#include "trace.h"
> +#include "hw/dataplane/vring.h"
> +
> +/* Map the guest's vring to host memory */
> +bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
> +{
> + hwaddr vring_addr = virtio_queue_get_ring_addr(vdev, n);
> + hwaddr vring_size = virtio_queue_get_ring_size(vdev, n);
> + void *vring_ptr;
> +
> + vring->broken = false;
> +
> + hostmem_init(&vring->hostmem);
> + vring_ptr = hostmem_lookup(&vring->hostmem, vring_addr, vring_size, true);
> + if (!vring_ptr) {
> + error_report("Failed to map vring "
> + "addr %#" HWADDR_PRIx " size %" HWADDR_PRIu,
> + vring_addr, vring_size);
> + vring->broken = true;
> + return false;
> + }
> +
> + vring_init(&vring->vr, virtio_queue_get_num(vdev, n), vring_ptr, 4096);
> +
> + vring->last_avail_idx = 0;
> + vring->last_used_idx = 0;
> + vring->signalled_used = 0;
> + vring->signalled_used_valid = false;
> +
> + trace_vring_setup(virtio_queue_get_ring_addr(vdev, n),
> + vring->vr.desc, vring->vr.avail, vring->vr.used);
> + return true;
> +}
> +
> +void vring_teardown(Vring *vring)
> +{
> + hostmem_finalize(&vring->hostmem);
> +}
> +
> +/* Disable guest->host notifies */
> +void vring_disable_notification(VirtIODevice *vdev, Vring *vring)
> +{
> + if (!(vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX))) {
> + vring->vr.used->flags |= VRING_USED_F_NO_NOTIFY;
> + }
> +}
> +
> +/* Enable guest->host notifies
> + *
> + * Return true if the vring is empty, false if there are more requests.
> + */
> +bool vring_enable_notification(VirtIODevice *vdev, Vring *vring)
> +{
> + if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) {
> + vring_avail_event(&vring->vr) = vring->vr.avail->idx;
> + } else {
> + vring->vr.used->flags &= ~VRING_USED_F_NO_NOTIFY;
> + }
> + smp_mb(); /* ensure update is seen before reading avail_idx */
> + return !vring_more_avail(vring);
> +}
> +
> +/* This is stolen from linux/drivers/vhost/vhost.c:vhost_notify() */
> +bool vring_should_notify(VirtIODevice *vdev, Vring *vring)
> +{
> + uint16_t old, new;
> + bool v;
> + /* Flush out used index updates. This is paired
> + * with the barrier that the Guest executes when enabling
> + * interrupts. */
> + smp_mb();
> +
> + if ((vdev->guest_features & VIRTIO_F_NOTIFY_ON_EMPTY) &&
> + unlikely(vring->vr.avail->idx == vring->last_avail_idx)) {
> + return true;
> + }
> +
> + if (!(vdev->guest_features & VIRTIO_RING_F_EVENT_IDX)) {
> + return !(vring->vr.avail->flags & VRING_AVAIL_F_NO_INTERRUPT);
> + }
> + old = vring->signalled_used;
> + v = vring->signalled_used_valid;
> + new = vring->signalled_used = vring->last_used_idx;
> + vring->signalled_used_valid = true;
> +
> + if (unlikely(!v)) {
> + return true;
> + }
> +
> + return vring_need_event(vring_used_event(&vring->vr), new, old);
> +}
> +
> +/* This is stolen from linux/drivers/vhost/vhost.c. */
> +static int get_indirect(Vring *vring,
> + struct iovec iov[], struct iovec *iov_end,
> + unsigned int *out_num, unsigned int *in_num,
> + struct vring_desc *indirect)
> +{
> + struct vring_desc desc;
> + unsigned int i = 0, count, found = 0;
> +
> + /* Sanity check */
> + if (unlikely(indirect->len % sizeof(desc))) {
> + error_report("Invalid length in indirect descriptor: "
> + "len %#x not multiple of %#zx",
> + indirect->len, sizeof(desc));
> + vring->broken = true;
> + return -EFAULT;
> + }
> +
> + count = indirect->len / sizeof(desc);
> + /* Buffers are chained via a 16 bit next field, so
> + * we can have at most 2^16 of these. */
> + if (unlikely(count > USHRT_MAX + 1)) {
> + error_report("Indirect buffer length too big: %d", indirect->len);
> + vring->broken = true;
> + return -EFAULT;
> + }
> +
> + do {
> + struct vring_desc *desc_ptr;
> +
> + /* Translate indirect descriptor */
> + desc_ptr = hostmem_lookup(&vring->hostmem,
> + indirect->addr + found * sizeof(desc),
> + sizeof(desc), false);
> + if (!desc_ptr) {
> + error_report("Failed to map indirect descriptor "
> + "addr %#" PRIx64 " len %zu",
> + (uint64_t)indirect->addr + found * sizeof(desc),
> + sizeof(desc));
> + vring->broken = true;
> + return -EFAULT;
> + }
> + desc = *desc_ptr;
> +
> + /* Ensure descriptor has been loaded before accessing fields */
> + barrier(); /* read_barrier_depends(); */
> +
> + if (unlikely(++found > count)) {
> + error_report("Loop detected: last one at %u "
> + "indirect size %u", i, count);
> + vring->broken = true;
> + return -EFAULT;
> + }
> +
> + if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
> + error_report("Nested indirect descriptor");
> + vring->broken = true;
> + return -EFAULT;
> + }
> +
> + /* Stop for now if there are not enough iovecs available. */
> + if (iov >= iov_end) {
> + return -ENOBUFS;
> + }
> +
> + iov->iov_base = hostmem_lookup(&vring->hostmem, desc.addr, desc.len,
> + desc.flags & VRING_DESC_F_WRITE);
> + if (!iov->iov_base) {
> + error_report("Failed to map indirect descriptor"
> + "addr %#" PRIx64 " len %u",
> + (uint64_t)desc.addr, desc.len);
> + vring->broken = true;
> + return -EFAULT;
> + }
> + iov->iov_len = desc.len;
> + iov++;
> +
> + /* If this is an input descriptor, increment that count. */
> + if (desc.flags & VRING_DESC_F_WRITE) {
> + *in_num += 1;
> + } else {
> + /* If it's an output descriptor, they're all supposed
> + * to come before any input descriptors. */
> + if (unlikely(*in_num)) {
> + error_report("Indirect descriptor "
> + "has out after in: idx %u", i);
> + vring->broken = true;
> + return -EFAULT;
> + }
> + *out_num += 1;
> + }
> + i = desc.next;
> + } while (desc.flags & VRING_DESC_F_NEXT);
> + return 0;
> +}
> +
> +/* This looks in the virtqueue and for the first available buffer, and converts
> + * it to an iovec for convenient access. Since descriptors consist of some
> + * number of output then some number of input descriptors, it's actually two
> + * iovecs, but we pack them into one and note how many of each there were.
> + *
> + * This function returns the descriptor number found, or vq->num (which is
> + * never a valid descriptor number) if none was found. A negative code is
> + * returned on error.
> + *
> + * Stolen from linux/drivers/vhost/vhost.c.
> + */
> +int vring_pop(VirtIODevice *vdev, Vring *vring,
> + struct iovec iov[], struct iovec *iov_end,
> + unsigned int *out_num, unsigned int *in_num)
> +{
> + struct vring_desc desc;
> + unsigned int i, head, found = 0, num = vring->vr.num;
> + uint16_t avail_idx, last_avail_idx;
> +
> + /* If there was a fatal error then refuse operation */
> + if (vring->broken) {
> + return -EFAULT;
> + }
> +
> + /* Check it isn't doing very strange things with descriptor numbers. */
> + last_avail_idx = vring->last_avail_idx;
> + avail_idx = vring->vr.avail->idx;
> + barrier(); /* load indices now and not again later */
> +
> + if (unlikely((uint16_t)(avail_idx - last_avail_idx) > num)) {
> + error_report("Guest moved used index from %u to %u",
> + last_avail_idx, avail_idx);
> + vring->broken = true;
> + return -EFAULT;
> + }
> +
> + /* If there's nothing new since last we looked. */
> + if (avail_idx == last_avail_idx) {
> + return -EAGAIN;
> + }
> +
> + /* Only get avail ring entries after they have been exposed by guest. */
> + smp_rmb();
> +
> + /* Grab the next descriptor number they're advertising, and increment
> + * the index we've seen. */
> + head = vring->vr.avail->ring[last_avail_idx % num];
> +
> + /* If their number is silly, that's an error. */
> + if (unlikely(head >= num)) {
> + error_report("Guest says index %u > %u is available", head, num);
> + vring->broken = true;
> + return -EFAULT;
> + }
> +
> + if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) {
> + vring_avail_event(&vring->vr) = vring->vr.avail->idx;
> + }
> +
> + /* When we start there are none of either input nor output. */
> + *out_num = *in_num = 0;
> +
> + i = head;
> + do {
> + if (unlikely(i >= num)) {
> + error_report("Desc index is %u > %u, head = %u", i, num, head);
> + vring->broken = true;
> + return -EFAULT;
> + }
> + if (unlikely(++found > num)) {
> + error_report("Loop detected: last one at %u vq size %u head %u",
> + i, num, head);
> + vring->broken = true;
> + return -EFAULT;
> + }
> + desc = vring->vr.desc[i];
> +
> + /* Ensure descriptor is loaded before accessing fields */
> + barrier();
> +
> + if (desc.flags & VRING_DESC_F_INDIRECT) {
> + int ret = get_indirect(vring, iov, iov_end, out_num, in_num, &desc);
> + if (ret < 0) {
> + return ret;
> + }
> + continue;
> + }
> +
> + /* If there are not enough iovecs left, stop for now. The caller
> + * should check if there are more descs available once they have dealt
> + * with the current set.
> + */
> + if (iov >= iov_end) {
> + return -ENOBUFS;
> + }
> +
> + iov->iov_base = hostmem_lookup(&vring->hostmem, desc.addr, desc.len,
> + desc.flags & VRING_DESC_F_WRITE);
> + if (!iov->iov_base) {
> + error_report("Failed to map vring desc addr %#" PRIx64 " len %u",
> + (uint64_t)desc.addr, desc.len);
> + vring->broken = true;
> + return -EFAULT;
> + }
> + iov->iov_len = desc.len;
> + iov++;
> +
> + if (desc.flags & VRING_DESC_F_WRITE) {
> + /* If this is an input descriptor,
> + * increment that count. */
> + *in_num += 1;
> + } else {
> + /* If it's an output descriptor, they're all supposed
> + * to come before any input descriptors. */
> + if (unlikely(*in_num)) {
> + error_report("Descriptor has out after in: idx %d", i);
> + vring->broken = true;
> + return -EFAULT;
> + }
> + *out_num += 1;
> + }
> + i = desc.next;
> + } while (desc.flags & VRING_DESC_F_NEXT);
> +
> + /* On success, increment avail index. */
> + vring->last_avail_idx++;
> + return head;
> +}
> +
> +/* After we've used one of their buffers, we tell them about it.
> + *
> + * Stolen from linux/drivers/vhost/vhost.c.
> + */
> +void vring_push(Vring *vring, unsigned int head, int len)
> +{
> + struct vring_used_elem *used;
> + uint16_t new;
> +
> + /* Don't touch vring if a fatal error occurred */
> + if (vring->broken) {
> + return;
> + }
> +
> + /* The virtqueue contains a ring of used buffers. Get a pointer to the
> + * next entry in that used ring. */
> + used = &vring->vr.used->ring[vring->last_used_idx % vring->vr.num];
> + used->id = head;
> + used->len = len;
> +
> + /* Make sure buffer is written before we update index. */
> + smp_wmb();
> +
> + new = vring->vr.used->idx = ++vring->last_used_idx;
> + if (unlikely((int16_t)(new - vring->signalled_used) < (uint16_t)1)) {
> + vring->signalled_used_valid = false;
> + }
> +}
> diff --git a/hw/dataplane/vring.h b/hw/dataplane/vring.h
> new file mode 100644
> index 0000000..1a1164a
> --- /dev/null
> +++ b/hw/dataplane/vring.h
> @@ -0,0 +1,63 @@
> +/* Copyright 2012 Red Hat, Inc. and/or its affiliates
> + * Copyright IBM, Corp. 2012
> + *
> + * Based on Linux 2.6.39 vhost code:
> + * Copyright (C) 2009 Red Hat, Inc.
> + * Copyright (C) 2006 Rusty Russell IBM Corporation
> + *
> + * Author: Michael S. Tsirkin <mst@redhat.com>
> + * Stefan Hajnoczi <stefanha@redhat.com>
> + *
> + * Inspiration, some code, and most witty comments come from
> + * Documentation/virtual/lguest/lguest.c, by Rusty Russell
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
> + */
> +
> +#ifndef VRING_H
> +#define VRING_H
> +
> +#include <linux/virtio_ring.h>
> +#include "qemu-common.h"
> +#include "qemu-barrier.h"
> +#include "hw/dataplane/hostmem.h"
> +#include "hw/virtio.h"
> +
> +typedef struct {
> + Hostmem hostmem; /* guest memory mapper */
> + struct vring vr; /* virtqueue vring mapped to host memory */
> + uint16_t last_avail_idx; /* last processed avail ring index */
> + uint16_t last_used_idx; /* last processed used ring index */
> + uint16_t signalled_used; /* EVENT_IDX state */
> + bool signalled_used_valid;
> + bool broken; /* was there a fatal error? */
> +} Vring;
> +
> +static inline unsigned int vring_get_num(Vring *vring)
> +{
> + return vring->vr.num;
> +}
> +
> +/* Are there more descriptors available? */
> +static inline bool vring_more_avail(Vring *vring)
> +{
> + return vring->vr.avail->idx != vring->last_avail_idx;
> +}
> +
> +/* Fail future vring_pop() and vring_push() calls until reset */
> +static inline void vring_set_broken(Vring *vring)
> +{
> + vring->broken = true;
> +}
> +
> +bool vring_setup(Vring *vring, VirtIODevice *vdev, int n);
> +void vring_teardown(Vring *vring);
> +void vring_disable_notification(VirtIODevice *vdev, Vring *vring);
> +bool vring_enable_notification(VirtIODevice *vdev, Vring *vring);
> +bool vring_should_notify(VirtIODevice *vdev, Vring *vring);
> +int vring_pop(VirtIODevice *vdev, Vring *vring,
> + struct iovec iov[], struct iovec *iov_end,
> + unsigned int *out_num, unsigned int *in_num);
> +void vring_push(Vring *vring, unsigned int head, int len);
> +
> +#endif /* VRING_H */
> diff --git a/trace-events b/trace-events
> index 6c6cbf1..a9a791b 100644
> --- a/trace-events
> +++ b/trace-events
> @@ -98,6 +98,9 @@ virtio_blk_rw_complete(void *req, int ret) "req %p ret %d"
> virtio_blk_handle_write(void *req, uint64_t sector, size_t nsectors) "req %p sector %"PRIu64" nsectors %zu"
> virtio_blk_handle_read(void *req, uint64_t sector, size_t nsectors) "req %p sector %"PRIu64" nsectors %zu"
>
> +# hw/dataplane/vring.c
> +vring_setup(uint64_t physical, void *desc, void *avail, void *used) "vring physical %#"PRIx64" desc %p avail %p used %p"
> +
> # thread-pool.c
> thread_pool_submit(void *req, void *opaque) "req %p opaque %p"
> thread_pool_complete(void *req, void *opaque, int ret) "req %p opaque %p ret %d"
> --
> 1.8.0.1
^ permalink raw reply [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 04/11] dataplane: add virtqueue vring code
2012-12-06 11:22 ` Michael S. Tsirkin
@ 2012-12-06 12:53 ` Stefan Hajnoczi
0 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-06 12:53 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Kevin Wolf, Anthony Liguori, qemu-devel, Blue Swirl, khoa,
Paolo Bonzini, asias
On Thu, Dec 06, 2012 at 01:22:29PM +0200, Michael S. Tsirkin wrote:
> On Wed, Dec 05, 2012 at 09:47:03PM +0100, Stefan Hajnoczi wrote:
> > The virtio-blk-data-plane cannot access memory using the usual QEMU
> > functions since it executes outside the global mutex and the memory APIs
> > are this time are not thread-safe.
> >
> > This patch introduces a virtqueue module based on the kernel's vhost
> > vring code. The trick is that we map guest memory ahead of time and
> > access it cheaply outside the global mutex.
>
> Question: can virtio.c be reworked to use vring.c instead?
> The cost of keeping an extra memory listener around seems negligeable.
> The only issue I see is around dirty tracking for used ring writes.
> Maybe we could add a callback for this?
virtio.c and dataplane/vring.c will be unified but I think it's beyond
the scope of this series. This is the thread-safe memory API
refactoring we discussed.
Stefan
^ permalink raw reply [flat|nested] 34+ messages in thread
* Re: [Qemu-devel] [PATCH v5 04/11] dataplane: add virtqueue vring code
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 04/11] dataplane: add virtqueue vring code Stefan Hajnoczi
2012-12-06 11:22 ` Michael S. Tsirkin
@ 2012-12-07 14:07 ` Kevin Wolf
2012-12-07 14:46 ` Stefan Hajnoczi
1 sibling, 1 reply; 34+ messages in thread
From: Kevin Wolf @ 2012-12-07 14:07 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Anthony Liguori, Michael S. Tsirkin, qemu-devel, Blue Swirl, khoa,
Paolo Bonzini, asias
Am 05.12.2012 21:47, schrieb Stefan Hajnoczi:
> The virtio-blk-data-plane cannot access memory using the usual QEMU
> functions since it executes outside the global mutex and the memory APIs
> are this time are not thread-safe.
