Re: [Qemu-devel] [Qemu-ppc] [PATCH qemu v13 11/16] vfio: spapr: Add SPAPR IOMMU v2 support (DMA memory preregistering)

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 03/03/2016 05:30 PM, David Gibson wrote:
> On Tue, Mar 01, 2016 at 08:10:36PM +1100, 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 device
>> 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 does not change the guest visible interface.
>>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>> ---
>>   hw/vfio/Makefile.objs         |   1 +
>>   hw/vfio/common.c              |  39 +++++++++---
>>   hw/vfio/prereg.c              | 138 ++++++++++++++++++++++++++++++++++++++++++
>>   include/hw/vfio/vfio-common.h |   4 ++
>>   trace-events                  |   2 +
>>   5 files changed, 175 insertions(+), 9 deletions(-)
>>   create mode 100644 hw/vfio/prereg.c
>>
>> diff --git a/hw/vfio/Makefile.objs b/hw/vfio/Makefile.objs
>> index ceddbb8..5800e0e 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) += prereg.o
>>   endif
>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
>> index 3aaa6b5..f2a03e0 100644
>> --- a/hw/vfio/common.c
>> +++ b/hw/vfio/common.c
>> @@ -531,6 +531,9 @@ static const MemoryListener vfio_iommu_listener = {
>>   static void vfio_listener_release(VFIOContainer *container)
>>   {
>>       memory_listener_unregister(&container->iommu_listener.listener);
>> +    if (container->iommu_type == VFIO_SPAPR_TCE_v2_IOMMU) {
>> +        memory_listener_unregister(&container->prereg_listener.listener);
>> +    }
>>   }
>>
>>   int vfio_mmap_region(Object *obj, VFIORegion *region,
>> @@ -722,8 +725,8 @@ 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;
>> @@ -748,8 +751,10 @@ 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) {
>> @@ -757,7 +762,9 @@ 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);
>
> It'd be nice to consolidate the setting of container->iommu_type and
> then the SET_IOMMU ioctl() rather than having more or less duplicated
> logic for Type1 and SPAPR, but it's not a big deal.


May be but I cannot think of any nice way of doing this though.


>
>>           if (ret) {
>>               error_report("vfio: failed to set iommu for container: %m");
>>               ret = -errno;
>> @@ -769,11 +776,25 @@ 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.container = container;
>> +            container->prereg_listener.listener = vfio_prereg_listener;
>> +
>> +            memory_listener_register(&container->prereg_listener.listener,
>> +                                     &address_space_memory);
>
> This assumes that the target address space of the (guest) IOMMU is
> address_space_memory.  Which is fine - vfio already assumes that - but
> it reminds me that it'd be nice to have an explicit check for that (I
> guess it would have to go in vfio_iommu_map_notify()).  So that if
> someone constructs a machine where that's not the case, it'll at least
> be obvious why VFIO isn't working.

Ok, I'll add a small patch for this in the next respin.


>
>> +            if (container->error) {
>> +                error_report("vfio: RAM memory listener initialization failed for container");
>> +                memory_listener_unregister(
>> +                    &container->prereg_listener.listener);
>> +                goto free_container_exit;
>> +            }
>>           }
>
> Looks like you don't have an error path which will handle the case
> where the prereg listener is registered, but registering the normal
> PCI AS listener fails - I believe you will fail to unregister the
> prereg listener in that case.


In this case, the control goes to listener_release_exit: which calls 
vfio_listener_release() which unregisters both listeners (it is a few 
chunks above).



>>           /*
>> diff --git a/hw/vfio/prereg.c b/hw/vfio/prereg.c
>> new file mode 100644
>> index 0000000..66cd696
>> --- /dev/null
>> +++ b/hw/vfio/prereg.c
>> @@ -0,0 +1,138 @@
>> +/*
>> + * 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 <sys/ioctl.h>
>> +#include <linux/vfio.h>
>> +
>> +#include "hw/vfio/vfio-common.h"
>> +#include "hw/vfio/vfio.h"
>> +#include "qemu/error-report.h"
>> +#include "trace.h"
>> +
>> +static bool vfio_prereg_listener_skipped_section(MemoryRegionSection *section)
>> +{
>> +    return (!memory_region_is_ram(section->mr) &&
>> +            !memory_region_is_iommu(section->mr)) ||
>> +            memory_region_is_skip_dump(section->mr);
>> +}
>> +
>> +static void vfio_prereg_listener_region_add(MemoryListener *listener,
>> +                                            MemoryRegionSection *section)
>> +{
>> +    VFIOMemoryListener *vlistener = container_of(listener, VFIOMemoryListener,
>> +                                                 listener);
>> +    VFIOContainer *container = vlistener->container;
>> +    hwaddr iova;
>> +    Int128 llend;
>> +    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;
>> +    }
>
> You should probably explicitly check for IOMMU regions and abort if
> you find one.  An IOMMU AS appearing within address_space_memory would
> be bad news.


