Re: [Qemu-devel] [PATCH qemu v17 07/12] vfio: spapr: Add DMA memory preregistering (SPAPR IOMMU v2)

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Jun 01, 2016 at 06:57:38PM +1000, Alexey Kardashevskiy wrote:
> This makes use of the new "memory registering" feature. The idea is
> to provide the userspace ability to notify the host kernel about pages
> which are going to be used for DMA. Having this information, the host
> kernel can pin them all once per user process, do locked pages
> accounting (once) and not spent time on doing that in real time with
> possible failures which cannot be handled nicely in some cases.
> 
> This adds a prereg memory listener which listens on address_space_memory
> and notifies a VFIO container about memory which needs to be
> pinned/unpinned. VFIO MMIO regions (i.e. "skip dump" regions) are skipped.
> 
> As there is no per-IOMMU-type release() callback anymore, this stores
> the IOMMU type in the container so vfio_listener_release() can determine
> if it needs to unregister @prereg_listener.
> 
> The feature is only enabled for SPAPR IOMMU v2. The host kernel changes
> are required. Since v2 does not need/support VFIO_IOMMU_ENABLE, this does
> not call it when v2 is detected and enabled.
> 
> This enforces guest RAM blocks to be host page size aligned; however
> this is not new as KVM already requires memory slots to be host page
> size aligned.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

Alex, do you think this is ready to go now?

> ---
> Changes:
> v17:
> * s/prereg\.c/spapr.c/
> * s/vfio_prereg_gpa_to_ua/vfio_prereg_gpa_to_vaddr/
> * vfio_prereg_listener_skipped_section does hw_error() on IOMMUs
> 
> v16:
> * switched to 64bit math everywhere as there is no chance to see
> region_add on RAM blocks even remotely close to 1<<64bytes.
> 
> v15:
> * banned unaligned sections
> * added an vfio_prereg_gpa_to_ua() helper
> 
> v14:
> * s/free_container_exit/listener_release_exit/g
> * added "if memory_region_is_iommu()" to vfio_prereg_listener_skipped_section
> ---
>  hw/vfio/Makefile.objs         |   1 +
>  hw/vfio/common.c              |  38 +++++++++---
>  hw/vfio/spapr.c               | 137 ++++++++++++++++++++++++++++++++++++++++++
>  include/hw/vfio/vfio-common.h |   4 ++
>  trace-events                  |   2 +
>  5 files changed, 172 insertions(+), 10 deletions(-)
>  create mode 100644 hw/vfio/spapr.c
> 
> diff --git a/hw/vfio/Makefile.objs b/hw/vfio/Makefile.objs
> index ceddbb8..c25e32b 100644
> --- a/hw/vfio/Makefile.objs
> +++ b/hw/vfio/Makefile.objs
> @@ -4,4 +4,5 @@ obj-$(CONFIG_PCI) += pci.o pci-quirks.o
>  obj-$(CONFIG_SOFTMMU) += platform.o
>  obj-$(CONFIG_SOFTMMU) += calxeda-xgmac.o
>  obj-$(CONFIG_SOFTMMU) += amd-xgbe.o
> +obj-$(CONFIG_SOFTMMU) += spapr.o
>  endif
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index f1a12b0..770f630 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -504,6 +504,9 @@ static const MemoryListener vfio_memory_listener = {
>  static void vfio_listener_release(VFIOContainer *container)
>  {
>      memory_listener_unregister(&container->listener);
> +    if (container->iommu_type == VFIO_SPAPR_TCE_v2_IOMMU) {
> +        memory_listener_unregister(&container->prereg_listener);
> +    }
>  }
>  
>  static struct vfio_info_cap_header *
> @@ -862,8 +865,8 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
>              goto free_container_exit;
>          }
>  
> -        ret = ioctl(fd, VFIO_SET_IOMMU,
> -                    v2 ? VFIO_TYPE1v2_IOMMU : VFIO_TYPE1_IOMMU);
> +        container->iommu_type = v2 ? VFIO_TYPE1v2_IOMMU : VFIO_TYPE1_IOMMU;
> +        ret = ioctl(fd, VFIO_SET_IOMMU, container->iommu_type);
>          if (ret) {
>              error_report("vfio: failed to set iommu for container: %m");
>              ret = -errno;
> @@ -888,8 +891,10 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
>          if ((ret == 0) && (info.flags & VFIO_IOMMU_INFO_PGSIZES)) {
>              container->iova_pgsizes = info.iova_pgsizes;
>          }
> -    } else if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_IOMMU)) {
> +    } else if (ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_IOMMU) ||
> +               ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_v2_IOMMU)) {
>          struct vfio_iommu_spapr_tce_info info;
> +        bool v2 = !!ioctl(fd, VFIO_CHECK_EXTENSION, VFIO_SPAPR_TCE_v2_IOMMU);
>  
>          ret = ioctl(group->fd, VFIO_GROUP_SET_CONTAINER, &fd);
>          if (ret) {
> @@ -897,7 +902,9 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
>              ret = -errno;
>              goto free_container_exit;
>          }
> -        ret = ioctl(fd, VFIO_SET_IOMMU, VFIO_SPAPR_TCE_IOMMU);
> +        container->iommu_type =
> +            v2 ? VFIO_SPAPR_TCE_v2_IOMMU : VFIO_SPAPR_TCE_IOMMU;
> +        ret = ioctl(fd, VFIO_SET_IOMMU, container->iommu_type);
>          if (ret) {
>              error_report("vfio: failed to set iommu for container: %m");
>              ret = -errno;
> @@ -909,11 +916,22 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
>           * when container fd is closed so we do not call it explicitly
>           * in this file.