>
> This patch introduces a virtqueue module based on the kernel's vhost
> vring code. The trick is that we map guest memory ahead of time and
> access it cheaply outside the global mutex.
>
> Once the hardware emulation code can execute outside the global mutex it
> will be possible to drop this code.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> hw/Makefile.objs | 2 +-
> hw/dataplane/Makefile.objs | 2 +-
> hw/dataplane/vring.c | 361 +++++++++++++++++++++++++++++++++++++++++++++
> hw/dataplane/vring.h | 63 ++++++++
> trace-events | 3 +
> 5 files changed, 429 insertions(+), 2 deletions(-)
> create mode 100644 hw/dataplane/vring.c
> create mode 100644 hw/dataplane/vring.h
>
> diff --git a/hw/Makefile.objs b/hw/Makefile.objs
> index d581d8d..cec84bc 100644
> --- a/hw/Makefile.objs
> +++ b/hw/Makefile.objs
> @@ -1,4 +1,4 @@
> -common-obj-y = usb/ ide/
> +common-obj-y = usb/ ide/ dataplane/
> common-obj-y += loader.o
> common-obj-$(CONFIG_VIRTIO) += virtio-console.o
> common-obj-$(CONFIG_VIRTIO) += virtio-rng.o
Shouldn't this hunk be in patch 3?
Kevin
^ permalink raw reply [flat|nested] 34+ messages in thread
* Re: [Qemu-devel] [PATCH v5 04/11] dataplane: add virtqueue vring code
2012-12-07 14:07 ` Kevin Wolf
@ 2012-12-07 14:46 ` Stefan Hajnoczi
0 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-07 14:46 UTC (permalink / raw)
To: Kevin Wolf
Cc: Anthony Liguori, Michael S. Tsirkin, qemu-devel, Blue Swirl,
Khoa Huynh, Stefan Hajnoczi, Paolo Bonzini, Asias He
On Fri, Dec 7, 2012 at 3:07 PM, Kevin Wolf <kwolf@redhat.com> wrote:
> Am 05.12.2012 21:47, schrieb Stefan Hajnoczi:
>> The virtio-blk-data-plane cannot access memory using the usual QEMU
>> functions since it executes outside the global mutex and the memory APIs
>> are this time are not thread-safe.
>>
>> This patch introduces a virtqueue module based on the kernel's vhost
>> vring code. The trick is that we map guest memory ahead of time and
>> access it cheaply outside the global mutex.
>>
>> Once the hardware emulation code can execute outside the global mutex it
>> will be possible to drop this code.
>>
>> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
>> ---
>> hw/Makefile.objs | 2 +-
>> hw/dataplane/Makefile.objs | 2 +-
>> hw/dataplane/vring.c | 361 +++++++++++++++++++++++++++++++++++++++++++++
>> hw/dataplane/vring.h | 63 ++++++++
>> trace-events | 3 +
>> 5 files changed, 429 insertions(+), 2 deletions(-)
>> create mode 100644 hw/dataplane/vring.c
>> create mode 100644 hw/dataplane/vring.h
>>
>> diff --git a/hw/Makefile.objs b/hw/Makefile.objs
>> index d581d8d..cec84bc 100644
>> --- a/hw/Makefile.objs
>> +++ b/hw/Makefile.objs
>> @@ -1,4 +1,4 @@
>> -common-obj-y = usb/ ide/
>> +common-obj-y = usb/ ide/ dataplane/
>> common-obj-y += loader.o
>> common-obj-$(CONFIG_VIRTIO) += virtio-console.o
>> common-obj-$(CONFIG_VIRTIO) += virtio-rng.o
>
> Shouldn't this hunk be in patch 3?
Yes, I'll move it.
Stefan
^ permalink raw reply [flat|nested] 34+ messages in thread
* [Qemu-devel] [PATCH v5 05/11] dataplane: add event loop
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
` (3 preceding siblings ...)
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 04/11] dataplane: add virtqueue vring code Stefan Hajnoczi
@ 2012-12-05 20:47 ` Stefan Hajnoczi
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 06/11] dataplane: add Linux AIO request queue Stefan Hajnoczi
` (7 subsequent siblings)
12 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-05 20:47 UTC (permalink / raw)
To: qemu-devel
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
Outside the safety of the global mutex we need to poll on file
descriptors. I found epoll(2) is a convenient way to do that, although
other options could replace this module in the future (such as an
AioContext-based loop or glib's GMainLoop).
One important feature of this small event loop implementation is that
the loop can be terminated in a thread-safe way. This allows QEMU to
stop the data plane thread cleanly.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/dataplane/Makefile.objs | 2 +-
hw/dataplane/event-poll.c | 109 +++++++++++++++++++++++++++++++++++++++++++++
hw/dataplane/event-poll.h | 40 +++++++++++++++++
3 files changed, 150 insertions(+), 1 deletion(-)
create mode 100644 hw/dataplane/event-poll.c
create mode 100644 hw/dataplane/event-poll.h
diff --git a/hw/dataplane/Makefile.objs b/hw/dataplane/Makefile.objs
index 34e6d57..e26bd7d 100644
--- a/hw/dataplane/Makefile.objs
+++ b/hw/dataplane/Makefile.objs
@@ -1,3 +1,3 @@
ifeq ($(CONFIG_VIRTIO), y)
-common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o
+common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o event-poll.o
endif
diff --git a/hw/dataplane/event-poll.c b/hw/dataplane/event-poll.c
new file mode 100644
index 0000000..4a53d48
--- /dev/null
+++ b/hw/dataplane/event-poll.c
@@ -0,0 +1,109 @@
+/*
+ * Event loop with file descriptor polling
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include <sys/epoll.h>
+#include "hw/dataplane/event-poll.h"
+
+/* Add an event notifier and its callback for polling */
+void event_poll_add(EventPoll *poll, EventHandler *handler,
+ EventNotifier *notifier, EventCallback *callback)
+{
+ struct epoll_event event = {
+ .events = EPOLLIN,
+ .data.ptr = handler,
+ };
+ handler->notifier = notifier;
+ handler->callback = callback;
+ if (epoll_ctl(poll->epoll_fd, EPOLL_CTL_ADD,
+ event_notifier_get_fd(notifier), &event) != 0) {
+ fprintf(stderr, "failed to add event handler to epoll: %m\n");
+ exit(1);
+ }
+}
+
+/* Event callback for stopping the event_poll_run() loop */
+static bool handle_stop(EventHandler *handler)
+{
+ return false; /* stop event loop */
+}
+
+void event_poll_init(EventPoll *poll)
+{
+ /* Create epoll file descriptor */
+ poll->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
+ if (poll->epoll_fd < 0) {
+ fprintf(stderr, "epoll_create1 failed: %m\n");
+ exit(1);
+ }
+
+ /* Set up stop notifier */
+ if (event_notifier_init(&poll->stop_notifier, 0) < 0) {
+ fprintf(stderr, "failed to init stop notifier\n");
+ exit(1);
+ }
+ event_poll_add(poll, &poll->stop_handler,
+ &poll->stop_notifier, handle_stop);
+}
+
+void event_poll_cleanup(EventPoll *poll)
+{
+ event_notifier_cleanup(&poll->stop_notifier);
+ close(poll->epoll_fd);
+ poll->epoll_fd = -1;
+}
+
+/* Block until the next event and invoke its callback
+ *
+ * Signals must be masked, EINTR should never happen. This is true for QEMU
+ * threads.
+ */
+static bool event_poll(EventPoll *poll)
+{
+ EventHandler *handler;
+ struct epoll_event event;
+ int nevents;
+
+ /* Wait for the next event. Only do one event per call to keep the
+ * function simple, this could be changed later. */
+ nevents = epoll_wait(poll->epoll_fd, &event, 1, -1);
+ if (unlikely(nevents != 1)) {
+ fprintf(stderr, "epoll_wait failed: %m\n");
+ exit(1); /* should never happen */
+ }
+
+ /* Find out which event handler has become active */
+ handler = event.data.ptr;
+
+ /* Clear the eventfd */
+ event_notifier_test_and_clear(handler->notifier);
+
+ /* Handle the event */
+ return handler->callback(handler);
+}
+
+void event_poll_run(EventPoll *poll)
+{
+ while (event_poll(poll)) {
+ /* do nothing */
+ }
+}
+
+/* Stop the event_poll_run() loop
+ *
+ * This function can be used from another thread.
+ */
+void event_poll_stop(EventPoll *poll)
+{
+ event_notifier_set(&poll->stop_notifier);
+}
diff --git a/hw/dataplane/event-poll.h b/hw/dataplane/event-poll.h
new file mode 100644
index 0000000..5e1771f
--- /dev/null
+++ b/hw/dataplane/event-poll.h
@@ -0,0 +1,40 @@
+/*
+ * Event loop with file descriptor polling
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef EVENT_POLL_H
+#define EVENT_POLL_H
+
+#include "event_notifier.h"
+
+typedef struct EventHandler EventHandler;
+typedef bool EventCallback(EventHandler *handler);
+struct EventHandler {
+ EventNotifier *notifier; /* eventfd */
+ EventCallback *callback; /* callback function */
+};
+
+typedef struct {
+ int epoll_fd; /* epoll(2) file descriptor */
+ EventNotifier stop_notifier; /* stop poll notifier */
+ EventHandler stop_handler; /* stop poll handler */
+} EventPoll;
+
+void event_poll_add(EventPoll *poll, EventHandler *handler,
+ EventNotifier *notifier, EventCallback *callback);
+void event_poll_init(EventPoll *poll);
+void event_poll_cleanup(EventPoll *poll);
+void event_poll_run(EventPoll *poll);
+void event_poll_stop(EventPoll *poll);
+
+#endif /* EVENT_POLL_H */
--
1.8.0.1
^ permalink raw reply related [flat|nested] 34+ messages in thread* [Qemu-devel] [PATCH v5 06/11] dataplane: add Linux AIO request queue
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
` (4 preceding siblings ...)
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 05/11] dataplane: add event loop Stefan Hajnoczi
@ 2012-12-05 20:47 ` Stefan Hajnoczi
2012-12-07 14:21 ` Kevin Wolf
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 07/11] iov: add iov_discard() to remove data Stefan Hajnoczi
` (6 subsequent siblings)
12 siblings, 1 reply; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-05 20:47 UTC (permalink / raw)
To: qemu-devel
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
The IOQueue has a pool of iocb structs and a function to add new
read/write requests. Multiple requests can be added before calling the
submit function to actually tell the host kernel to begin I/O. This
allows callers to batch requests and submit them in one go.
The actual I/O is performed using Linux AIO.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/dataplane/Makefile.objs | 2 +-
hw/dataplane/ioq.c | 118 +++++++++++++++++++++++++++++++++++++++++++++
hw/dataplane/ioq.h | 57 ++++++++++++++++++++++
3 files changed, 176 insertions(+), 1 deletion(-)
create mode 100644 hw/dataplane/ioq.c
create mode 100644 hw/dataplane/ioq.h
diff --git a/hw/dataplane/Makefile.objs b/hw/dataplane/Makefile.objs
index e26bd7d..abd408f 100644
--- a/hw/dataplane/Makefile.objs
+++ b/hw/dataplane/Makefile.objs
@@ -1,3 +1,3 @@
ifeq ($(CONFIG_VIRTIO), y)
-common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o event-poll.o
+common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o event-poll.o ioq.o
endif
diff --git a/hw/dataplane/ioq.c b/hw/dataplane/ioq.c
new file mode 100644
index 0000000..7adeb5d
--- /dev/null
+++ b/hw/dataplane/ioq.c
@@ -0,0 +1,118 @@
+/*
+ * Linux AIO request queue
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "hw/dataplane/ioq.h"
+
+void ioq_init(IOQueue *ioq, int fd, unsigned int max_reqs)
+{
+ int rc;
+
+ ioq->fd = fd;
+ ioq->max_reqs = max_reqs;
+
+ memset(&ioq->io_ctx, 0, sizeof ioq->io_ctx);
+ rc = io_setup(max_reqs, &ioq->io_ctx);
+ if (rc != 0) {
+ fprintf(stderr, "ioq io_setup failed %d\n", rc);
+ exit(1);
+ }
+
+ rc = event_notifier_init(&ioq->io_notifier, 0);
+ if (rc != 0) {
+ fprintf(stderr, "ioq io event notifier creation failed %d\n", rc);
+ exit(1);
+ }
+
+ ioq->freelist = g_malloc0(sizeof ioq->freelist[0] * max_reqs);
+ ioq->freelist_idx = 0;
+
+ ioq->queue = g_malloc0(sizeof ioq->queue[0] * max_reqs);
+ ioq->queue_idx = 0;
+}
+
+void ioq_cleanup(IOQueue *ioq)
+{
+ g_free(ioq->freelist);
+ g_free(ioq->queue);
+
+ event_notifier_cleanup(&ioq->io_notifier);
+ io_destroy(ioq->io_ctx);
+}
+
+EventNotifier *ioq_get_notifier(IOQueue *ioq)
+{
+ return &ioq->io_notifier;
+}
+
+struct iocb *ioq_get_iocb(IOQueue *ioq)
+{
+ if (unlikely(ioq->freelist_idx == 0)) {
+ fprintf(stderr, "ioq underflow\n");
+ exit(1);
+ }
+ struct iocb *iocb = ioq->freelist[--ioq->freelist_idx];
+ ioq->queue[ioq->queue_idx++] = iocb;
+ return iocb;
+}
+
+void ioq_put_iocb(IOQueue *ioq, struct iocb *iocb)
+{
+ if (unlikely(ioq->freelist_idx == ioq->max_reqs)) {
+ fprintf(stderr, "ioq overflow\n");
+ exit(1);
+ }
+ ioq->freelist[ioq->freelist_idx++] = iocb;
+}
+
+struct iocb *ioq_rdwr(IOQueue *ioq, bool read, struct iovec *iov,
+ unsigned int count, long long offset)
+{
+ struct iocb *iocb = ioq_get_iocb(ioq);
+
+ if (read) {
+ io_prep_preadv(iocb, ioq->fd, iov, count, offset);
+ } else {
+ io_prep_pwritev(iocb, ioq->fd, iov, count, offset);
+ }
+ io_set_eventfd(iocb, event_notifier_get_fd(&ioq->io_notifier));
+ return iocb;
+}
+
+int ioq_submit(IOQueue *ioq)
+{
+ int rc = io_submit(ioq->io_ctx, ioq->queue_idx, ioq->queue);
+ ioq->queue_idx = 0; /* reset */
+ return rc;
+}
+
+int ioq_run_completion(IOQueue *ioq, IOQueueCompletion *completion,
+ void *opaque)
+{
+ struct io_event events[ioq->max_reqs];
+ int nevents, i;
+
+ nevents = io_getevents(ioq->io_ctx, 0, ioq->max_reqs, events, NULL);
+ if (unlikely(nevents < 0)) {
+ fprintf(stderr, "io_getevents failed %d\n", nevents);
+ exit(1);
+ }
+
+ for (i = 0; i < nevents; i++) {
+ ssize_t ret = ((uint64_t)events[i].res2 << 32) | events[i].res;
+
+ completion(events[i].obj, ret, opaque);
+ ioq_put_iocb(ioq, events[i].obj);
+ }
+ return nevents;
+}
diff --git a/hw/dataplane/ioq.h b/hw/dataplane/ioq.h
new file mode 100644
index 0000000..890db22
--- /dev/null
+++ b/hw/dataplane/ioq.h
@@ -0,0 +1,57 @@
+/*
+ * Linux AIO request queue
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef IOQ_H
+#define IOQ_H
+
+#include <libaio.h>
+#include "event_notifier.h"
+
+typedef struct {
+ int fd; /* file descriptor */
+ unsigned int max_reqs; /* max length of freelist and queue */
+
+ io_context_t io_ctx; /* Linux AIO context */
+ EventNotifier io_notifier; /* Linux AIO eventfd */
+
+ /* Requests can complete in any order so a free list is necessary to manage
+ * available iocbs.
+ */
+ struct iocb **freelist; /* free iocbs */
+ unsigned int freelist_idx;
+
+ /* Multiple requests are queued up before submitting them all in one go */
+ struct iocb **queue; /* queued iocbs */
+ unsigned int queue_idx;
+} IOQueue;
+
+void ioq_init(IOQueue *ioq, int fd, unsigned int max_reqs);
+void ioq_cleanup(IOQueue *ioq);
+EventNotifier *ioq_get_notifier(IOQueue *ioq);
+struct iocb *ioq_get_iocb(IOQueue *ioq);
+void ioq_put_iocb(IOQueue *ioq, struct iocb *iocb);
+struct iocb *ioq_rdwr(IOQueue *ioq, bool read, struct iovec *iov,
+ unsigned int count, long long offset);
+int ioq_submit(IOQueue *ioq);
+
+static inline unsigned int ioq_num_queued(IOQueue *ioq)
+{
+ return ioq->queue_idx;
+}
+
+typedef void IOQueueCompletion(struct iocb *iocb, ssize_t ret, void *opaque);
+int ioq_run_completion(IOQueue *ioq, IOQueueCompletion *completion,
+ void *opaque);
+
+#endif /* IOQ_H */
--
1.8.0.1
^ permalink raw reply related [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 06/11] dataplane: add Linux AIO request queue
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 06/11] dataplane: add Linux AIO request queue Stefan Hajnoczi
@ 2012-12-07 14:21 ` Kevin Wolf
2012-12-10 13:05 ` Stefan Hajnoczi
0 siblings, 1 reply; 34+ messages in thread
From: Kevin Wolf @ 2012-12-07 14:21 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Anthony Liguori, Michael S. Tsirkin, qemu-devel, Blue Swirl, khoa,
Paolo Bonzini, asias
Am 05.12.2012 21:47, schrieb Stefan Hajnoczi:
> The IOQueue has a pool of iocb structs and a function to add new
> read/write requests. Multiple requests can be added before calling the
> submit function to actually tell the host kernel to begin I/O. This
> allows callers to batch requests and submit them in one go.
