On Thu, 29 Dec 2022 13:03:36 +0200 Avihai Horon <avih...@nvidia.com> wrote:
> Currently, if IOMMU of a VFIO container doesn't support dirty page > tracking, migration is blocked. This is because a DMA-able VFIO device > can dirty RAM pages without updating QEMU about it, thus breaking the > migration. > > However, this doesn't mean that migration can't be done at all. > In such case, allow migration and let QEMU VFIO code mark the entire > bitmap dirty. > > This guarantees that all pages that might have gotten dirty are reported > back, and thus guarantees a valid migration even without VFIO IOMMU > dirty tracking support. > > The motivation for this patch is the introduction of iommufd [1]. > iommufd can directly implement the /dev/vfio/vfio container IOCTLs by > mapping them into its internal ops, allowing the usage of these IOCTLs > over iommufd. However, VFIO IOMMU dirty tracking is not supported by > this VFIO compatibility API. > > This patch will allow migration by hosts that use the VFIO compatibility > API and prevent migration regressions caused by the lack of VFIO IOMMU > dirty tracking support. > > [1] > https://lore.kernel.org/kvm/0-v6-a196d26f289e+11787-iommufd_...@nvidia.com/ > > Signed-off-by: Avihai Horon <avih...@nvidia.com> > --- > hw/vfio/common.c | 100 ++++++++++++++++++++++++++------------------ > hw/vfio/migration.c | 3 +- > 2 files changed, 61 insertions(+), 42 deletions(-) > > diff --git a/hw/vfio/common.c b/hw/vfio/common.c > index 130e5d1dc7..67104e2fc2 100644 > --- a/hw/vfio/common.c > +++ b/hw/vfio/common.c > @@ -397,51 +397,61 @@ static int vfio_dma_unmap_bitmap(VFIOContainer > *container, > IOMMUTLBEntry *iotlb) > { > struct vfio_iommu_type1_dma_unmap *unmap; > - struct vfio_bitmap *bitmap; > + struct vfio_bitmap *vbitmap; > + unsigned long *bitmap; > + uint64_t bitmap_size; > uint64_t pages = REAL_HOST_PAGE_ALIGN(size) / qemu_real_host_page_size(); > int ret; > > - unmap = g_malloc0(sizeof(*unmap) + sizeof(*bitmap)); > + unmap = g_malloc0(sizeof(*unmap) + sizeof(*vbitmap)); > > - unmap->argsz = sizeof(*unmap) + sizeof(*bitmap); > + unmap->argsz = sizeof(*unmap); > unmap->iova = iova; > unmap->size = size; > - unmap->flags |= VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP; > - bitmap = (struct vfio_bitmap *)&unmap->data; > > + bitmap_size = ROUND_UP(pages, sizeof(__u64) * BITS_PER_BYTE) / > + BITS_PER_BYTE; > + bitmap = g_try_malloc0(bitmap_size); > + if (!bitmap) { > + ret = -ENOMEM; > + goto unmap_exit; > + } > + > + if (!container->dirty_pages_supported) { > + bitmap_set(bitmap, 0, pages); > + goto do_unmap; > + } > + > + unmap->argsz += sizeof(*vbitmap); > + unmap->flags = VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP; > + > + vbitmap = (struct vfio_bitmap *)&unmap->data; > + vbitmap->data = (__u64 *)bitmap; > /* > * cpu_physical_memory_set_dirty_lebitmap() supports pages in bitmap of > * qemu_real_host_page_size to mark those dirty. Hence set bitmap_pgsize > * to qemu_real_host_page_size. > */ > + vbitmap->pgsize = qemu_real_host_page_size(); > + vbitmap->size = bitmap_size; > > - bitmap->pgsize = qemu_real_host_page_size(); > - bitmap->size = ROUND_UP(pages, sizeof(__u64) * BITS_PER_BYTE) / > - BITS_PER_BYTE; > - > - if (bitmap->size > container->max_dirty_bitmap_size) { > - error_report("UNMAP: Size of bitmap too big 0x%"PRIx64, > - (uint64_t)bitmap->size); > + if (bitmap_size > container->max_dirty_bitmap_size) { > + error_report("UNMAP: Size of bitmap too big 0x%"PRIx64, bitmap_size); > ret = -E2BIG; > goto unmap_exit; > } > > - bitmap->data = g_try_malloc0(bitmap->size); > - if (!bitmap->data) { > - ret = -ENOMEM; > - goto unmap_exit; > - } > - > +do_unmap: > ret = ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, unmap); > if (!ret) { > - cpu_physical_memory_set_dirty_lebitmap((unsigned long *)bitmap->data, > - iotlb->translated_addr, pages); > + cpu_physical_memory_set_dirty_lebitmap(bitmap, > iotlb->translated_addr, > + pages); > } else { > error_report("VFIO_UNMAP_DMA with DIRTY_BITMAP : %m"); > } > > - g_free(bitmap->data); > unmap_exit: > + g_free(bitmap); > g_free(unmap); > return