>           */
> -        ret = ioctl(fd, VFIO_IOMMU_ENABLE);
> -        if (ret) {
> -            error_report("vfio: failed to enable container: %m");
> -            ret = -errno;
> -            goto free_container_exit;
> +        if (!v2) {
> +            ret = ioctl(fd, VFIO_IOMMU_ENABLE);
> +            if (ret) {
> +                error_report("vfio: failed to enable container: %m");
> +                ret = -errno;
> +                goto free_container_exit;
> +            }
> +        } else {
> +            container->prereg_listener = vfio_prereg_listener;
> +
> +            memory_listener_register(&container->prereg_listener,
> +                                     &address_space_memory);
> +            if (container->error) {
> +                error_report("vfio: RAM memory listener initialization failed for container");
> +                goto listener_release_exit;
> +            }
>          }
>  
>          /*
> @@ -926,7 +944,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as)
>          if (ret) {
>              error_report("vfio: VFIO_IOMMU_SPAPR_TCE_GET_INFO failed: %m");
>              ret = -errno;
> -            goto free_container_exit;
> +            goto listener_release_exit;
>          }
>          container->min_iova = info.dma32_window_start;
>          container->max_iova = container->min_iova + info.dma32_window_size - 1;
> diff --git a/hw/vfio/spapr.c b/hw/vfio/spapr.c
> new file mode 100644
> index 0000000..f339472
> --- /dev/null
> +++ b/hw/vfio/spapr.c
> @@ -0,0 +1,137 @@
> +/*
> + * DMA memory preregistration
> + *
> + * Authors:
> + *  Alexey Kardashevskiy <aik@ozlabs.ru>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See
> + * the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "cpu.h"
> +#include <sys/ioctl.h>
> +#include <linux/vfio.h>
> +
> +#include "hw/vfio/vfio-common.h"
> +#include "hw/hw.h"
> +#include "qemu/error-report.h"
> +#include "trace.h"
> +
> +static bool vfio_prereg_listener_skipped_section(MemoryRegionSection *section)
> +{
> +    if (memory_region_is_iommu(section->mr)) {
> +        hw_error("Cannot possibly preregister IOMMU memory");
> +    }
> +
> +    return !memory_region_is_ram(section->mr) ||
> +            memory_region_is_skip_dump(section->mr);
> +}
> +
> +static void *vfio_prereg_gpa_to_vaddr(MemoryRegionSection *section, hwaddr gpa)
> +{
> +    return memory_region_get_ram_ptr(section->mr) +
> +        section->offset_within_region +
> +        (gpa - section->offset_within_address_space);
> +}
> +
> +static void vfio_prereg_listener_region_add(MemoryListener *listener,
> +                                            MemoryRegionSection *section)
> +{
> +    VFIOContainer *container = container_of(listener, VFIOContainer,
> +                                            prereg_listener);
> +    const hwaddr gpa = section->offset_within_address_space;
> +    hwaddr end;
> +    int ret;
> +    hwaddr page_mask = qemu_real_host_page_mask;
> +    struct vfio_iommu_spapr_register_memory reg = {
> +        .argsz = sizeof(reg),
> +        .flags = 0,
> +    };
> +
> +    if (vfio_prereg_listener_skipped_section(section)) {
> +        trace_vfio_listener_region_add_skip(
> +                section->offset_within_address_space,
> +                section->offset_within_address_space +
> +                int128_get64(int128_sub(section->size, int128_one())));
> +        return;
> +    }
> +
> +    if (unlikely((section->offset_within_address_space & ~page_mask) ||
> +                 (section->offset_within_region & ~page_mask) ||
> +                 (int128_get64(section->size) & ~page_mask))) {
> +        error_report("%s received unaligned region", __func__);
> +        return;
> +    }
> +
> +    end = section->offset_within_address_space + int128_get64(section->size);
> +    g_assert(gpa < end);
> +
> +    memory_region_ref(section->mr);
> +
> +    reg.vaddr = (__u64) vfio_prereg_gpa_to_vaddr(section, gpa);
> +    reg.size = end - gpa;
> +
> +    ret = ioctl(container->fd, VFIO_IOMMU_SPAPR_REGISTER_MEMORY, &reg);
> +    trace_vfio_ram_register(reg.vaddr, reg.size, ret ? -errno : 0);
> +    if (ret) {
> +        /*
> +         * On the initfn path, store the first error in the container so we
> +         * can gracefully fail.  Runtime, there's not much we can do other
> +         * than throw a hardware error.