>
> The actual I/O is performed using Linux AIO.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> hw/dataplane/Makefile.objs | 2 +-
> hw/dataplane/ioq.c | 118 +++++++++++++++++++++++++++++++++++++++++++++
> hw/dataplane/ioq.h | 57 ++++++++++++++++++++++
> 3 files changed, 176 insertions(+), 1 deletion(-)
> create mode 100644 hw/dataplane/ioq.c
> create mode 100644 hw/dataplane/ioq.h
>
> diff --git a/hw/dataplane/Makefile.objs b/hw/dataplane/Makefile.objs
> index e26bd7d..abd408f 100644
> --- a/hw/dataplane/Makefile.objs
> +++ b/hw/dataplane/Makefile.objs
> @@ -1,3 +1,3 @@
> ifeq ($(CONFIG_VIRTIO), y)
> -common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o event-poll.o
> +common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o event-poll.o ioq.o
> endif
> diff --git a/hw/dataplane/ioq.c b/hw/dataplane/ioq.c
> new file mode 100644
> index 0000000..7adeb5d
> --- /dev/null
> +++ b/hw/dataplane/ioq.c
> @@ -0,0 +1,118 @@
> +/*
> + * Linux AIO request queue
> + *
> + * Copyright 2012 IBM, Corp.
> + * Copyright 2012 Red Hat, Inc. and/or its affiliates
> + *
> + * Authors:
> + * Stefan Hajnoczi <stefanha@redhat.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include "hw/dataplane/ioq.h"
> +
> +void ioq_init(IOQueue *ioq, int fd, unsigned int max_reqs)
> +{
> + int rc;
> +
> + ioq->fd = fd;
> + ioq->max_reqs = max_reqs;
> +
> + memset(&ioq->io_ctx, 0, sizeof ioq->io_ctx);
> + rc = io_setup(max_reqs, &ioq->io_ctx);
> + if (rc != 0) {
> + fprintf(stderr, "ioq io_setup failed %d\n", rc);
> + exit(1);
> + }
> +
> + rc = event_notifier_init(&ioq->io_notifier, 0);
> + if (rc != 0) {
> + fprintf(stderr, "ioq io event notifier creation failed %d\n", rc);
> + exit(1);
> + }
> +
> + ioq->freelist = g_malloc0(sizeof ioq->freelist[0] * max_reqs);
> + ioq->freelist_idx = 0;
> +
> + ioq->queue = g_malloc0(sizeof ioq->queue[0] * max_reqs);
> + ioq->queue_idx = 0;
> +}
> +
> +void ioq_cleanup(IOQueue *ioq)
> +{
> + g_free(ioq->freelist);
> + g_free(ioq->queue);
> +
> + event_notifier_cleanup(&ioq->io_notifier);
> + io_destroy(ioq->io_ctx);
> +}
> +
> +EventNotifier *ioq_get_notifier(IOQueue *ioq)
> +{
> + return &ioq->io_notifier;
> +}
> +
> +struct iocb *ioq_get_iocb(IOQueue *ioq)
> +{
> + if (unlikely(ioq->freelist_idx == 0)) {
> + fprintf(stderr, "ioq underflow\n");
> + exit(1);
> + }
Can this happen? If no, it should be an assertion. If yes, the error
handling code is wrong, we can't just exit qemu. It's already not nice
to do it in setup functions, but during runtime I think it's not acceptable.
> + struct iocb *iocb = ioq->freelist[--ioq->freelist_idx];
> + ioq->queue[ioq->queue_idx++] = iocb;
> + return iocb;
> +}
> +
> +void ioq_put_iocb(IOQueue *ioq, struct iocb *iocb)
> +{
> + if (unlikely(ioq->freelist_idx == ioq->max_reqs)) {
> + fprintf(stderr, "ioq overflow\n");
> + exit(1);
> + }
Same here.
Kevin
^ permalink raw reply [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 06/11] dataplane: add Linux AIO request queue
2012-12-07 14:21 ` Kevin Wolf
@ 2012-12-10 13:05 ` Stefan Hajnoczi
0 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-10 13:05 UTC (permalink / raw)
To: Kevin Wolf
Cc: Anthony Liguori, Michael S. Tsirkin, qemu-devel, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
On Fri, Dec 07, 2012 at 03:21:22PM +0100, Kevin Wolf wrote:
> Am 05.12.2012 21:47, schrieb Stefan Hajnoczi:
> > The IOQueue has a pool of iocb structs and a function to add new
> > read/write requests. Multiple requests can be added before calling the
> > submit function to actually tell the host kernel to begin I/O. This
> > allows callers to batch requests and submit them in one go.
> >
> > The actual I/O is performed using Linux AIO.
> >
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> > hw/dataplane/Makefile.objs | 2 +-
> > hw/dataplane/ioq.c | 118 +++++++++++++++++++++++++++++++++++++++++++++
> > hw/dataplane/ioq.h | 57 ++++++++++++++++++++++
> > 3 files changed, 176 insertions(+), 1 deletion(-)
> > create mode 100644 hw/dataplane/ioq.c
> > create mode 100644 hw/dataplane/ioq.h
> >
> > diff --git a/hw/dataplane/Makefile.objs b/hw/dataplane/Makefile.objs
> > index e26bd7d..abd408f 100644
> > --- a/hw/dataplane/Makefile.objs
> > +++ b/hw/dataplane/Makefile.objs
> > @@ -1,3 +1,3 @@
> > ifeq ($(CONFIG_VIRTIO), y)
> > -common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o event-poll.o
> > +common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o event-poll.o ioq.o
> > endif
> > diff --git a/hw/dataplane/ioq.c b/hw/dataplane/ioq.c
> > new file mode 100644
> > index 0000000..7adeb5d
> > --- /dev/null
> > +++ b/hw/dataplane/ioq.c
> > @@ -0,0 +1,118 @@
> > +/*
> > + * Linux AIO request queue
> > + *
> > + * Copyright 2012 IBM, Corp.
> > + * Copyright 2012 Red Hat, Inc. and/or its affiliates
> > + *
> > + * Authors:
> > + * Stefan Hajnoczi <stefanha@redhat.com>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> > + * See the COPYING file in the top-level directory.
> > + *
> > + */
> > +
> > +#include "hw/dataplane/ioq.h"
> > +
> > +void ioq_init(IOQueue *ioq, int fd, unsigned int max_reqs)
> > +{
> > + int rc;
> > +
> > + ioq->fd = fd;
> > + ioq->max_reqs = max_reqs;
> > +
> > + memset(&ioq->io_ctx, 0, sizeof ioq->io_ctx);
> > + rc = io_setup(max_reqs, &ioq->io_ctx);
> > + if (rc != 0) {
> > + fprintf(stderr, "ioq io_setup failed %d\n", rc);
> > + exit(1);
> > + }
> > +
> > + rc = event_notifier_init(&ioq->io_notifier, 0);
> > + if (rc != 0) {
> > + fprintf(stderr, "ioq io event notifier creation failed %d\n", rc);
> > + exit(1);
> > + }
> > +
> > + ioq->freelist = g_malloc0(sizeof ioq->freelist[0] * max_reqs);
> > + ioq->freelist_idx = 0;
> > +
> > + ioq->queue = g_malloc0(sizeof ioq->queue[0] * max_reqs);
> > + ioq->queue_idx = 0;
> > +}
> > +
> > +void ioq_cleanup(IOQueue *ioq)
> > +{
> > + g_free(ioq->freelist);
> > + g_free(ioq->queue);
> > +
> > + event_notifier_cleanup(&ioq->io_notifier);
> > + io_destroy(ioq->io_ctx);
> > +}
> > +
> > +EventNotifier *ioq_get_notifier(IOQueue *ioq)
> > +{
> > + return &ioq->io_notifier;
> > +}
> > +
> > +struct iocb *ioq_get_iocb(IOQueue *ioq)
> > +{
> > + if (unlikely(ioq->freelist_idx == 0)) {
> > + fprintf(stderr, "ioq underflow\n");
> > + exit(1);
> > + }
>
> Can this happen? If no, it should be an assertion. If yes, the error
> handling code is wrong, we can't just exit qemu. It's already not nice
> to do it in setup functions, but during runtime I think it's not acceptable.
>
> > + struct iocb *iocb = ioq->freelist[--ioq->freelist_idx];
> > + ioq->queue[ioq->queue_idx++] = iocb;
> > + return iocb;
> > +}
> > +
> > +void ioq_put_iocb(IOQueue *ioq, struct iocb *iocb)
> > +{
> > + if (unlikely(ioq->freelist_idx == ioq->max_reqs)) {
> > + fprintf(stderr, "ioq overflow\n");
> > + exit(1);
> > + }
>
> Same here.
The ioq is sized so that guest cannot submit more than max_reqs due to
vring size. Therefore this cannot happen and I have changed them to
asserts.
Stefan
^ permalink raw reply [flat|nested] 34+ messages in thread
* [Qemu-devel] [PATCH v5 07/11] iov: add iov_discard() to remove data
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
` (5 preceding siblings ...)
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 06/11] dataplane: add Linux AIO request queue Stefan Hajnoczi
@ 2012-12-05 20:47 ` Stefan Hajnoczi
2012-12-06 11:36 ` Michael S. Tsirkin
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 08/11] test-iov: add iov_discard() testcase Stefan Hajnoczi
` (5 subsequent siblings)
12 siblings, 1 reply; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-05 20:47 UTC (permalink / raw)
To: qemu-devel
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
The iov_discard() function removes data from the front or back of the
vector. This is useful when peeling off header/footer structs.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
iov.c | 41 +++++++++++++++++++++++++++++++++++++++++
iov.h | 13 +++++++++++++
2 files changed, 54 insertions(+)
diff --git a/iov.c b/iov.c
index a81eedc..6eed089 100644
--- a/iov.c
+++ b/iov.c
@@ -354,3 +354,44 @@ size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
{
return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
}
+
+size_t iov_discard(struct iovec **iov, unsigned int *iov_cnt, ssize_t bytes)
+{
+ size_t total = 0;
+ struct iovec *cur;
+ int direction;
+
+ if (*iov_cnt == 0) {
+ return 0;
+ }
+
+ if (bytes < 0) {
+ bytes = -bytes;
+ direction = -1;
+ cur = *iov + (*iov_cnt - 1);
+ } else {
+ direction = 1;
+ cur = *iov;
+ }
+
+ while (*iov_cnt > 0) {
+ if (cur->iov_len > bytes) {
+ if (direction > 0) {
+ cur->iov_base += bytes;
+ }
+ cur->iov_len -= bytes;
+ total += bytes;
+ break;
+ }
+
+ bytes -= cur->iov_len;
+ total += cur->iov_len;
+ cur += direction;
+ *iov_cnt -= 1;
+ }
+
+ if (direction > 0) {
+ *iov = cur;
+ }
+ return total;
+}
diff --git a/iov.h b/iov.h
index 34c8ec9..d6d1fa6 100644
--- a/iov.h
+++ b/iov.h
@@ -95,3 +95,16 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
const struct iovec *iov, unsigned int iov_cnt,
size_t offset, size_t bytes);
+
+/*
+ * Remove a given number of bytes from the front or back of a vector.
+ * This may update iov and/or iov_cnt to exclude iovec elements that are
+ * no longer required.
+ *
+ * Data is discarded from the front of the vector if bytes is positive and
+ * from the back of the vector if bytes is negative.
+ *
+ * The number of bytes actually discarded is returned. This number may be
+ * smaller than requested if the vector is too small.
+ */
+size_t iov_discard(struct iovec **iov, unsigned int *iov_cnt, ssize_t bytes);
--
1.8.0.1
^ permalink raw reply related [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 07/11] iov: add iov_discard() to remove data
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 07/11] iov: add iov_discard() to remove data Stefan Hajnoczi
@ 2012-12-06 11:36 ` Michael S. Tsirkin
2012-12-06 14:07 ` Stefan Hajnoczi
0 siblings, 1 reply; 34+ messages in thread
From: Michael S. Tsirkin @ 2012-12-06 11:36 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Kevin Wolf, Anthony Liguori, qemu-devel, Blue Swirl, khoa,
Paolo Bonzini, asias
On Wed, Dec 05, 2012 at 09:47:06PM +0100, Stefan Hajnoczi wrote:
> The iov_discard() function removes data from the front or back of the
> vector. This is useful when peeling off header/footer structs.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> iov.c | 41 +++++++++++++++++++++++++++++++++++++++++
> iov.h | 13 +++++++++++++
> 2 files changed, 54 insertions(+)
>
> diff --git a/iov.c b/iov.c
> index a81eedc..6eed089 100644
> --- a/iov.c
> +++ b/iov.c
> @@ -354,3 +354,44 @@ size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
> {
> return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
> }
> +
> +size_t iov_discard(struct iovec **iov, unsigned int *iov_cnt, ssize_t bytes)
> +{
> + size_t total = 0;
> + struct iovec *cur;
> + int direction;
> +
> + if (*iov_cnt == 0) {
> + return 0;
> + }
> +
> + if (bytes < 0) {
> + bytes = -bytes;
> + direction = -1;
> + cur = *iov + (*iov_cnt - 1);
> + } else {
> + direction = 1;
> + cur = *iov;
> + }
> +
> + while (*iov_cnt > 0) {
> + if (cur->iov_len > bytes) {
> + if (direction > 0) {
> + cur->iov_base += bytes;
> + }
> + cur->iov_len -= bytes;
> + total += bytes;
> + break;
> + }
> +
> + bytes -= cur->iov_len;
> + total += cur->iov_len;
> + cur += direction;
> + *iov_cnt -= 1;
> + }
> +
> + if (direction > 0) {
> + *iov = cur;
> + }
> + return total;
> +}
> diff --git a/iov.h b/iov.h
> index 34c8ec9..d6d1fa6 100644
> --- a/iov.h
> +++ b/iov.h
> @@ -95,3 +95,16 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
> unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
> const struct iovec *iov, unsigned int iov_cnt,
> size_t offset, size_t bytes);
> +
> +/*
> + * Remove a given number of bytes from the front or back of a vector.
> + * This may update iov and/or iov_cnt to exclude iovec elements that are
> + * no longer required.
> + *
> + * Data is discarded from the front of the vector if bytes is positive and
> + * from the back of the vector if bytes is negative.
I think I already commented on this: I think this interface is too tricky,
and use of ssize_t is a bad idea since most of code uses size_t:
you might start getting integer overflow errors if you convert.
Better to have
size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt, ssize_t bytes);
size_t iov_discard_back(struct iovec **iov, unsigned int *iov_cnt, ssize_t bytes);
which explicitly do the right thing.
The fix up users to use size_t everywhere.
> + *
> + * The number of bytes actually discarded is returned. This number may be
> + * smaller than requested if the vector is too small.
> + */
> +size_t iov_discard(struct iovec **iov, unsigned int *iov_cnt, ssize_t bytes);
> --
> 1.8.0.1
^ permalink raw reply [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 07/11] iov: add iov_discard() to remove data
2012-12-06 11:36 ` Michael S. Tsirkin
@ 2012-12-06 14:07 ` Stefan Hajnoczi
0 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-06 14:07 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Kevin Wolf, Anthony Liguori, qemu-devel, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
On Thu, Dec 06, 2012 at 01:36:42PM +0200, Michael S. Tsirkin wrote:
> On Wed, Dec 05, 2012 at 09:47:06PM +0100, Stefan Hajnoczi wrote:
> > The iov_discard() function removes data from the front or back of the
> > vector. This is useful when peeling off header/footer structs.
> >
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> > iov.c | 41 +++++++++++++++++++++++++++++++++++++++++
> > iov.h | 13 +++++++++++++
> > 2 files changed, 54 insertions(+)
> >
> > diff --git a/iov.c b/iov.c
> > index a81eedc..6eed089 100644
> > --- a/iov.c
> > +++ b/iov.c
> > @@ -354,3 +354,44 @@ size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
> > {
> > return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
> > }
> > +
> > +size_t iov_discard(struct iovec **iov, unsigned int *iov_cnt, ssize_t bytes)
> > +{
> > + size_t total = 0;
> > + struct iovec *cur;
> > + int direction;
> > +
> > + if (*iov_cnt == 0) {
> > + return 0;
> > + }
> > +
> > + if (bytes < 0) {
> > + bytes = -bytes;
> > + direction = -1;
> > + cur = *iov + (*iov_cnt - 1);
> > + } else {
> > + direction = 1;
> > + cur = *iov;
> > + }
> > +
> > + while (*iov_cnt > 0) {
> > + if (cur->iov_len > bytes) {
> > + if (direction > 0) {
> > + cur->iov_base += bytes;
> > + }
> > + cur->iov_len -= bytes;
> > + total += bytes;
> > + break;
> > + }
> > +
> > + bytes -= cur->iov_len;
> > + total += cur->iov_len;
> > + cur += direction;
> > + *iov_cnt -= 1;
> > + }
> > +
> > + if (direction > 0) {
> > + *iov = cur;
> > + }
> > + return total;
> > +}
> > diff --git a/iov.h b/iov.h
> > index 34c8ec9..d6d1fa6 100644
> > --- a/iov.h
> > +++ b/iov.h
> > @@ -95,3 +95,16 @@ void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
> > unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
> > const struct iovec *iov, unsigned int iov_cnt,
> > size_t offset, size_t bytes);
> > +
> > +/*
> > + * Remove a given number of bytes from the front or back of a vector.