ret; > } > @@ -460,8 +470,7 @@ static int vfio_dma_unmap(VFIOContainer *container, > .size = size, > }; > > - if (iotlb && container->dirty_pages_supported && > - vfio_devices_all_running_and_saving(container)) { > + if (iotlb && vfio_devices_all_running_and_saving(container)) { > return vfio_dma_unmap_bitmap(container, iova, size, iotlb); > } Seems like it would be simpler to follow the non-dirty_pages_supported path here and follow-up with a condition to call cpu_physical_memory_set_dirty_range() rather than try to make the bitmap path serve double-duty. > > @@ -1201,6 +1210,10 @@ static void vfio_set_dirty_page_tracking(VFIOContainer > *container, bool start) > .argsz = sizeof(dirty), > }; > > + if (!container->dirty_pages_supported) { > + return; > + } > + > if (start) { > dirty.flags = VFIO_IOMMU_DIRTY_PAGES_FLAG_START; > } else { > @@ -1231,11 +1244,26 @@ static void > vfio_listener_log_global_stop(MemoryListener *listener) > static int vfio_get_dirty_bitmap(VFIOContainer *container, uint64_t iova, > uint64_t size, ram_addr_t ram_addr) > { > - struct vfio_iommu_type1_dirty_bitmap *dbitmap; > + struct vfio_iommu_type1_dirty_bitmap *dbitmap = NULL; > struct vfio_iommu_type1_dirty_bitmap_get *range; > + unsigned long *bitmap; > + uint64_t bitmap_size; > uint64_t pages; > int ret; > > + pages = REAL_HOST_PAGE_ALIGN(size) / qemu_real_host_page_size(); > + bitmap_size = ROUND_UP(pages, sizeof(__u64) * BITS_PER_BYTE) / > + BITS_PER_BYTE; > + bitmap = g_try_malloc0(bitmap_size); > + if (!bitmap) { > + return -ENOMEM; > + } > + > + if (!container->dirty_pages_supported) { > + bitmap_set(bitmap, 0, pages); > + goto set_dirty; > + } Same here, why are we bothering to allocate and mark a bitmap dirty just to appease code we don't need instead of: if (!container->dirty_pages_supported) { cpu_physical_memory_set_dirty_range(...) return 0; } Thanks, Alex > + > dbitmap = g_malloc0(sizeof(*dbitmap) + sizeof(*range)); > > dbitmap->argsz = sizeof(*dbitmap) + sizeof(*range); > @@ -1250,15 +1278,8 @@ static int vfio_get_dirty_bitmap(VFIOContainer > *container, uint64_t iova, > * to qemu_real_host_page_size. > */ > range->bitmap.pgsize = qemu_real_host_page_size(); > - > - pages = REAL_HOST_PAGE_ALIGN(range->size) / qemu_real_host_page_size(); > - range->bitmap.size = ROUND_UP(pages, sizeof(__u64) * BITS_PER_BYTE) / > - BITS_PER_BYTE; > - range->bitmap.data = g_try_malloc0(range->bitmap.size); > - if (!range->bitmap.data) { > - ret = -ENOMEM; > - goto err_out; > - } > + range->bitmap.size = bitmap_size; > + range->bitmap.data = (__u64 *)bitmap; > > ret = ioctl(container->fd, VFIO_IOMMU_DIRTY_PAGES, dbitmap); > if (ret) { > @@ -1268,13 +1289,13 @@ static int vfio_get_dirty_bitmap(VFIOContainer > *container, uint64_t iova, > goto err_out; > } > > - cpu_physical_memory_set_dirty_lebitmap((unsigned long > *)range->bitmap.data, > - ram_addr, pages); > +set_dirty: > + cpu_physical_memory_set_dirty_lebitmap(bitmap, ram_addr, pages); > > - trace_vfio_get_dirty_bitmap(container->fd, range->iova, range->size, > - range->bitmap.size, ram_addr); > + trace_vfio_get_dirty_bitmap(container->fd, iova, size, bitmap_size, > + ram_addr); > err_out: > - g_free(range->bitmap.data); > + g_free(bitmap); > g_free(dbitmap); > > return ret; > @@ -1409,8 +1430,7 @@ static void vfio_listener_log_sync(MemoryListener > *listener, > { > VFIOContainer *container = container_of(listener, VFIOContainer, > listener); > > - if (vfio_listener_skipped_section(section) || > - !container->dirty_pages_supported) { > + if (vfio_listener_skipped_section(section)) { > return; > } > > diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c > index 09fe7c1de2..552c2313b2 100644 > --- a/hw/vfio/migration.c > +++ b/hw/vfio/migration.c > @@ -860,11 +860,10 @@ int64_t vfio_mig_bytes_transferred(void) > > int vfio_migration_probe(VFIODevice *vbasedev, Error **errp) > { > - VFIOContainer *container = vbasedev->group->container; > struct vfio_region_info *info = NULL; > int ret = -ENOTSUP; > > - if (!vbasedev->enable_migration || !container->dirty_pages_supported) { > + if (!vbasedev->enable_migration) { > goto add_blocker; > } >