> +         */
> +        if (!container->initialized) {
> +            if (!container->error) {
> +                container->error = ret;
> +            }
> +        } else {
> +            hw_error("vfio: Memory registering failed, unable to continue");
> +        }
> +    }
> +}
> +
> +static void vfio_prereg_listener_region_del(MemoryListener *listener,
> +                                            MemoryRegionSection *section)
> +{
> +    VFIOContainer *container = container_of(listener, VFIOContainer,
> +                                            prereg_listener);
> +    const hwaddr gpa = section->offset_within_address_space;
> +    hwaddr end;
> +    int ret;
> +    hwaddr page_mask = qemu_real_host_page_mask;
> +    struct vfio_iommu_spapr_register_memory reg = {
> +        .argsz = sizeof(reg),
> +        .flags = 0,
> +    };
> +
> +    if (vfio_prereg_listener_skipped_section(section)) {
> +        trace_vfio_listener_region_del_skip(
> +                section->offset_within_address_space,
> +                section->offset_within_address_space +
> +                int128_get64(int128_sub(section->size, int128_one())));
> +        return;
> +    }
> +
> +    if (unlikely((section->offset_within_address_space & ~page_mask) ||
> +                 (section->offset_within_region & ~page_mask) ||
> +                 (int128_get64(section->size) & ~page_mask))) {
> +        error_report("%s received unaligned region", __func__);
> +        return;
> +    }
> +
> +    end = section->offset_within_address_space + int128_get64(section->size);
> +    if (gpa >= end) {
> +        return;
> +    }
> +
> +    reg.vaddr = (__u64) vfio_prereg_gpa_to_vaddr(section, gpa);
> +    reg.size = end - gpa;
> +
> +    ret = ioctl(container->fd, VFIO_IOMMU_SPAPR_UNREGISTER_MEMORY, &reg);
> +    trace_vfio_ram_unregister(reg.vaddr, reg.size, ret ? -errno : 0);
> +}
> +
> +const MemoryListener vfio_prereg_listener = {
> +    .region_add = vfio_prereg_listener_region_add,
> +    .region_del = vfio_prereg_listener_region_del,
> +};
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index 0610377..405c3b2 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -73,6 +73,8 @@ typedef struct VFIOContainer {
>      VFIOAddressSpace *space;
>      int fd; /* /dev/vfio/vfio, empowered by the attached groups */
>      MemoryListener listener;
> +    MemoryListener prereg_listener;
> +    unsigned iommu_type;
>      int error;
>      bool initialized;
>      /*
> @@ -158,4 +160,6 @@ int vfio_get_region_info(VFIODevice *vbasedev, int index,
>  int vfio_get_dev_region_info(VFIODevice *vbasedev, uint32_t type,
>                               uint32_t subtype, struct vfio_region_info **info);
>  #endif
> +extern const MemoryListener vfio_prereg_listener;
> +
>  #endif /* !HW_VFIO_VFIO_COMMON_H */
> diff --git a/trace-events b/trace-events
> index de42012..ddb8676 100644
> --- a/trace-events
> +++ b/trace-events
> @@ -1766,6 +1766,8 @@ vfio_region_mmaps_set_enabled(const char *name, bool enabled) "Region %s mmaps e
>  vfio_region_sparse_mmap_header(const char *name, int index, int nr_areas) "Device %s region %d: %d sparse mmap entries"
>  vfio_region_sparse_mmap_entry(int i, unsigned long start, unsigned long end) "sparse entry %d [0x%lx - 0x%lx]"
>  vfio_get_dev_region(const char *name, int index, uint32_t type, uint32_t subtype) "%s index %d, %08x/%0x8"
> +vfio_ram_register(uint64_t va, uint64_t size, int ret) "va=%"PRIx64" size=%"PRIx64" ret=%d"
> +vfio_ram_unregister(uint64_t va, uint64_t size, int ret) "va=%"PRIx64" size=%"PRIx64" ret=%d"
>  
>  # hw/vfio/platform.c
>  vfio_platform_base_device_init(char *name, int groupid) "%s belongs to group #%d"

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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