> > + * This may update iov and/or iov_cnt to exclude iovec elements that are
> > + * no longer required.
> > + *
> > + * Data is discarded from the front of the vector if bytes is positive and
> > + * from the back of the vector if bytes is negative.
>
> I think I already commented on this: I think this interface is too tricky,
> and use of ssize_t is a bad idea since most of code uses size_t:
> you might start getting integer overflow errors if you convert.
>
> Better to have
> size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt, ssize_t bytes);
> size_t iov_discard_back(struct iovec **iov, unsigned int *iov_cnt, ssize_t bytes);
>
> which explicitly do the right thing.
>
> The fix up users to use size_t everywhere.
Okay, will split into front/back.
Stefan
^ permalink raw reply [flat|nested] 34+ messages in thread
* [Qemu-devel] [PATCH v5 08/11] test-iov: add iov_discard() testcase
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
` (6 preceding siblings ...)
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 07/11] iov: add iov_discard() to remove data Stefan Hajnoczi
@ 2012-12-05 20:47 ` Stefan Hajnoczi
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 09/11] iov: add qemu_iovec_concat_iov() Stefan Hajnoczi
` (4 subsequent siblings)
12 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-05 20:47 UTC (permalink / raw)
To: qemu-devel
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
tests/test-iov.c | 129 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 129 insertions(+)
diff --git a/tests/test-iov.c b/tests/test-iov.c
index cbe7a89..7997fb5 100644
--- a/tests/test-iov.c
+++ b/tests/test-iov.c
@@ -250,11 +250,140 @@ static void test_io(void)
#endif
}
+static void test_discard(void)
+{
+ struct iovec *iov;
+ struct iovec *iov_tmp;
+ unsigned int iov_cnt;
+ unsigned int iov_cnt_tmp;
+ void *old_base;
+ size_t size;
+ size_t ret;
+
+ /* Discard zero bytes */
+ iov_random(&iov, &iov_cnt);
+ iov_tmp = iov;
+ iov_cnt_tmp = iov_cnt;
+ ret = iov_discard(&iov_tmp, &iov_cnt_tmp, 0);
+ g_assert(ret == 0);
+ g_assert(iov_tmp == iov);
+ g_assert(iov_cnt_tmp == iov_cnt);
+ iov_free(iov, iov_cnt);
+
+ /* Discard more bytes than vector size */
+ iov_random(&iov, &iov_cnt);
+ iov_tmp = iov;
+ iov_cnt_tmp = iov_cnt;
+ size = iov_size(iov, iov_cnt);
+ ret = iov_discard(&iov_tmp, &iov_cnt_tmp, size + 1);
+ g_assert(ret == size);
+ g_assert(iov_cnt_tmp == 0);
+ iov_free(iov, iov_cnt);
+
+ /* Discard more bytes than vector size (negative) */
+ iov_random(&iov, &iov_cnt);
+ iov_tmp = iov;
+ iov_cnt_tmp = iov_cnt;
+ size = iov_size(iov, iov_cnt);
+ ret = iov_discard(&iov_tmp, &iov_cnt_tmp, -(size + 1));
+ g_assert(ret == size);
+ g_assert(iov_cnt_tmp == 0);
+ iov_free(iov, iov_cnt);
+
+ /* Discard entire vector */
+ iov_random(&iov, &iov_cnt);
+ iov_tmp = iov;
+ iov_cnt_tmp = iov_cnt;
+ size = iov_size(iov, iov_cnt);
+ ret = iov_discard(&iov_tmp, &iov_cnt_tmp, size);
+ g_assert(ret == size);
+ g_assert(iov_cnt_tmp == 0);
+ iov_free(iov, iov_cnt);
+
+ /* Discard within first element */
+ iov_random(&iov, &iov_cnt);
+ iov_tmp = iov;
+ iov_cnt_tmp = iov_cnt;
+ old_base = iov->iov_base;
+ size = g_test_rand_int_range(1, iov->iov_len);
+ ret = iov_discard(&iov_tmp, &iov_cnt_tmp, size);
+ g_assert(ret == size);
+ g_assert(iov_tmp == iov);
+ g_assert(iov_cnt_tmp == iov_cnt);
+ g_assert(iov_tmp->iov_base == old_base + size);
+ iov_tmp->iov_base = old_base; /* undo before g_free() */
+ iov_free(iov, iov_cnt);
+
+ /* Discard entire first element */
+ iov_random(&iov, &iov_cnt);
+ iov_tmp = iov;
+ iov_cnt_tmp = iov_cnt;
+ ret = iov_discard(&iov_tmp, &iov_cnt_tmp, iov->iov_len);
+ g_assert(ret == iov->iov_len);
+ g_assert(iov_tmp == iov + 1);
+ g_assert(iov_cnt_tmp == iov_cnt - 1);
+ iov_free(iov, iov_cnt);
+
+ /* Discard within second element */
+ iov_random(&iov, &iov_cnt);
+ iov_tmp = iov;
+ iov_cnt_tmp = iov_cnt;
+ old_base = iov[1].iov_base;
+ size = iov->iov_len + g_test_rand_int_range(1, iov[1].iov_len);
+ ret = iov_discard(&iov_tmp, &iov_cnt_tmp, size);
+ g_assert(ret == size);
+ g_assert(iov_tmp == iov + 1);
+ g_assert(iov_cnt_tmp == iov_cnt - 1);
+ g_assert(iov_tmp->iov_base == old_base + (size - iov->iov_len));
+ iov_tmp->iov_base = old_base; /* undo before g_free() */
+ iov_free(iov, iov_cnt);
+
+ /* Discard within last element */
+ iov_random(&iov, &iov_cnt);
+ iov_tmp = iov;
+ iov_cnt_tmp = iov_cnt;
+ old_base = iov[iov_cnt - 1].iov_base;
+ size = g_test_rand_int_range(1, iov[iov_cnt - 1].iov_len);
+ ret = iov_discard(&iov_tmp, &iov_cnt_tmp, -size);
+ g_assert(ret == size);
+ g_assert(iov_tmp == iov);
+ g_assert(iov_cnt_tmp == iov_cnt);
+ g_assert(iov[iov_cnt - 1].iov_base == old_base);
+ iov_free(iov, iov_cnt);
+
+ /* Discard entire last element */
+ iov_random(&iov, &iov_cnt);
+ iov_tmp = iov;
+ iov_cnt_tmp = iov_cnt;
+ old_base = iov[iov_cnt - 1].iov_base;
+ size = iov[iov_cnt - 1].iov_len;
+ ret = iov_discard(&iov_tmp, &iov_cnt_tmp, -size);
+ g_assert(ret == size);
+ g_assert(iov_tmp == iov);
+ g_assert(iov_cnt_tmp == iov_cnt - 1);
+ iov_free(iov, iov_cnt);
+
+ /* Discard within second-to-last element */
+ iov_random(&iov, &iov_cnt);
+ iov_tmp = iov;
+ iov_cnt_tmp = iov_cnt;
+ old_base = iov[iov_cnt - 2].iov_base;
+ size = iov[iov_cnt - 1].iov_len +
+ g_test_rand_int_range(1, iov[iov_cnt - 2].iov_len);
+ ret = iov_discard(&iov_tmp, &iov_cnt_tmp, -size);
+ g_assert(ret == size);
+ g_assert(iov_tmp == iov);
+ g_assert(iov_cnt_tmp == iov_cnt - 1);
+ g_assert(iov[iov_cnt - 2].iov_base == old_base);
+ iov_free(iov, iov_cnt);
+}
+
int main(int argc, char **argv)
{
g_test_init(&argc, &argv, NULL);
g_test_rand_int();
g_test_add_func("/basic/iov/from-to-buf", test_to_from_buf);
g_test_add_func("/basic/iov/io", test_io);
+ g_test_add_func("/basic/iov/discard", test_discard);
return g_test_run();
}
--
1.8.0.1
^ permalink raw reply related [flat|nested] 34+ messages in thread* [Qemu-devel] [PATCH v5 09/11] iov: add qemu_iovec_concat_iov()
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
` (7 preceding siblings ...)
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 08/11] test-iov: add iov_discard() testcase Stefan Hajnoczi
@ 2012-12-05 20:47 ` Stefan Hajnoczi
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code Stefan Hajnoczi
` (3 subsequent siblings)
12 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-05 20:47 UTC (permalink / raw)
To: qemu-devel
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
The qemu_iovec_concat() function copies a subset of a QEMUIOVector. The
new qemu_iovec_concat_iov() function does the same for a iov/cnt pair.
It is easy to define qemu_iovec_concat() in terms of
qemu_iovec_concat_iov(). The existing code is mostly unchanged, except
for the assertion src->size >= soffset, which cannot be efficiently
checked upfront on a iov/cnt pair. Instead we assert upon hitting the
end of src with an unsatisfied soffset.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
iov.c | 39 +++++++++++++++++++++++++++------------
qemu-common.h | 3 +++
2 files changed, 30 insertions(+), 12 deletions(-)
diff --git a/iov.c b/iov.c
index 6eed089..1d4c5fe 100644
--- a/iov.c
+++ b/iov.c
@@ -289,34 +289,49 @@ void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
}
/*
- * Concatenates (partial) iovecs from src to the end of dst.
+ * Concatenates (partial) iovecs from src_iov to the end of dst.
* It starts copying after skipping `soffset' bytes at the
* beginning of src and adds individual vectors from src to
* dst copies up to `sbytes' bytes total, or up to the end
- * of src if it comes first. This way, it is okay to specify
+ * of src_iov if it comes first. This way, it is okay to specify
* very large value for `sbytes' to indicate "up to the end
* of src".
* Only vector pointers are processed, not the actual data buffers.
*/
-void qemu_iovec_concat(QEMUIOVector *dst,
- QEMUIOVector *src, size_t soffset, size_t sbytes)
+void qemu_iovec_concat_iov(QEMUIOVector *dst,
+ struct iovec *src_iov, unsigned int src_cnt,
+ size_t soffset, size_t sbytes)
{
int i;
size_t done;
- struct iovec *siov = src->iov;
assert(dst->nalloc != -1);
- assert(src->size >= soffset);
- for (i = 0, done = 0; done < sbytes && i < src->niov; i++) {
- if (soffset < siov[i].iov_len) {
- size_t len = MIN(siov[i].iov_len - soffset, sbytes - done);
- qemu_iovec_add(dst, siov[i].iov_base + soffset, len);
+ for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) {
+ if (soffset < src_iov[i].iov_len) {
+ size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done);
+ qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len);
done += len;
soffset = 0;
} else {
- soffset -= siov[i].iov_len;
+ soffset -= src_iov[i].iov_len;
}
}
- /* return done; */
+ assert(soffset == 0); /* offset beyond end of src */
+}
+
+/*
+ * Concatenates (partial) iovecs from src to the end of dst.
+ * It starts copying after skipping `soffset' bytes at the
+ * beginning of src and adds individual vectors from src to
+ * dst copies up to `sbytes' bytes total, or up to the end
+ * of src if it comes first. This way, it is okay to specify
+ * very large value for `sbytes' to indicate "up to the end
+ * of src".
+ * Only vector pointers are processed, not the actual data buffers.
+ */
+void qemu_iovec_concat(QEMUIOVector *dst,
+ QEMUIOVector *src, size_t soffset, size_t sbytes)
+{
+ qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);
}
void qemu_iovec_destroy(QEMUIOVector *qiov)
diff --git a/qemu-common.h b/qemu-common.h
index cef264c..4cc63e1 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -379,6 +379,9 @@ void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov);
void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len);
void qemu_iovec_concat(QEMUIOVector *dst,
QEMUIOVector *src, size_t soffset, size_t sbytes);
+void qemu_iovec_concat_iov(QEMUIOVector *dst,
+ struct iovec *src_iov, unsigned int src_cnt,
+ size_t soffset, size_t sbytes);
void qemu_iovec_destroy(QEMUIOVector *qiov);
void qemu_iovec_reset(QEMUIOVector *qiov);
size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
--
1.8.0.1
^ permalink raw reply related [flat|nested] 34+ messages in thread* [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
` (8 preceding siblings ...)
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 09/11] iov: add qemu_iovec_concat_iov() Stefan Hajnoczi
@ 2012-12-05 20:47 ` Stefan Hajnoczi
2012-12-06 7:35 ` Paolo Bonzini
` (2 more replies)
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 11/11] virtio-blk: add x-data-plane=on|off performance feature Stefan Hajnoczi
` (2 subsequent siblings)
12 siblings, 3 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-05 20:47 UTC (permalink / raw)
To: qemu-devel
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
virtio-blk-data-plane is a subset implementation of virtio-blk. It only
handles read, write, and flush requests. It does this using a dedicated
thread that executes an epoll(2)-based event loop and processes I/O
using Linux AIO.
This approach performs very well but can be used for raw image files
only. The number of IOPS achieved has been reported to be several times
higher than the existing virtio-blk implementation.
Eventually it should be possible to unify virtio-blk-data-plane with the
main body of QEMU code once the block layer and hardware emulation is
able to run outside the global mutex.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/dataplane/Makefile.objs | 2 +-
hw/dataplane/virtio-blk.c | 463 +++++++++++++++++++++++++++++++++++++++++++++
hw/dataplane/virtio-blk.h | 43 +++++
trace-events | 6 +
4 files changed, 513 insertions(+), 1 deletion(-)
create mode 100644 hw/dataplane/virtio-blk.c
create mode 100644 hw/dataplane/virtio-blk.h
diff --git a/hw/dataplane/Makefile.objs b/hw/dataplane/Makefile.objs
index abd408f..682aa9e 100644
--- a/hw/dataplane/Makefile.objs
+++ b/hw/dataplane/Makefile.objs
@@ -1,3 +1,3 @@
ifeq ($(CONFIG_VIRTIO), y)
-common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o event-poll.o ioq.o
+common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o event-poll.o ioq.o virtio-blk.o
endif
diff --git a/hw/dataplane/virtio-blk.c b/hw/dataplane/virtio-blk.c
new file mode 100644
index 0000000..64ea98e
--- /dev/null
+++ b/hw/dataplane/virtio-blk.c
@@ -0,0 +1,463 @@
+/*
+ * Dedicated thread for virtio-blk I/O processing
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "trace.h"
+#include "iov.h"
+#include "event-poll.h"
+#include "qemu-thread.h"
+#include "vring.h"
+#include "ioq.h"
+#include "migration.h"
+#include "hw/virtio-blk.h"
+#include "hw/dataplane/virtio-blk.h"
+
+enum {
+ SEG_MAX = 126, /* maximum number of I/O segments */
+ VRING_MAX = SEG_MAX + 2, /* maximum number of vring descriptors */
+ REQ_MAX = VRING_MAX, /* maximum number of requests in the vring,
+ * is VRING_MAX / 2 with traditional and
+ * VRING_MAX with indirect descriptors */
+};
+
+typedef struct {
+ struct iocb iocb; /* Linux AIO control block */
+ QEMUIOVector *inhdr; /* iovecs for virtio_blk_inhdr */
+ unsigned int head; /* vring descriptor index */
+} VirtIOBlockRequest;
+
+struct VirtIOBlockDataPlane {
+ bool started;
+ QEMUBH *start_bh;
+ QemuThread thread;
+
+ BlockDriverState *bs;
+ int fd; /* image file descriptor */
+
+ VirtIODevice *vdev;
+ Vring vring; /* virtqueue vring */
+ EventNotifier *guest_notifier; /* irq */
+
+ EventPoll event_poll; /* event poller */
+ EventHandler io_handler; /* Linux AIO completion handler */
+ EventHandler notify_handler; /* virtqueue notify handler */
+
+ IOQueue ioqueue; /* Linux AIO queue (should really be per
+ dataplane thread) */
+ VirtIOBlockRequest requests[REQ_MAX]; /* pool of requests, managed by the
+ queue */
+
+ unsigned int num_reqs;
+ QemuMutex num_reqs_lock;
+ QemuCond no_reqs_cond;
+
+ Error *migration_blocker;
+};
+
+/* Raise an interrupt to signal guest, if necessary */
+static void notify_guest(VirtIOBlockDataPlane *s)
+{
+ if (!vring_should_notify(s->vdev, &s->vring)) {
+ return;
+ }
+
+ event_notifier_set(s->guest_notifier);
+}
+
+static void complete_request(struct iocb *iocb, ssize_t ret, void *opaque)
+{
+ VirtIOBlockDataPlane *s = opaque;
+ VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb);
+ struct virtio_blk_inhdr hdr;
+ int len;
+
+ if (likely(ret >= 0)) {
+ hdr.status = VIRTIO_BLK_S_OK;
+ len = ret;
+ } else {
+ hdr.status = VIRTIO_BLK_S_IOERR;
+ len = 0;
+ }
+
+ trace_virtio_blk_data_plane_complete_request(s, req->head, ret);
+
+ qemu_iovec_from_buf(req->inhdr, 0, &hdr, sizeof(hdr));
+ qemu_iovec_destroy(req->inhdr);
+ g_slice_free(QEMUIOVector, req->inhdr);
+
+ /* According to the virtio specification len should be the number of bytes
+ * written to, but for virtio-blk it seems to be the number of bytes
+ * transferred plus the status bytes.