Oh, vfio_prereg_listener_skipped_section() allows memory_region_is_iommu(), 
I'll remove it.



>
>> +    if (unlikely((section->offset_within_address_space & ~page_mask) !=
>> +                 (section->offset_within_region & ~page_mask))) {
>> +        error_report("%s received unaligned region", __func__);
>> +        return;
>> +    }
>> +
>> +    iova = ROUND_UP(section->offset_within_address_space, ~page_mask + 1);
>
> iova is a terrible name here.  This is *not* an IOVA, but a real
> memory address.


I'll do s/iova/gpa/


>
>> +    llend = int128_make64(section->offset_within_address_space);
>> +    llend = int128_add(llend, section->size);
>> +    llend = int128_and(llend, int128_exts64(page_mask));
>> +
>> +    if (int128_ge(int128_make64(iova), llend)) {
>> +        return;
>
> IIUC, if we get here something has gone horribly wrong in our machine
> setup, and we shold probably just abort.  Same goes for the similar
> test in the IOVA listener, of course.


I do not have a good message candidate though. May be
hw_error("vfio: Broken section alignment");
?


>
>> +    }
>> +
>> +    memory_region_ref(section->mr);
>> +
>> +    reg.vaddr = (__u64) memory_region_get_ram_ptr(section->mr) +
>> +        section->offset_within_region +
>> +        (iova - section->offset_within_address_space);
>> +    reg.size = int128_get64(llend) - iova;
>> +
>> +    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: DMA mapping failed, unable to continue");
>
> Wrong error message.
>
>> +        }
>> +    }
>> +}
>> +
>> +static void vfio_prereg_listener_region_del(MemoryListener *listener,
>> +                                            MemoryRegionSection *section)
>> +{
>> +    VFIOMemoryListener *vlistener = container_of(listener, VFIOMemoryListener,
>> +                                                 listener);
>> +    VFIOContainer *container = vlistener->container;
>> +    hwaddr iova, 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))) {
>> +        error_report("%s received unaligned region", __func__);
>> +        return;
>> +    }
>> +
>> +    iova = ROUND_UP(section->offset_within_address_space, ~page_mask + 1);
>> +    end = (section->offset_within_address_space + int128_get64(section->size)) &
>> +        page_mask;
>> +
>> +    if (iova >= end) {
>> +        return;
>> +    }
>> +
>> +    reg.vaddr = (__u64) memory_region_get_ram_ptr(section->mr) +
>> +        section->offset_within_region +
>> +        (iova - section->offset_within_address_space);
>> +    reg.size = end - iova;
>> +
>> +    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 b6b736c..bcbc5cb 100644
>> --- a/include/hw/vfio/vfio-common.h
>> +++ b/include/hw/vfio/vfio-common.h
>> @@ -70,6 +70,8 @@ typedef struct VFIOContainer {
>>       VFIOAddressSpace *space;
>>       int fd; /* /dev/vfio/vfio, empowered by the attached groups */
>>       VFIOMemoryListener iommu_listener;
>> +    VFIOMemoryListener prereg_listener;
>> +    unsigned iommu_type;
>>       int error;
>>       bool initialized;
>>       /*
>> @@ -146,4 +148,6 @@ extern const MemoryRegionOps vfio_region_ops;
>>   extern QLIST_HEAD(vfio_group_head, VFIOGroup) vfio_group_list;
>>   extern QLIST_HEAD(vfio_as_head, VFIOAddressSpace) vfio_address_spaces;
>>
>> +extern const MemoryListener vfio_prereg_listener;
>> +
>>   #endif /* !HW_VFIO_VFIO_COMMON_H */
>> diff --git a/trace-events b/trace-events
>> index 4b6ea70..f5335ec 100644
>> --- a/trace-events
>> +++ b/trace-events
>> @@ -1725,6 +1725,8 @@ vfio_disconnect_container(int fd) "close container->fd=%d"
>>   vfio_put_group(int fd) "close group->fd=%d"
>>   vfio_get_device(const char * name, unsigned int flags, unsigned int num_regions, unsigned int num_irqs) "Device %s flags: %u, regions: %u, irqs: %u"
>>   vfio_put_base_device(int fd) "close vdev->fd=%d"
>> +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_populate_regions(int region_index, unsigned long flag, unsigned long size, int fd, unsigned long offset) "- region %d flags = 0x%lx, size = 0x%lx, fd= %d, offset = 0x%lx"
>


-- 
Alexey