+ */
+ vring_push(&s->vring, req->head, len + sizeof(hdr));
+
+ qemu_mutex_lock(&s->num_reqs_lock);
+ if (--s->num_reqs == 0) {
+ qemu_cond_broadcast(&s->no_reqs_cond);
+ }
+ qemu_mutex_unlock(&s->num_reqs_lock);
+}
+
+static void fail_request_early(VirtIOBlockDataPlane *s, unsigned int head,
+ QEMUIOVector *inhdr, unsigned char status)
+{
+ struct virtio_blk_inhdr hdr = {
+ .status = status,
+ };
+
+ qemu_iovec_from_buf(inhdr, 0, &hdr, sizeof(hdr));
+ qemu_iovec_destroy(inhdr);
+ g_slice_free(QEMUIOVector, inhdr);
+
+ vring_push(&s->vring, head, sizeof(hdr));
+ notify_guest(s);
+}
+
+static int process_request(IOQueue *ioq, struct iovec iov[],
+ unsigned int out_num, unsigned int in_num,
+ unsigned int head)
+{
+ VirtIOBlockDataPlane *s = container_of(ioq, VirtIOBlockDataPlane, ioqueue);
+ struct iovec *in_iov = &iov[out_num];
+ struct virtio_blk_outhdr outhdr;
+ QEMUIOVector *inhdr;
+ size_t in_size;
+
+ /* Copy in outhdr */
+ if (unlikely(iov_to_buf(iov, out_num, 0, &outhdr,
+ sizeof(outhdr)) != sizeof(outhdr))) {
+ error_report("virtio-blk request outhdr too short");
+ return -EFAULT;
+ }
+ iov_discard(&iov, &out_num, sizeof(outhdr));
+
+ /* Grab inhdr for later */
+ in_size = iov_size(in_iov, in_num);
+ if (in_size < sizeof(struct virtio_blk_inhdr)) {
+ error_report("virtio_blk request inhdr too short");
+ return -EFAULT;
+ }
+ inhdr = g_slice_new(QEMUIOVector);
+ qemu_iovec_init(inhdr, 1);
+ qemu_iovec_concat_iov(inhdr, in_iov, in_num,
+ in_size - sizeof(struct virtio_blk_inhdr),
+ sizeof(struct virtio_blk_inhdr));
+ iov_discard(&in_iov, &in_num, -sizeof(struct virtio_blk_inhdr));
+
+ /* TODO Linux sets the barrier bit even when not advertised! */
+ outhdr.type &= ~VIRTIO_BLK_T_BARRIER;
+
+ struct iocb *iocb;
+ switch (outhdr.type & (VIRTIO_BLK_T_OUT | VIRTIO_BLK_T_SCSI_CMD |
+ VIRTIO_BLK_T_FLUSH)) {
+ case VIRTIO_BLK_T_IN:
+ iocb = ioq_rdwr(ioq, true, in_iov, in_num, outhdr.sector * 512);
+ break;
+
+ case VIRTIO_BLK_T_OUT:
+ iocb = ioq_rdwr(ioq, false, iov, out_num, outhdr.sector * 512);
+ break;
+
+ case VIRTIO_BLK_T_SCSI_CMD:
+ /* TODO support SCSI commands */
+ fail_request_early(s, head, inhdr, VIRTIO_BLK_S_UNSUPP);
+ return 0;
+
+ case VIRTIO_BLK_T_FLUSH:
+ /* TODO fdsync not supported by Linux AIO, do it synchronously here! */
+ fdatasync(s->fd);
+ fail_request_early(s, head, inhdr, VIRTIO_BLK_S_OK);
+ return 0;
+
+ default:
+ error_report("virtio-blk unsupported request type %#x", outhdr.type);
+ qemu_iovec_destroy(inhdr);
+ g_slice_free(QEMUIOVector, inhdr);
+ return -EFAULT;
+ }
+
+ /* Fill in virtio block metadata needed for completion */
+ VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb);
+ req->head = head;
+ req->inhdr = inhdr;
+ return 0;
+}
+
+static bool handle_notify(EventHandler *handler)
+{
+ VirtIOBlockDataPlane *s = container_of(handler, VirtIOBlockDataPlane,
+ notify_handler);
+
+ /* There is one array of iovecs into which all new requests are extracted
+ * from the vring. Requests are read from the vring and the translated
+ * descriptors are written to the iovecs array. The iovecs do not have to
+ * persist across handle_notify() calls because the kernel copies the
+ * iovecs on io_submit().
+ *
+ * Handling io_submit() EAGAIN may require storing the requests across
+ * handle_notify() calls until the kernel has sufficient resources to
+ * accept more I/O. This is not implemented yet.
+ */
+ struct iovec iovec[VRING_MAX];
+ struct iovec *end = &iovec[VRING_MAX];
+ struct iovec *iov = iovec;
+
+ /* When a request is read from the vring, the index of the first descriptor
+ * (aka head) is returned so that the completed request can be pushed onto
+ * the vring later.
+ *
+ * The number of hypervisor read-only iovecs is out_num. The number of
+ * hypervisor write-only iovecs is in_num.
+ */
+ int head;
+ unsigned int out_num = 0, in_num = 0;
+ unsigned int num_queued;
+
+ for (;;) {
+ /* Disable guest->host notifies to avoid unnecessary vmexits */
+ vring_disable_notification(s->vdev, &s->vring);
+
+ for (;;) {
+ head = vring_pop(s->vdev, &s->vring, iov, end, &out_num, &in_num);
+ if (head < 0) {
+ break; /* no more requests */
+ }
+
+ trace_virtio_blk_data_plane_process_request(s, out_num, in_num,
+ head);
+
+ if (process_request(&s->ioqueue, iov, out_num, in_num, head) < 0) {
+ vring_set_broken(&s->vring);
+ break;
+ }
+ iov += out_num + in_num;
+ }
+
+ if (likely(head == -EAGAIN)) { /* vring emptied */
+ /* Re-enable guest->host notifies and stop processing the vring.
+ * But if the guest has snuck in more descriptors, keep processing.
+ */
+ if (vring_enable_notification(s->vdev, &s->vring)) {
+ break;
+ }
+ } else { /* head == -ENOBUFS or fatal error, iovecs[] is depleted */
+ /* Since there are no iovecs[] left, stop processing for now. Do
+ * not re-enable guest->host notifies since the I/O completion
+ * handler knows to check for more vring descriptors anyway.
+ */
+ break;
+ }
+ }
+
+ num_queued = ioq_num_queued(&s->ioqueue);
+ if (num_queued > 0) {
+ qemu_mutex_lock(&s->num_reqs_lock);
+ s->num_reqs += num_queued;
+ qemu_mutex_unlock(&s->num_reqs_lock);
+
+ int rc = ioq_submit(&s->ioqueue);
+ if (unlikely(rc < 0)) {
+ fprintf(stderr, "ioq_submit failed %d\n", rc);
+ exit(1);
+ }
+ }
+ return true;
+}
+
+static bool handle_io(EventHandler *handler)
+{
+ VirtIOBlockDataPlane *s = container_of(handler, VirtIOBlockDataPlane,
+ io_handler);
+
+ if (ioq_run_completion(&s->ioqueue, complete_request, s) > 0) {
+ notify_guest(s);
+ }
+
+ /* If there were more requests than iovecs, the vring will not be empty yet
+ * so check again. There should now be enough resources to process more
+ * requests.
+ */
+ if (unlikely(vring_more_avail(&s->vring))) {
+ return handle_notify(&s->notify_handler);
+ }
+
+ return true;
+}
+
+static void *data_plane_thread(void *opaque)
+{
+ VirtIOBlockDataPlane *s = opaque;
+ event_poll_run(&s->event_poll);
+ return NULL;
+}
+
+static void start_data_plane_bh(void *opaque)
+{
+ VirtIOBlockDataPlane *s = opaque;
+
+ qemu_bh_delete(s->start_bh);
+ s->start_bh = NULL;
+ qemu_thread_create(&s->thread, data_plane_thread,
+ s, QEMU_THREAD_JOINABLE);
+}
+
+bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
+ VirtIOBlockDataPlane **dataplane)
+{
+ VirtIOBlockDataPlane *s;
+ int fd;
+
+ *dataplane = NULL;
+
+ if (!blk->data_plane) {
+ return true;
+ }
+
+ if (blk->scsi) {
+ error_report("device is incompatible with x-data-plane, use scsi=off");
+ return false;
+ }
+
+ fd = raw_get_aio_fd(blk->conf.bs);
+ if (fd < 0) {
+ error_report("drive is incompatible with x-data-plane, "
+ "use format=raw,cache=none,aio=native");
+ return false;
+ }
+
+ s = g_new0(VirtIOBlockDataPlane, 1);
+ s->vdev = vdev;
+ s->fd = fd;
+ s->bs = blk->conf.bs;
+
+ /* Prevent block operations that conflict with data plane thread */
+ bdrv_set_in_use(s->bs, 1);
+
+ error_setg(&s->migration_blocker,
+ "x-data-plane does not support migration");
+ migrate_add_blocker(s->migration_blocker);
+
+ *dataplane = s;
+ return true;
+}
+
+void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
+{
+ if (!s) {
+ return;
+ }
+
+ virtio_blk_data_plane_stop(s);
+ migrate_del_blocker(s->migration_blocker);
+ error_free(s->migration_blocker);
+ bdrv_set_in_use(s->bs, 0);
+ g_free(s);
+}
+
+/* Block until pending requests have completed
+ *
+ * The vring continues to be serviced so ensure no new requests will be added
+ * to avoid races.
+ */
+void virtio_blk_data_plane_drain(VirtIOBlockDataPlane *s)
+{
+ qemu_mutex_lock(&s->num_reqs_lock);
+ while (s->num_reqs > 0) {
+ qemu_cond_wait(&s->no_reqs_cond, &s->num_reqs_lock);
+ }
+ qemu_mutex_unlock(&s->num_reqs_lock);
+}
+
+void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
+{
+ VirtQueue *vq;
+ int i;
+
+ if (s->started) {
+ return;
+ }
+
+ vq = virtio_get_queue(s->vdev, 0);
+ if (!vring_setup(&s->vring, s->vdev, 0)) {
+ return;
+ }
+
+ event_poll_init(&s->event_poll);
+
+ /* Set up guest notifier (irq) */
+ if (s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque,
+ true) != 0) {
+ fprintf(stderr, "virtio-blk failed to set guest notifier, "
+ "ensure -enable-kvm is set\n");
+ exit(1);
+ }
+ s->guest_notifier = virtio_queue_get_guest_notifier(vq);
+
+ /* Set up virtqueue notify */
+ if (s->vdev->binding->set_host_notifier(s->vdev->binding_opaque,
+ 0, true) != 0) {
+ fprintf(stderr, "virtio-blk failed to set host notifier\n");
+ exit(1);
+ }
+ event_poll_add(&s->event_poll, &s->notify_handler,
+ virtio_queue_get_host_notifier(vq),
+ handle_notify);
+
+ /* Set up ioqueue */
+ ioq_init(&s->ioqueue, s->fd, REQ_MAX);
+ for (i = 0; i < ARRAY_SIZE(s->requests); i++) {
+ ioq_put_iocb(&s->ioqueue, &s->requests[i].iocb);
+ }
+ event_poll_add(&s->event_poll, &s->io_handler,
+ ioq_get_notifier(&s->ioqueue), handle_io);
+
+ s->started = true;
+ trace_virtio_blk_data_plane_start(s);
+
+ /* Kick right away to begin processing requests already in vring */
+ event_notifier_set(virtio_queue_get_host_notifier(vq));
+
+ /* Spawn thread in BH so it inherits iothread cpusets */
+ s->start_bh = qemu_bh_new(start_data_plane_bh, s);
+ qemu_bh_schedule(s->start_bh);
+}
+
+void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
+{
+ if (!s->started) {
+ return;
+ }
+ s->started = false;
+ trace_virtio_blk_data_plane_stop(s);
+
+ /* Stop thread or cancel pending thread creation BH */
+ if (s->start_bh) {
+ qemu_bh_delete(s->start_bh);
+ s->start_bh = NULL;
+ } else {
+ virtio_blk_data_plane_drain(s);
+ event_poll_stop(&s->event_poll);
+ qemu_thread_join(&s->thread);
+ }
+
+ ioq_cleanup(&s->ioqueue);
+
+ s->vdev->binding->set_host_notifier(s->vdev->binding_opaque, 0, false);
+
+ event_poll_cleanup(&s->event_poll);
+
+ /* Clean up guest notifier (irq) */
+ s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque, false);
+
+ vring_teardown(&s->vring);
+}
diff --git a/hw/dataplane/virtio-blk.h b/hw/dataplane/virtio-blk.h
new file mode 100644
index 0000000..a0dd89b
--- /dev/null
+++ b/hw/dataplane/virtio-blk.h
@@ -0,0 +1,43 @@
+/*
+ * Dedicated thread for virtio-blk I/O processing
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Stefan Hajnoczi <stefanha@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef HW_DATAPLANE_VIRTIO_BLK_H
+#define HW_DATAPLANE_VIRTIO_BLK_H
+
+#include "hw/virtio.h"
+
+typedef struct VirtIOBlockDataPlane VirtIOBlockDataPlane;
+
+#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
+bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
+ VirtIOBlockDataPlane **dataplane);
+void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s);
+void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s);
+void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s);
+void virtio_blk_data_plane_drain(VirtIOBlockDataPlane *s);
+#else
+static inline bool virtio_blk_data_plane_create(VirtIODevice *vdev,
+ VirtIOBlkConf *blk, VirtIOBlockDataPlane **dataplane)
+{
+ *dataplane = NULL;
+ return true;
+}
+
+static inline void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s) {}
+static inline void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s) {}
+static inline void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s) {}
+static inline void virtio_blk_data_plane_drain(VirtIOBlockDataPlane *s) {}
+#endif
+
+#endif /* HW_DATAPLANE_VIRTIO_BLK_H */
diff --git a/trace-events b/trace-events
index a9a791b..1edc2ae 100644
--- a/trace-events
+++ b/trace-events
@@ -98,6 +98,12 @@ virtio_blk_rw_complete(void *req, int ret) "req %p ret %d"
virtio_blk_handle_write(void *req, uint64_t sector, size_t nsectors) "req %p sector %"PRIu64" nsectors %zu"
virtio_blk_handle_read(void *req, uint64_t sector, size_t nsectors) "req %p sector %"PRIu64" nsectors %zu"
+# hw/dataplane/virtio-blk.c
+virtio_blk_data_plane_start(void *s) "dataplane %p"
+virtio_blk_data_plane_stop(void *s) "dataplane %p"
+virtio_blk_data_plane_process_request(void *s, unsigned int out_num, unsigned int in_num, unsigned int head) "dataplane %p out_num %u in_num %u head %u"
+virtio_blk_data_plane_complete_request(void *s, unsigned int head, int ret) "dataplane %p head %u ret %d"
+
# hw/dataplane/vring.c
vring_setup(uint64_t physical, void *desc, void *avail, void *used) "vring physical %#"PRIx64" desc %p avail %p used %p"
--
1.8.0.1
^ permalink raw reply related [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code Stefan Hajnoczi
@ 2012-12-06 7:35 ` Paolo Bonzini
2012-12-06 14:03 ` Stefan Hajnoczi
2012-12-07 6:06 ` Stefan Hajnoczi
2012-12-06 11:33 ` Michael S. Tsirkin
2012-12-07 18:04 ` Kevin Wolf
2 siblings, 2 replies; 34+ messages in thread
From: Paolo Bonzini @ 2012-12-06 7:35 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, qemu-devel,
Blue Swirl, khoa, asias
Il 05/12/2012 21:47, Stefan Hajnoczi ha scritto:
> +
> +/* Block until pending requests have completed
> + *
> + * The vring continues to be serviced so ensure no new requests will be added
> + * to avoid races.
> + */
> +void virtio_blk_data_plane_drain(VirtIOBlockDataPlane *s)
> +{
> + qemu_mutex_lock(&s->num_reqs_lock);
> + while (s->num_reqs > 0) {
> + qemu_cond_wait(&s->no_reqs_cond, &s->num_reqs_lock);
> + }
> + qemu_mutex_unlock(&s->num_reqs_lock);
> +}
Hi Stefan,
so this was not changed from v4?
Paolo
^ permalink raw reply [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code
2012-12-06 7:35 ` Paolo Bonzini
@ 2012-12-06 14:03 ` Stefan Hajnoczi
2012-12-07 6:06 ` Stefan Hajnoczi
1 sibling, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-06 14:03 UTC (permalink / raw)
To: Paolo Bonzini
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, qemu-devel,
Blue Swirl, khoa, asias
On Thu, Dec 06, 2012 at 08:35:55AM +0100, Paolo Bonzini wrote:
> Il 05/12/2012 21:47, Stefan Hajnoczi ha scritto:
> > +
> > +/* Block until pending requests have completed
> > + *
> > + * The vring continues to be serviced so ensure no new requests will be added
> > + * to avoid races.
> > + */
> > +void virtio_blk_data_plane_drain(VirtIOBlockDataPlane *s)
> > +{
> > + qemu_mutex_lock(&s->num_reqs_lock);
> > + while (s->num_reqs > 0) {
> > + qemu_cond_wait(&s->no_reqs_cond, &s->num_reqs_lock);
> > + }
> > + qemu_mutex_unlock(&s->num_reqs_lock);
> > +}
>
> Hi Stefan,
>
> so this was not changed from v4?
It's unchanged. From the v5 cover letter:
* Note I did not get rid of the mutex+condvar approach to draining
requests. I've had good feedback on the performance of the patch
series so I'm not worried about eliminating the lock (it's very
rarely contended). Hope Michael and Paolo are okay with this
approach.
Stefan
^ permalink raw reply [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code
2012-12-06 7:35 ` Paolo Bonzini
2012-12-06 14:03 ` Stefan Hajnoczi
@ 2012-12-07 6:06 ` Stefan Hajnoczi
2012-12-07 10:51 ` Paolo Bonzini
1 sibling, 1 reply; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-07 6:06 UTC (permalink / raw)
To: Paolo Bonzini
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, qemu-devel,
Blue Swirl, khoa, asias
On Thu, Dec 06, 2012 at 08:35:55AM +0100, Paolo Bonzini wrote:
> Il 05/12/2012 21:47, Stefan Hajnoczi ha scritto:
> > +
> > +/* Block until pending requests have completed
> > + *
> > + * The vring continues to be serviced so ensure no new requests will be added
> > + * to avoid races.
> > + */
> > +void virtio_blk_data_plane_drain(VirtIOBlockDataPlane *s)
> > +{
> > + qemu_mutex_lock(&s->num_reqs_lock);
> > + while (s->num_reqs > 0) {
> > + qemu_cond_wait(&s->no_reqs_cond, &s->num_reqs_lock);
> > + }
> > + qemu_mutex_unlock(&s->num_reqs_lock);
> > +}
>
> Hi Stefan,
>
> so this was not changed from v4?
BTW I should go into slightly more detail about why I stopped short of
implementing the notify+join approach.
notify+join means stopping the event loop and data plane thread so
that the caller is sure that virtio-blk-data-plane is quiesced.
Unfortunately this doesn't map nicely to bdrv_drain_all() where the
caller has the global mutex, quiesces I/O, and then performs a critical
operation. I/O resumes after the caller returns or releases the global
mutex:
bdrv_drain_all();
critical_operation();
return;
/* now it's okay to process I/O again */
We cannot use notify+join here because bdrv_drain_all() would stop the
data plane thread but nothing restarts it!
Perhaps we'd need a "resume" call after the critical operation so that
the data plane thread is restarted - but this sounds invasive and is a
departure from how existing I/O and emulated devices work.
Stefan
^ permalink raw reply [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code
2012-12-07 6:06 ` Stefan Hajnoczi
@ 2012-12-07 10:51 ` Paolo Bonzini
0 siblings, 0 replies; 34+ messages in thread
From: Paolo Bonzini @ 2012-12-07 10:51 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, qemu-devel,
Blue Swirl, khoa, asias
Il 07/12/2012 07:06, Stefan Hajnoczi ha scritto:
> BTW I should go into slightly more detail about why I stopped short of
> implementing the notify+join approach.
>
> notify+join means stopping the event loop and data plane thread so
> that the caller is sure that virtio-blk-data-plane is quiesced.
>
> Unfortunately this doesn't map nicely to bdrv_drain_all() where the
> caller has the global mutex, quiesces I/O, and then performs a critical
> operation. I/O resumes after the caller returns or releases the global
> mutex:
>
> bdrv_drain_all();
> critical_operation();
> return;
> /* now it's okay to process I/O again */
>
> We cannot use notify+join here because bdrv_drain_all() would stop the
> data plane thread but nothing restarts it!
That's true. The solution here for AioContext would be to run the event
loop in the context of the thread that is calling bdrv_drain_all(). But
you do not need bdrv_drain_all() right now, and the event loop would be
rewritten anyway to use AioContext, so the lack of "resume" is not a
problem for now IMHO.
> Perhaps we'd need a "resume" call after the critical operation so that
> the data plane thread is restarted - but this sounds invasive and is a
> departure from how existing I/O and emulated devices work.
The problem was more about the possible race in the draining of
requests, but it's okay to tackle it later.
Paolo
^ permalink raw reply [flat|nested] 34+ messages in thread
* Re: [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code Stefan Hajnoczi
2012-12-06 7:35 ` Paolo Bonzini
@ 2012-12-06 11:33 ` Michael S. Tsirkin
2012-12-07 5:43 ` Stefan Hajnoczi
2012-12-07 18:04 ` Kevin Wolf
2 siblings, 1 reply; 34+ messages in thread
From: Michael S. Tsirkin @ 2012-12-06 11:33 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Kevin Wolf, Anthony Liguori, qemu-devel, Blue Swirl, khoa,
Paolo Bonzini, asias
On Wed, Dec 05, 2012 at 09:47:09PM +0100, Stefan Hajnoczi wrote:
> virtio-blk-data-plane is a subset implementation of virtio-blk.
I already asked this:
what confuses me a bit is how, being a subset, it exposes the
same feature bits. For example wce config is ineffective, right?
So I think it should not expose WCE feature bit.
> It only
> handles read, write, and flush requests. It does this using a dedicated
> thread that executes an epoll(2)-based event loop and processes I/O
> using Linux AIO.
>
> This approach performs very well but can be used for raw image files
> only. The number of IOPS achieved has been reported to be several times
> higher than the existing virtio-blk implementation.
>
> Eventually it should be possible to unify virtio-blk-data-plane with the
> main body of QEMU code once the block layer and hardware emulation is
> able to run outside the global mutex.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> hw/dataplane/Makefile.objs | 2 +-
> hw/dataplane/virtio-blk.c | 463 +++++++++++++++++++++++++++++++++++++++++++++
> hw/dataplane/virtio-blk.h | 43 +++++
> trace-events | 6 +
> 4 files changed, 513 insertions(+), 1 deletion(-)
> create mode 100644 hw/dataplane/virtio-blk.c
> create mode 100644 hw/dataplane/virtio-blk.h
>
> diff --git a/hw/dataplane/Makefile.objs b/hw/dataplane/Makefile.objs
> index abd408f..682aa9e 100644
> --- a/hw/dataplane/Makefile.objs
> +++ b/hw/dataplane/Makefile.objs
> @@ -1,3 +1,3 @@
> ifeq ($(CONFIG_VIRTIO), y)
> -common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o event-poll.o ioq.o
> +common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o event-poll.o ioq.o virtio-blk.o
> endif
> diff --git a/hw/dataplane/virtio-blk.c b/hw/dataplane/virtio-blk.c
> new file mode 100644
> index 0000000..64ea98e
> --- /dev/null
> +++ b/hw/dataplane/virtio-blk.c
> @@ -0,0 +1,463 @@
> +/*
> + * Dedicated thread for virtio-blk I/O processing
> + *
> + * Copyright 2012 IBM, Corp.
> + * Copyright 2012 Red Hat, Inc. and/or its affiliates
> + *
> + * Authors:
> + * Stefan Hajnoczi <stefanha@redhat.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include "trace.h"
> +#include "iov.h"
> +#include "event-poll.h"
> +#include "qemu-thread.h"
> +#include "vring.h"
> +#include "ioq.h"
> +#include "migration.h"
> +#include "hw/virtio-blk.h"
> +#include "hw/dataplane/virtio-blk.h"
> +
> +enum {
> + SEG_MAX = 126, /* maximum number of I/O segments */
> + VRING_MAX = SEG_MAX + 2, /* maximum number of vring descriptors */
> + REQ_MAX = VRING_MAX, /* maximum number of requests in the vring,
> + * is VRING_MAX / 2 with traditional and
> + * VRING_MAX with indirect descriptors */
> +};
> +
> +typedef struct {
> + struct iocb iocb; /* Linux AIO control block */
> + QEMUIOVector *inhdr; /* iovecs for virtio_blk_inhdr */
> + unsigned int head; /* vring descriptor index */
> +} VirtIOBlockRequest;
> +
> +struct VirtIOBlockDataPlane {
> + bool started;
> + QEMUBH *start_bh;
> + QemuThread thread;
> +
> + BlockDriverState *bs;
> + int fd; /* image file descriptor */
> +
> + VirtIODevice *vdev;
> + Vring vring; /* virtqueue vring */
> + EventNotifier *guest_notifier; /* irq */
> +
> + EventPoll event_poll; /* event poller */
> + EventHandler io_handler; /* Linux AIO completion handler */
> + EventHandler notify_handler; /* virtqueue notify handler */
> +
> + IOQueue ioqueue; /* Linux AIO queue (should really be per
> + dataplane thread) */
> + VirtIOBlockRequest requests[REQ_MAX]; /* pool of requests, managed by the
> + queue */
> +
> + unsigned int num_reqs;
> + QemuMutex num_reqs_lock;
> + QemuCond no_reqs_cond;
> +
> + Error *migration_blocker;
> +};
> +
> +/* Raise an interrupt to signal guest, if necessary */
> +static void notify_guest(VirtIOBlockDataPlane *s)
> +{
> + if (!vring_should_notify(s->vdev, &s->vring)) {
> + return;
> + }
> +
> + event_notifier_set(s->guest_notifier);
> +}
> +
> +static void complete_request(struct iocb *iocb, ssize_t ret, void *opaque)
> +{
> + VirtIOBlockDataPlane *s = opaque;
> + VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb);
> + struct virtio_blk_inhdr hdr;
> + int len;
> +
> + if (likely(ret >= 0)) {
> + hdr.status = VIRTIO_BLK_S_OK;
> + len = ret;
> + } else {
> + hdr.status = VIRTIO_BLK_S_IOERR;
> + len = 0;
> + }
> +
> + trace_virtio_blk_data_plane_complete_request(s, req->head, ret);
> +
> + qemu_iovec_from_buf(req->inhdr, 0, &hdr, sizeof(hdr));
> + qemu_iovec_destroy(req->inhdr);
> + g_slice_free(QEMUIOVector, req->inhdr);
> +
> + /* According to the virtio specification len should be the number of bytes
> + * written to, but for virtio-blk it seems to be the number of bytes
> + * transferred plus the status bytes.
> + */
> + vring_push(&s->vring, req->head, len + sizeof(hdr));
> +
> + qemu_mutex_lock(&s->num_reqs_lock);
> + if (--s->num_reqs == 0) {
> + qemu_cond_broadcast(&s->no_reqs_cond);
> + }
> + qemu_mutex_unlock(&s->num_reqs_lock);
> +}
> +
> +static void fail_request_early(VirtIOBlockDataPlane *s, unsigned int head,
> + QEMUIOVector *inhdr, unsigned char status)
> +{
> + struct virtio_blk_inhdr hdr = {
> + .status = status,
> + };
> +
> + qemu_iovec_from_buf(inhdr, 0, &hdr, sizeof(hdr));
> + qemu_iovec_destroy(inhdr);
> + g_slice_free(QEMUIOVector, inhdr);
> +
> + vring_push(&s->vring, head, sizeof(hdr));
> + notify_guest(s);
> +}
> +
> +static int process_request(IOQueue *ioq, struct iovec iov[],
> + unsigned int out_num, unsigned int in_num,
> + unsigned int head)
> +{
> + VirtIOBlockDataPlane *s = container_of(ioq, VirtIOBlockDataPlane, ioqueue);
> + struct iovec *in_iov = &iov[out_num];
> + struct virtio_blk_outhdr outhdr;
> + QEMUIOVector *inhdr;
> + size_t in_size;
> +
> + /* Copy in outhdr */
> + if (unlikely(iov_to_buf(iov, out_num, 0, &outhdr,
> + sizeof(outhdr)) != sizeof(outhdr))) {
> + error_report("virtio-blk request outhdr too short");
> + return -EFAULT;
> + }
> + iov_discard(&iov, &out_num, sizeof(outhdr));
> +
> + /* Grab inhdr for later */
> + in_size = iov_size(in_iov, in_num);
> + if (in_size < sizeof(struct virtio_blk_inhdr)) {
> + error_report("virtio_blk request inhdr too short");
> + return -EFAULT;
> + }
> + inhdr = g_slice_new(QEMUIOVector);
> + qemu_iovec_init(inhdr, 1);
> + qemu_iovec_concat_iov(inhdr, in_iov, in_num,
> + in_size - sizeof(struct virtio_blk_inhdr),
> + sizeof(struct virtio_blk_inhdr));
> + iov_discard(&in_iov, &in_num, -sizeof(struct virtio_blk_inhdr));
> +
> + /* TODO Linux sets the barrier bit even when not advertised! */
> + outhdr.type &= ~VIRTIO_BLK_T_BARRIER;
> +
> + struct iocb *iocb;
> + switch (outhdr.type & (VIRTIO_BLK_T_OUT | VIRTIO_BLK_T_SCSI_CMD |
> + VIRTIO_BLK_T_FLUSH)) {
> + case VIRTIO_BLK_T_IN:
> + iocb = ioq_rdwr(ioq, true, in_iov, in_num, outhdr.sector * 512);
> + break;
> +
> + case VIRTIO_BLK_T_OUT:
> + iocb = ioq_rdwr(ioq, false, iov, out_num, outhdr.sector * 512);
> + break;
> +
> + case VIRTIO_BLK_T_SCSI_CMD:
> + /* TODO support SCSI commands */
> + fail_request_early(s, head, inhdr, VIRTIO_BLK_S_UNSUPP);
> + return 0;
> +
> + case VIRTIO_BLK_T_FLUSH:
> + /* TODO fdsync not supported by Linux AIO, do it synchronously here! */
> + fdatasync(s->fd);
> + fail_request_early(s, head, inhdr, VIRTIO_BLK_S_OK);
> + return 0;
> +
> + default:
> + error_report("virtio-blk unsupported request type %#x", outhdr.type);
> + qemu_iovec_destroy(inhdr);
> + g_slice_free(QEMUIOVector, inhdr);
> + return -EFAULT;
> + }
> +
> + /* Fill in virtio block metadata needed for completion */
> + VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb);
> + req->head = head;
> + req->inhdr = inhdr;
> + return 0;
> +}
> +
> +static bool handle_notify(EventHandler *handler)
> +{
> + VirtIOBlockDataPlane *s = container_of(handler, VirtIOBlockDataPlane,
> + notify_handler);
> +
> + /* There is one array of iovecs into which all new requests are extracted
> + * from the vring. Requests are read from the vring and the translated
> + * descriptors are written to the iovecs array. The iovecs do not have to
> + * persist across handle_notify() calls because the kernel copies the
> + * iovecs on io_submit().
> + *
> + * Handling io_submit() EAGAIN may require storing the requests across
> + * handle_notify() calls until the kernel has sufficient resources to
> + * accept more I/O. This is not implemented yet.
> + */
> + struct iovec iovec[VRING_MAX];
> + struct iovec *end = &iovec[VRING_MAX];
> + struct iovec *iov = iovec;
> +
> + /* When a request is read from the vring, the index of the first descriptor
> + * (aka head) is returned so that the completed request can be pushed onto
> + * the vring later.
> + *
> + * The number of hypervisor read-only iovecs is out_num. The number of
> + * hypervisor write-only iovecs is in_num.
> + */
> + int head;
> + unsigned int out_num = 0, in_num = 0;
> + unsigned int num_queued;
> +
> + for (;;) {
> + /* Disable guest->host notifies to avoid unnecessary vmexits */
> + vring_disable_notification(s->vdev, &s->vring);
> +
> + for (;;) {
> + head = vring_pop(s->vdev, &s->vring, iov, end, &out_num, &in_num);
> + if (head < 0) {
> + break; /* no more requests */
> + }
> +
> + trace_virtio_blk_data_plane_process_request(s, out_num, in_num,
> + head);
> +
> + if (process_request(&s->ioqueue, iov, out_num, in_num, head) < 0) {
> + vring_set_broken(&s->vring);
> + break;
> + }
> + iov += out_num + in_num;
> + }
> +
> + if (likely(head == -EAGAIN)) { /* vring emptied */
> + /* Re-enable guest->host notifies and stop processing the vring.
> + * But if the guest has snuck in more descriptors, keep processing.
> + */
> + if (vring_enable_notification(s->vdev, &s->vring)) {
> + break;
> + }
> + } else { /* head == -ENOBUFS or fatal error, iovecs[] is depleted */
> + /* Since there are no iovecs[] left, stop processing for now. Do
> + * not re-enable guest->host notifies since the I/O completion
> + * handler knows to check for more vring descriptors anyway.
> + */
> + break;
> + }
> + }
> +
> + num_queued = ioq_num_queued(&s->ioqueue);
> + if (num_queued > 0) {
> + qemu_mutex_lock(&s->num_reqs_lock);
> + s->num_reqs += num_queued;
> + qemu_mutex_unlock(&s->num_reqs_lock);
> +
> + int rc = ioq_submit(&s->ioqueue);
> + if (unlikely(rc < 0)) {
> + fprintf(stderr, "ioq_submit failed %d\n", rc);
> + exit(1);
> + }
> + }
> + return true;
> +}
> +
> +static bool handle_io(EventHandler *handler)
> +{
> + VirtIOBlockDataPlane *s = container_of(handler, VirtIOBlockDataPlane,
> + io_handler);
> +
> + if (ioq_run_completion(&s->ioqueue, complete_request, s) > 0) {
> + notify_guest(s);
> + }
> +
> + /* If there were more requests than iovecs, the vring will not be empty yet
> + * so check again. There should now be enough resources to process more
> + * requests.
> + */
> + if (unlikely(vring_more_avail(&s->vring))) {
> + return handle_notify(&s->notify_handler);
> + }
> +
> + return true;
> +}
> +
> +static void *data_plane_thread(void *opaque)
> +{
> + VirtIOBlockDataPlane *s = opaque;
> + event_poll_run(&s->event_poll);
> + return NULL;
> +}
> +
> +static void start_data_plane_bh(void *opaque)
> +{
> + VirtIOBlockDataPlane *s = opaque;
> +
> + qemu_bh_delete(s->start_bh);
> + s->start_bh = NULL;
> + qemu_thread_create(&s->thread, data_plane_thread,
> + s, QEMU_THREAD_JOINABLE);
> +}
> +
> +bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
> + VirtIOBlockDataPlane **dataplane)
> +{
> + VirtIOBlockDataPlane *s;
> + int fd;
> +
> + *dataplane = NULL;
> +
> + if (!blk->data_plane) {
> + return true;
> + }
> +
> + if (blk->scsi) {
> + error_report("device is incompatible with x-data-plane, use scsi=off");
> + return false;
> + }
> +
> + fd = raw_get_aio_fd(blk->conf.bs);
> + if (fd < 0) {
> + error_report("drive is incompatible with x-data-plane, "
> + "use format=raw,cache=none,aio=native");
> + return false;
> + }
> +
> + s = g_new0(VirtIOBlockDataPlane, 1);
> + s->vdev = vdev;
> + s->fd = fd;
> + s->bs = blk->conf.bs;
> +
> + /* Prevent block operations that conflict with data plane thread */
> + bdrv_set_in_use(s->bs, 1);
> +
> + error_setg(&s->migration_blocker,
> + "x-data-plane does not support migration");
> + migrate_add_blocker(s->migration_blocker);
> +
> + *dataplane = s;
> + return true;
> +}
> +
> +void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
> +{
> + if (!s) {
> + return;
> + }
> +
> + virtio_blk_data_plane_stop(s);
> + migrate_del_blocker(s->migration_blocker);
> + error_free(s->migration_blocker);
> + bdrv_set_in_use(s->bs, 0);
> + g_free(s);
> +}
> +
> +/* Block until pending requests have completed
> + *
> + * The vring continues to be serviced so ensure no new requests will be added
> + * to avoid races.
> + */
> +void virtio_blk_data_plane_drain(VirtIOBlockDataPlane *s)
> +{
> + qemu_mutex_lock(&s->num_reqs_lock);
> + while (s->num_reqs > 0) {
> + qemu_cond_wait(&s->no_reqs_cond, &s->num_reqs_lock);
> + }
> + qemu_mutex_unlock(&s->num_reqs_lock);
> +}
> +
> +void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
> +{
> + VirtQueue *vq;
> + int i;
> +
> + if (s->started) {
> + return;
> + }
> +
> + vq = virtio_get_queue(s->vdev, 0);
> + if (!vring_setup(&s->vring, s->vdev, 0)) {
> + return;
> + }
> +
> + event_poll_init(&s->event_poll);
> +
> + /* Set up guest notifier (irq) */
> + if (s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque,
> + true) != 0) {
> + fprintf(stderr, "virtio-blk failed to set guest notifier, "
> + "ensure -enable-kvm is set\n");
> + exit(1);
> + }
> + s->guest_notifier = virtio_queue_get_guest_notifier(vq);
> +
> + /* Set up virtqueue notify */
> + if (s->vdev->binding->set_host_notifier(s->vdev->binding_opaque,
> + 0, true) != 0) {
> + fprintf(stderr, "virtio-blk failed to set host notifier\n");
> + exit(1);
> + }
> + event_poll_add(&s->event_poll, &s->notify_handler,
> + virtio_queue_get_host_notifier(vq),
> + handle_notify);
> +
> + /* Set up ioqueue */
> + ioq_init(&s->ioqueue, s->fd, REQ_MAX);
> + for (i = 0; i < ARRAY_SIZE(s->requests); i++) {
> + ioq_put_iocb(&s->ioqueue, &s->requests[i].iocb);
> + }
> + event_poll_add(&s->event_poll, &s->io_handler,
> + ioq_get_notifier(&s->ioqueue), handle_io);
> +
> + s->started = true;
> + trace_virtio_blk_data_plane_start(s);
> +
> + /* Kick right away to begin processing requests already in vring */
> + event_notifier_set(virtio_queue_get_host_notifier(vq));
> +
> + /* Spawn thread in BH so it inherits iothread cpusets */
> + s->start_bh = qemu_bh_new(start_data_plane_bh, s);
> + qemu_bh_schedule(s->start_bh);
> +}
> +
> +void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
> +{
> + if (!s->started) {
> + return;
> + }
> + s->started = false;
> + trace_virtio_blk_data_plane_stop(s);
> +
> + /* Stop thread or cancel pending thread creation BH */
> + if (s->start_bh) {
> + qemu_bh_delete(s->start_bh);
> + s->start_bh = NULL;
> + } else {
> + virtio_blk_data_plane_drain(s);
> + event_poll_stop(&s->event_poll);
> + qemu_thread_join(&s->thread);
> + }
> +
> + ioq_cleanup(&s->ioqueue);
> +
> + s->vdev->binding->set_host_notifier(s->vdev->binding_opaque, 0, false);
> +
> + event_poll_cleanup(&s->event_poll);
> +
> + /* Clean up guest notifier (irq) */
> + s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque, false);
> +
> + vring_teardown(&s->vring);
> +}
> diff --git a/hw/dataplane/virtio-blk.h b/hw/dataplane/virtio-blk.h
> new file mode 100644
> index 0000000..a0dd89b
> --- /dev/null
> +++ b/hw/dataplane/virtio-blk.h
> @@ -0,0 +1,43 @@
> +/*
> + * Dedicated thread for virtio-blk I/O processing
> + *
> + * Copyright 2012 IBM, Corp.
> + * Copyright 2012 Red Hat, Inc. and/or its affiliates
> + *
> + * Authors:
> + * Stefan Hajnoczi <stefanha@redhat.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#ifndef HW_DATAPLANE_VIRTIO_BLK_H
> +#define HW_DATAPLANE_VIRTIO_BLK_H
> +
> +#include "hw/virtio.h"
> +
> +typedef struct VirtIOBlockDataPlane VirtIOBlockDataPlane;
> +
> +#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
> +bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *blk,
> + VirtIOBlockDataPlane **dataplane);
> +void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s);
> +void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s);
> +void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s);
> +void virtio_blk_data_plane_drain(VirtIOBlockDataPlane *s);
> +#else
> +static inline bool virtio_blk_data_plane_create(VirtIODevice *vdev,
> + VirtIOBlkConf *blk, VirtIOBlockDataPlane **dataplane)
> +{
> + *dataplane = NULL;
> + return true;
> +}
> +
> +static inline void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s) {}
> +static inline void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s) {}
> +static inline void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s) {}
> +static inline void virtio_blk_data_plane_drain(VirtIOBlockDataPlane *s) {}
> +#endif
> +
> +#endif /* HW_DATAPLANE_VIRTIO_BLK_H */
> diff --git a/trace-events b/trace-events
> index a9a791b..1edc2ae 100644
> --- a/trace-events
> +++ b/trace-events
> @@ -98,6 +98,12 @@ virtio_blk_rw_complete(void *req, int ret) "req %p ret %d"
> virtio_blk_handle_write(void *req, uint64_t sector, size_t nsectors) "req %p sector %"PRIu64" nsectors %zu"
> virtio_blk_handle_read(void *req, uint64_t sector, size_t nsectors) "req %p sector %"PRIu64" nsectors %zu"
>
> +# hw/dataplane/virtio-blk.c
> +virtio_blk_data_plane_start(void *s) "dataplane %p"
> +virtio_blk_data_plane_stop(void *s) "dataplane %p"
> +virtio_blk_data_plane_process_request(void *s, unsigned int out_num, unsigned int in_num, unsigned int head) "dataplane %p out_num %u in_num %u head %u"
> +virtio_blk_data_plane_complete_request(void *s, unsigned int head, int ret) "dataplane %p head %u ret %d"
> +
> # hw/dataplane/vring.c
> vring_setup(uint64_t physical, void *desc, void *avail, void *used) "vring physical %#"PRIx64" desc %p avail %p used %p"
>
> --
> 1.8.0.1
^ permalink raw reply [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code
2012-12-06 11:33 ` Michael S. Tsirkin
@ 2012-12-07 5:43 ` Stefan Hajnoczi
0 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-07 5:43 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Kevin Wolf, Anthony Liguori, qemu-devel, Blue Swirl, khoa,
Paolo Bonzini, asias
On Thu, Dec 06, 2012 at 01:33:58PM +0200, Michael S. Tsirkin wrote:
> On Wed, Dec 05, 2012 at 09:47:09PM +0100, Stefan Hajnoczi wrote:
> > virtio-blk-data-plane is a subset implementation of virtio-blk.
>
> I already asked this:
>
> what confuses me a bit is how, being a subset, it exposes the
> same feature bits. For example wce config is ineffective, right?
> So I think it should not expose WCE feature bit.
It works like vhost - the virtio negotiation and setup is still handled
by QEMU but the actual vring processing is done by dataplane.
virtio-blk-data-plane works with cache=none. You're right that WCE
should not be toggled because we don't automatically flush after every
request.
Stefan
^ permalink raw reply [flat|nested] 34+ messages in thread
* Re: [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code Stefan Hajnoczi
2012-12-06 7:35 ` Paolo Bonzini
2012-12-06 11:33 ` Michael S. Tsirkin
@ 2012-12-07 18:04 ` Kevin Wolf
2012-12-10 13:06 ` Stefan Hajnoczi
2 siblings, 1 reply; 34+ messages in thread
From: Kevin Wolf @ 2012-12-07 18:04 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Anthony Liguori, Michael S. Tsirkin, qemu-devel, Blue Swirl, khoa,
Paolo Bonzini, asias
Am 05.12.2012 21:47, schrieb Stefan Hajnoczi:
> virtio-blk-data-plane is a subset implementation of virtio-blk. It only
> handles read, write, and flush requests. It does this using a dedicated
> thread that executes an epoll(2)-based event loop and processes I/O
> using Linux AIO.
>
> This approach performs very well but can be used for raw image files
> only. The number of IOPS achieved has been reported to be several times
> higher than the existing virtio-blk implementation.
>
> Eventually it should be possible to unify virtio-blk-data-plane with the
> main body of QEMU code once the block layer and hardware emulation is
> able to run outside the global mutex.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> +static int process_request(IOQueue *ioq, struct iovec iov[],
> + unsigned int out_num, unsigned int in_num,
> + unsigned int head)
> +{
> + VirtIOBlockDataPlane *s = container_of(ioq, VirtIOBlockDataPlane, ioqueue);
> + struct iovec *in_iov = &iov[out_num];
> + struct virtio_blk_outhdr outhdr;
> + QEMUIOVector *inhdr;
> + size_t in_size;
> +
> + /* Copy in outhdr */
> + if (unlikely(iov_to_buf(iov, out_num, 0, &outhdr,
> + sizeof(outhdr)) != sizeof(outhdr))) {
> + error_report("virtio-blk request outhdr too short");
> + return -EFAULT;
> + }
> + iov_discard(&iov, &out_num, sizeof(outhdr));
> +
> + /* Grab inhdr for later */
> + in_size = iov_size(in_iov, in_num);
> + if (in_size < sizeof(struct virtio_blk_inhdr)) {
> + error_report("virtio_blk request inhdr too short");
> + return -EFAULT;
> + }
> + inhdr = g_slice_new(QEMUIOVector);
> + qemu_iovec_init(inhdr, 1);
> + qemu_iovec_concat_iov(inhdr, in_iov, in_num,
> + in_size - sizeof(struct virtio_blk_inhdr),
> + sizeof(struct virtio_blk_inhdr));
> + iov_discard(&in_iov, &in_num, -sizeof(struct virtio_blk_inhdr));
> +
> + /* TODO Linux sets the barrier bit even when not advertised! */
> + outhdr.type &= ~VIRTIO_BLK_T_BARRIER;
> +
> + struct iocb *iocb;
> + switch (outhdr.type & (VIRTIO_BLK_T_OUT | VIRTIO_BLK_T_SCSI_CMD |
> + VIRTIO_BLK_T_FLUSH)) {
> + case VIRTIO_BLK_T_IN:
> + iocb = ioq_rdwr(ioq, true, in_iov, in_num, outhdr.sector * 512);
> + break;
> +
> + case VIRTIO_BLK_T_OUT:
> + iocb = ioq_rdwr(ioq, false, iov, out_num, outhdr.sector * 512);
> + break;
> +
> + case VIRTIO_BLK_T_SCSI_CMD:
> + /* TODO support SCSI commands */
> + fail_request_early(s, head, inhdr, VIRTIO_BLK_S_UNSUPP);
> + return 0;
> +
> + case VIRTIO_BLK_T_FLUSH:
> + /* TODO fdsync not supported by Linux AIO, do it synchronously here! */
> + fdatasync(s->fd);
We shouldn't ignore errors here.
> + fail_request_early(s, head, inhdr, VIRTIO_BLK_S_OK);
> + return 0;
> +
Kevin
^ permalink raw reply [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code
2012-12-07 18:04 ` Kevin Wolf
@ 2012-12-10 13:06 ` Stefan Hajnoczi
0 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-10 13:06 UTC (permalink / raw)
To: Kevin Wolf
Cc: Anthony Liguori, Michael S. Tsirkin, qemu-devel, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
On Fri, Dec 07, 2012 at 07:04:39PM +0100, Kevin Wolf wrote:
> Am 05.12.2012 21:47, schrieb Stefan Hajnoczi:
> > virtio-blk-data-plane is a subset implementation of virtio-blk. It only
> > handles read, write, and flush requests. It does this using a dedicated
> > thread that executes an epoll(2)-based event loop and processes I/O
> > using Linux AIO.
> >
> > This approach performs very well but can be used for raw image files
> > only. The number of IOPS achieved has been reported to be several times
> > higher than the existing virtio-blk implementation.
> >
> > Eventually it should be possible to unify virtio-blk-data-plane with the
> > main body of QEMU code once the block layer and hardware emulation is
> > able to run outside the global mutex.
> >
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
>
> > +static int process_request(IOQueue *ioq, struct iovec iov[],
> > + unsigned int out_num, unsigned int in_num,
> > + unsigned int head)
> > +{
> > + VirtIOBlockDataPlane *s = container_of(ioq, VirtIOBlockDataPlane, ioqueue);
> > + struct iovec *in_iov = &iov[out_num];
> > + struct virtio_blk_outhdr outhdr;
> > + QEMUIOVector *inhdr;
> > + size_t in_size;
> > +
> > + /* Copy in outhdr */
> > + if (unlikely(iov_to_buf(iov, out_num, 0, &outhdr,
> > + sizeof(outhdr)) != sizeof(outhdr))) {
> > + error_report("virtio-blk request outhdr too short");
> > + return -EFAULT;
> > + }
> > + iov_discard(&iov, &out_num, sizeof(outhdr));
> > +
> > + /* Grab inhdr for later */
> > + in_size = iov_size(in_iov, in_num);
> > + if (in_size < sizeof(struct virtio_blk_inhdr)) {
> > + error_report("virtio_blk request inhdr too short");
> > + return -EFAULT;
> > + }
> > + inhdr = g_slice_new(QEMUIOVector);
> > + qemu_iovec_init(inhdr, 1);
> > + qemu_iovec_concat_iov(inhdr, in_iov, in_num,
> > + in_size - sizeof(struct virtio_blk_inhdr),
> > + sizeof(struct virtio_blk_inhdr));
> > + iov_discard(&in_iov, &in_num, -sizeof(struct virtio_blk_inhdr));
> > +
> > + /* TODO Linux sets the barrier bit even when not advertised! */
> > + outhdr.type &= ~VIRTIO_BLK_T_BARRIER;
> > +
> > + struct iocb *iocb;
> > + switch (outhdr.type & (VIRTIO_BLK_T_OUT | VIRTIO_BLK_T_SCSI_CMD |
> > + VIRTIO_BLK_T_FLUSH)) {
> > + case VIRTIO_BLK_T_IN:
> > + iocb = ioq_rdwr(ioq, true, in_iov, in_num, outhdr.sector * 512);
> > + break;
> > +
> > + case VIRTIO_BLK_T_OUT:
> > + iocb = ioq_rdwr(ioq, false, iov, out_num, outhdr.sector * 512);
> > + break;
> > +
> > + case VIRTIO_BLK_T_SCSI_CMD:
> > + /* TODO support SCSI commands */
> > + fail_request_early(s, head, inhdr, VIRTIO_BLK_S_UNSUPP);
> > + return 0;
> > +
> > + case VIRTIO_BLK_T_FLUSH:
> > + /* TODO fdsync not supported by Linux AIO, do it synchronously here! */
> > + fdatasync(s->fd);
>
> We shouldn't ignore errors here.
Fixed, thanks.
Stefan
^ permalink raw reply [flat|nested] 34+ messages in thread
* [Qemu-devel] [PATCH v5 11/11] virtio-blk: add x-data-plane=on|off performance feature
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
` (9 preceding siblings ...)
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 10/11] dataplane: add virtio-blk data plane code Stefan Hajnoczi
@ 2012-12-05 20:47 ` Stefan Hajnoczi
2012-12-06 11:38 ` [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Michael S. Tsirkin
2012-12-07 2:43 ` Liu Yuan
12 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-05 20:47 UTC (permalink / raw)
To: qemu-devel
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, Blue Swirl, khoa,
Stefan Hajnoczi, Paolo Bonzini, asias
The virtio-blk-data-plane feature is easy to integrate into
hw/virtio-blk.c. The data plane can be started and stopped similar to
vhost-net.
Users can take advantage of the virtio-blk-data-plane feature using the
new -device virtio-blk-pci,x-data-plane=on property.
The x-data-plane name was chosen because at this stage the feature is
experimental and likely to see changes in the future.
If the VM configuration does not support virtio-blk-data-plane an error
message is printed. Although we could fall back to regular virtio-blk,
I prefer the explicit approach since it prompts the user to fix their
configuration if they want the performance benefit of
virtio-blk-data-plane.
Limitations:
* Only format=raw is supported
* Live migration is not supported
* Block jobs, hot unplug, and other operations fail with -EBUSY
* I/O throttling limits are ignored
* Only Linux hosts are supported due to Linux AIO usage
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/virtio-blk.c | 28 +++++++++++++++++++++++++++-
hw/virtio-blk.h | 1 +
hw/virtio-pci.c | 3 +++
3 files changed, 31 insertions(+), 1 deletion(-)
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index e25cc96..678e812 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -17,6 +17,7 @@
#include "hw/block-common.h"
#include "blockdev.h"
#include "virtio-blk.h"
+#include "hw/dataplane/virtio-blk.h"
#include "scsi-defs.h"
#ifdef __linux__
# include <scsi/sg.h>
@@ -33,6 +34,7 @@ typedef struct VirtIOBlock
VirtIOBlkConf *blk;
unsigned short sector_mask;
DeviceState *qdev;
+ VirtIOBlockDataPlane *dataplane;
} VirtIOBlock;
static VirtIOBlock *to_virtio_blk(VirtIODevice *vdev)
@@ -407,6 +409,14 @@ static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
.num_writes = 0,
};
+ /* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
+ * dataplane here instead of waiting for .set_status().
+ */
+ if (s->dataplane) {
+ virtio_blk_data_plane_start(s->dataplane);
+ return;
+ }
+
while ((req = virtio_blk_get_request(s))) {
virtio_blk_handle_request(req, &mrb);
}
@@ -446,8 +456,13 @@ static void virtio_blk_dma_restart_cb(void *opaque, int running,
{
VirtIOBlock *s = opaque;
- if (!running)
+ if (!running) {
+ /* qemu_drain_all() doesn't know about data plane, quiesce here */
+ if (s->dataplane) {
+ virtio_blk_data_plane_drain(s->dataplane);
+ }
return;
+ }
if (!s->bh) {
s->bh = qemu_bh_new(virtio_blk_dma_restart_bh, s);
@@ -538,6 +553,10 @@ static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status)
VirtIOBlock *s = to_virtio_blk(vdev);
uint32_t features;
+ if (s->dataplane && !(status & VIRTIO_CONFIG_S_DRIVER)) {
+ virtio_blk_data_plane_stop(s->dataplane);
+ }
+
if (!(status & VIRTIO_CONFIG_S_DRIVER_OK)) {
return;
}
@@ -635,6 +654,10 @@ VirtIODevice *virtio_blk_init(DeviceState *dev, VirtIOBlkConf *blk)
s->sector_mask = (s->conf->logical_block_size / BDRV_SECTOR_SIZE) - 1;
s->vq = virtio_add_queue(&s->vdev, 128, virtio_blk_handle_output);
+ if (!virtio_blk_data_plane_create(&s->vdev, blk, &s->dataplane)) {
+ virtio_cleanup(&s->vdev);
+ return NULL;
+ }
qemu_add_vm_change_state_handler(virtio_blk_dma_restart_cb, s);
s->qdev = dev;
@@ -652,6 +675,9 @@ VirtIODevice *virtio_blk_init(DeviceState *dev, VirtIOBlkConf *blk)
void virtio_blk_exit(VirtIODevice *vdev)
{
VirtIOBlock *s = to_virtio_blk(vdev);
+
+ virtio_blk_data_plane_destroy(s->dataplane);
+ s->dataplane = NULL;
unregister_savevm(s->qdev, "virtio-blk", s);
blockdev_mark_auto_del(s->bs);
virtio_cleanup(vdev);
diff --git a/hw/virtio-blk.h b/hw/virtio-blk.h
index f0740d0..53d7971 100644
--- a/hw/virtio-blk.h
+++ b/hw/virtio-blk.h
@@ -105,6 +105,7 @@ struct VirtIOBlkConf
char *serial;
uint32_t scsi;
uint32_t config_wce;
+ uint32_t data_plane;
};
#define DEFINE_VIRTIO_BLK_FEATURES(_state, _field) \
diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 71f4fb5..32cc910 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -897,6 +897,9 @@ static Property virtio_blk_properties[] = {
#endif
DEFINE_PROP_BIT("config-wce", VirtIOPCIProxy, blk.config_wce, 0, true),
DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags, VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true),
+#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE
+ DEFINE_PROP_BIT("x-data-plane", VirtIOPCIProxy, blk.data_plane, 0, false),
+#endif
DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, 2),
DEFINE_VIRTIO_BLK_FEATURES(VirtIOPCIProxy, host_features),
DEFINE_PROP_END_OF_LIST(),
--
1.8.0.1
^ permalink raw reply related [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
` (10 preceding siblings ...)
2012-12-05 20:47 ` [Qemu-devel] [PATCH v5 11/11] virtio-blk: add x-data-plane=on|off performance feature Stefan Hajnoczi
@ 2012-12-06 11:38 ` Michael S. Tsirkin
2012-12-07 6:12 ` Stefan Hajnoczi
2012-12-07 2:43 ` Liu Yuan
12 siblings, 1 reply; 34+ messages in thread
From: Michael S. Tsirkin @ 2012-12-06 11:38 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Kevin Wolf, Anthony Liguori, qemu-devel, Blue Swirl, khoa,
Paolo Bonzini, asias
On Wed, Dec 05, 2012 at 09:46:59PM +0100, Stefan Hajnoczi wrote:
> This series adds the -device virtio-blk-pci,x-data-plane=on property that
> enables a high performance I/O codepath. A dedicated thread is used to process
> virtio-blk requests outside the global mutex and without going through the QEMU
> block layer.
>
> Khoa Huynh <khoa@us.ibm.com> reported an increase from 140,000 IOPS to 600,000
> IOPS for a single VM using virtio-blk-data-plane in July:
>
> http://comments.gmane.org/gmane.comp.emulators.kvm.devel/94580
>
> The virtio-blk-data-plane approach was originally presented at Linux Plumbers
> Conference 2010. The following slides contain a brief overview:
>
> http://linuxplumbersconf.org/2010/ocw/system/presentations/651/original/Optimizing_the_QEMU_Storage_Stack.pdf
>
> The basic approach is:
> 1. Each virtio-blk device has a thread dedicated to handling ioeventfd
> signalling when the guest kicks the virtqueue.
> 2. Requests are processed without going through the QEMU block layer using
> Linux AIO directly.
> 3. Completion interrupts are injected via irqfd from the dedicated thread.
>
> To try it out:
>
> qemu -drive if=none,id=drive0,cache=none,aio=native,format=raw,file=...
> -device virtio-blk-pci,drive=drive0,scsi=off,x-data-plane=on
>
> Limitations:
> * Only format=raw is supported
> * Live migration is not supported
> * Block jobs, hot unplug, and other operations fail with -EBUSY
> * I/O throttling limits are ignored
> * Only Linux hosts are supported due to Linux AIO usage
>
> The code has reached a stage where I feel it is ready to merge. Users have
> been playing with it for some time and want the significant performance boost.
>
> We are refactoring QEMU to get rid of the global mutex. I believe that
> virtio-blk-data-plane can eventually become the default mode of operation.
>
> Instead of waiting for global mutex removal efforts to finish, I want to use
> virtio-blk-data-plane as an example device for AioContext and threaded hw
> dispatch refactoring. This means:
>
> 1. When the block layer can bind to an AioContext and execute I/O outside the
> global mutex, virtio-blk-data-plane can use this (and gain image format
> support).
>
> 2. When hw dispatch no longer needs the global mutex we can use hw/virtio.c
> again and perhaps run a pool of iothreads instead of dedicated data plane
> threads.
>
> But in the meantime, I have cleaned up the virtio-blk-data-plane code so that
> it can be merged as an experimental feature.
I mostly looked at the virtio side of the patchset.
I don't see any bugs here. I sent some improvement suggestions but
we can do them in tree as well.
> v5:
> * Omit memory regions with dirty logging enabled from hostmem [Michael]
> * Add doc comment about quiescing requests across memory hot unplug [Michael]
> * Clarify which Linux vhost version the vring code originates from [Michael]
> * Break up indirect vring buffer into 1 hostmem_lookup() per descriptor [Michael]
> * Barriers in hw/dataplane/vring.c to force fields to be loaded [Michael]
> * split vring_set_notification() into enable/disable [Paolo]
> * barriers in vring.c instead of virtio-blk.c [Michael]
> * move setup code from hw/virtio-blk.c into hw/dataplane/virtio-blk.c [Michael]
>
> * Note I did not get rid of the mutex+condvar approach to draining requests.
> I've had good feedback on the performance of the patch series so I'm not
> worried about eliminating the lock (it's very rarely contended). Hope
> Michael and Paolo are okay with this approach.
>
> v4:
> * Add qemu_iovec_concat_iov() [Paolo]
> * Use QEMUIOVector to copy out virtio_blk_inhdr [Michael, Paolo]
>
> v3:
> * Don't assume iovec layout [Michael]
> * Better naming for hostmem.c MemoryListener callbacks [Don]
> * More vring quarantining if commands are bogus instead of exiting [Blue]
>
> v2:
> * Use MemoryListener for thread-safe memory mapping [Paolo, Anthony, and everyone else pointed this out ;-)]
> * Quarantine invalid vring instead of exiting [Blue]
> * Replace __u16 kernel types with uint16_t [Blue]
>
> Changes from the RFC v9:
> * Add x-data-plane=on|off option and coexist with regular virtio-blk code
> * Create thread from BH so it inherits iothread cpusets
> * Drain requests on vm_stop() so stopped guest does not access image file
> * Add migration blocker
> * Add bdrv_in_use() to prevent block jobs and other operations that can interfere
> * Drop IOQueue request merging for simplicity
> * Drop ioctl interrupt injection and always use irqfd for simplicity
> * Major cleanup to split up source files
> * Rebase from qemu-kvm.git onto qemu.git
> * Address Michael Tsirkin's review comments
>
> Stefan Hajnoczi (11):
> raw-posix: add raw_get_aio_fd() for virtio-blk-data-plane
> configure: add CONFIG_VIRTIO_BLK_DATA_PLANE
> dataplane: add host memory mapping code
> dataplane: add virtqueue vring code
> dataplane: add event loop
> dataplane: add Linux AIO request queue
> iov: add iov_discard() to remove data
> test-iov: add iov_discard() testcase
> iov: add qemu_iovec_concat_iov()
> dataplane: add virtio-blk data plane code
> virtio-blk: add x-data-plane=on|off performance feature
>
> block.h | 9 +
> block/raw-posix.c | 34 ++++
> configure | 21 ++
> hw/Makefile.objs | 2 +-
> hw/dataplane/Makefile.objs | 3 +
> hw/dataplane/event-poll.c | 109 +++++++++++
> hw/dataplane/event-poll.h | 40 ++++
> hw/dataplane/hostmem.c | 173 +++++++++++++++++
> hw/dataplane/hostmem.h | 57 ++++++
> hw/dataplane/ioq.c | 118 ++++++++++++
> hw/dataplane/ioq.h | 57 ++++++
> hw/dataplane/virtio-blk.c | 463 +++++++++++++++++++++++++++++++++++++++++++++
> hw/dataplane/virtio-blk.h | 43 +++++
> hw/dataplane/vring.c | 361 +++++++++++++++++++++++++++++++++++
> hw/dataplane/vring.h | 63 ++++++
> hw/virtio-blk.c | 28 ++-
> hw/virtio-blk.h | 1 +
> hw/virtio-pci.c | 3 +
> iov.c | 80 ++++++--
> iov.h | 13 ++
> qemu-common.h | 3 +
> tests/test-iov.c | 129 +++++++++++++
> trace-events | 9 +
> 23 files changed, 1805 insertions(+), 14 deletions(-)
> create mode 100644 hw/dataplane/Makefile.objs
> create mode 100644 hw/dataplane/event-poll.c
> create mode 100644 hw/dataplane/event-poll.h
> create mode 100644 hw/dataplane/hostmem.c
> create mode 100644 hw/dataplane/hostmem.h
> create mode 100644 hw/dataplane/ioq.c
> create mode 100644 hw/dataplane/ioq.h
> create mode 100644 hw/dataplane/virtio-blk.c
> create mode 100644 hw/dataplane/virtio-blk.h
> create mode 100644 hw/dataplane/vring.c
> create mode 100644 hw/dataplane/vring.h
>
> --
> 1.8.0.1
^ permalink raw reply [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane
2012-12-06 11:38 ` [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Michael S. Tsirkin
@ 2012-12-07 6:12 ` Stefan Hajnoczi
0 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-07 6:12 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Kevin Wolf, Anthony Liguori, qemu-devel, Blue Swirl, khoa,
Paolo Bonzini, asias
On Thu, Dec 06, 2012 at 01:38:28PM +0200, Michael S. Tsirkin wrote:
> On Wed, Dec 05, 2012 at 09:46:59PM +0100, Stefan Hajnoczi wrote:
> > This series adds the -device virtio-blk-pci,x-data-plane=on property that
> > enables a high performance I/O codepath. A dedicated thread is used to process
> > virtio-blk requests outside the global mutex and without going through the QEMU
> > block layer.
> >
> > Khoa Huynh <khoa@us.ibm.com> reported an increase from 140,000 IOPS to 600,000
> > IOPS for a single VM using virtio-blk-data-plane in July:
> >
> > http://comments.gmane.org/gmane.comp.emulators.kvm.devel/94580
> >
> > The virtio-blk-data-plane approach was originally presented at Linux Plumbers
> > Conference 2010. The following slides contain a brief overview:
> >
> > http://linuxplumbersconf.org/2010/ocw/system/presentations/651/original/Optimizing_the_QEMU_Storage_Stack.pdf
> >
> > The basic approach is:
> > 1. Each virtio-blk device has a thread dedicated to handling ioeventfd
> > signalling when the guest kicks the virtqueue.
> > 2. Requests are processed without going through the QEMU block layer using
> > Linux AIO directly.
> > 3. Completion interrupts are injected via irqfd from the dedicated thread.
> >
> > To try it out:
> >
> > qemu -drive if=none,id=drive0,cache=none,aio=native,format=raw,file=...
> > -device virtio-blk-pci,drive=drive0,scsi=off,x-data-plane=on
> >
> > Limitations:
> > * Only format=raw is supported
> > * Live migration is not supported
> > * Block jobs, hot unplug, and other operations fail with -EBUSY
> > * I/O throttling limits are ignored
> > * Only Linux hosts are supported due to Linux AIO usage
> >
> > The code has reached a stage where I feel it is ready to merge. Users have
> > been playing with it for some time and want the significant performance boost.
> >
> > We are refactoring QEMU to get rid of the global mutex. I believe that
> > virtio-blk-data-plane can eventually become the default mode of operation.
> >
> > Instead of waiting for global mutex removal efforts to finish, I want to use
> > virtio-blk-data-plane as an example device for AioContext and threaded hw
> > dispatch refactoring. This means:
> >
> > 1. When the block layer can bind to an AioContext and execute I/O outside the
> > global mutex, virtio-blk-data-plane can use this (and gain image format
> > support).
> >
> > 2. When hw dispatch no longer needs the global mutex we can use hw/virtio.c
> > again and perhaps run a pool of iothreads instead of dedicated data plane
> > threads.
> >
> > But in the meantime, I have cleaned up the virtio-blk-data-plane code so that
> > it can be merged as an experimental feature.
>
> I mostly looked at the virtio side of the patchset.
> I don't see any bugs here. I sent some improvement suggestions but
> we can do them in tree as well.
Thanks Michael. I'll send follow-up patches to split the iov_discard()
function and to address config-wce.
Stefan
^ permalink raw reply [flat|nested] 34+ messages in thread
* Re: [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane
2012-12-05 20:46 [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Stefan Hajnoczi
` (11 preceding siblings ...)
2012-12-06 11:38 ` [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane Michael S. Tsirkin
@ 2012-12-07 2:43 ` Liu Yuan
2012-12-07 5:46 ` Stefan Hajnoczi
12 siblings, 1 reply; 34+ messages in thread
From: Liu Yuan @ 2012-12-07 2:43 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, qemu-devel,
Blue Swirl, khoa, Paolo Bonzini, asias
Hi Stefan,
On 12/06/2012 04:46 AM, Stefan Hajnoczi wrote:
> Limitations:
> * Only format=raw is supported
The boost number looks promising, but support of other format(which
might as well fit into this new IO path design) is in the plan? It seems
that bypassing block layer would end up adding yet another 'block layer'
as we add more format support.
Thanks,
Yuan
^ permalink raw reply [flat|nested] 34+ messages in thread* Re: [Qemu-devel] [PATCH v5 00/11] virtio: virtio-blk data plane
2012-12-07 2:43 ` Liu Yuan
@ 2012-12-07 5:46 ` Stefan Hajnoczi
0 siblings, 0 replies; 34+ messages in thread
From: Stefan Hajnoczi @ 2012-12-07 5:46 UTC (permalink / raw)
To: Liu Yuan
Cc: Kevin Wolf, Anthony Liguori, Michael S. Tsirkin, qemu-devel,
Blue Swirl, khoa, Paolo Bonzini, asias
On Fri, Dec 07, 2012 at 10:43:24AM +0800, Liu Yuan wrote:
> On 12/06/2012 04:46 AM, Stefan Hajnoczi wrote:
> > Limitations:
> > * Only format=raw is supported
>
> The boost number looks promising, but support of other format(which
> might as well fit into this new IO path design) is in the plan? It seems
> that bypassing block layer would end up adding yet another 'block layer'
> as we add more format support.
Right, that's why the next step is to complete the AioContext work that
Paolo recently contributed. It will allow us to run the QEMU block
layer outside the global mutex.
Once that refactoring is complete the data plane thread will be able to
run image format code.
We'll need to be careful so as not to lose the level of performance that
it achieves right now, but there is no fundamental reason why we cannot
continue to keep this level of performance while still supporting image
formats.
Stefan
^ permalink raw reply [flat|nested] 34+ messages in thread