Re: [PATCH] vfio/migration: fix dirty pages lost bug for ram beyond 3G

[Alex Williamson <alex.williamson@redhat.com>]

On Fri,  6 Mar 2020 17:41:29 +0800
Yan Zhao <yan.y.zhao@intel.com> wrote:

> the start address passing to
> cpu_physical_memory_set_dirty_range() and
> cpu_physical_memory_set_dirty_lebitmap() is the address within the
> ram block plus ram block offset.
> 
> it's safe to set this start address to gpa if total memory is less than
> 3G, as ram block offset for pc.ram is 0. But if memory size is beyond
> 3G, gpa is not equal to the offset in its ram block.
> 
> e.g.
> for gpa 0x100000000, its offset is actually 0xc0000000.
> and for gpa 0x42f500000, its offset should be 0x3EF500000.
> 
> This fix is based on Kirti's VFIO live migration patch set v8.
> https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg05542.html
> (for PATCH v8 11/13
> https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg05553.html
> and PATCH v8 12/13
> https://lists.gnu.org/archive/html/qemu-devel/2019-08/msg05554.html
> }
> 
> The idea behind it should also be applied to other VFIO live migraiton
> patch series below:
> https://lists.gnu.org/archive/html/qemu-devel/2019-11/msg01763.html
> (Kirti v9)
> https://lists.gnu.org/archive/html/qemu-devel/2019-02/msg04912.html
> (Yan)
> https://lists.gnu.org/archive/html/qemu-devel/2018-04/msg01138.html
> (Yulei RFC v4)
> https://lists.gnu.org/archive/html/qemu-devel/2017-06/msg05568.html
> (Yulei RFC)
> 
> Cc: Kevin Tian <kevin.tian@intel.com>
> Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
> ---
>  hw/vfio/common.c              | 5 ++++-
>  hw/vfio/migration.c           | 8 +++++---
>  include/hw/vfio/vfio-common.h | 3 ++-
>  3 files changed, 11 insertions(+), 5 deletions(-)

Thanks for this, Yan.

Kirti, I never saw an acknowledgment of this, can you confirm you've
incorporated this into your latest?  I do see we're making use of
memory_region_get_ram_addr() now.  Thanks,

Alex

 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 6f36b02..ba1a8ef 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -799,6 +799,7 @@ static void vfio_listerner_log_sync(MemoryListener *listener,
>          MemoryRegionSection *section)
>  {
>      uint64_t start_addr, size, pfn_count;
> +    uint64_t block_start;
>      VFIOGroup *group;
>      VFIODevice *vbasedev;
>  
> @@ -819,11 +820,13 @@ static void vfio_listerner_log_sync(MemoryListener *listener,
>      start_addr = TARGET_PAGE_ALIGN(section->offset_within_address_space);
>      size = int128_get64(section->size);
>      pfn_count = size >> TARGET_PAGE_BITS;
> +    block_start = TARGET_PAGE_ALIGN(section->offset_within_region +
> +                             memory_region_get_ram_addr(section->mr));
>  
>      QLIST_FOREACH(group, &vfio_group_list, next) {
>          QLIST_FOREACH(vbasedev, &group->device_list, next) {
>              vfio_get_dirty_page_list(vbasedev, start_addr >> TARGET_PAGE_BITS,
> -                                     pfn_count, TARGET_PAGE_SIZE);
> +                                     pfn_count, TARGET_PAGE_SIZE, block_start);
>          }
>      }
>  }
> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
> index 640bea1..a19b957 100644
> --- a/hw/vfio/migration.c
> +++ b/hw/vfio/migration.c
> @@ -279,7 +279,8 @@ static int vfio_load_device_config_state(QEMUFile *f, void *opaque)
>  void vfio_get_dirty_page_list(VFIODevice *vbasedev,
>                                uint64_t start_pfn,
>                                uint64_t pfn_count,
> -                              uint64_t page_size)
> +                              uint64_t page_size,
> +                              uint64_t block_start)
>  {
>      VFIOMigration *migration = vbasedev->migration;
>      VFIORegion *region = &migration->region;
> @@ -293,6 +294,7 @@ void vfio_get_dirty_page_list(VFIODevice *vbasedev,
>      while (total_pfns > 0) {
>          uint64_t bitmap_size, data_offset = 0;
>          uint64_t start = start_pfn + count;
> +        uint64_t block_start_seg = block_start + count * page_size;
>          void *buf = NULL;
>          bool buffer_mmaped = false;
>  
> @@ -341,7 +343,7 @@ void vfio_get_dirty_page_list(VFIODevice *vbasedev,
>              break;
>          } else if (copied_pfns == VFIO_DEVICE_DIRTY_PFNS_ALL) {
>              /* Mark all pages dirty for this range */
> -            cpu_physical_memory_set_dirty_range(start * page_size,
> +            cpu_physical_memory_set_dirty_range(block_start_seg,
>                                                  total_pfns * page_size,
>                                                  DIRTY_MEMORY_MIGRATION);
>              break;
> @@ -382,7 +384,7 @@ void vfio_get_dirty_page_list(VFIODevice *vbasedev,
>          }
>  
>          cpu_physical_memory_set_dirty_lebitmap((unsigned long *)buf,
> -                                               start * page_size,
> +                                               block_start_seg,
>                                                 copied_pfns);
>          count      += copied_pfns;
>          total_pfns -= copied_pfns;
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index 41ff5eb..6d868fa 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -220,6 +220,7 @@ int vfio_spapr_remove_window(VFIOContainer *container,
>  int vfio_migration_probe(VFIODevice *vbasedev, Error **errp);
>  void vfio_migration_finalize(VFIODevice *vbasedev);
>  void vfio_get_dirty_page_list(VFIODevice *vbasedev, uint64_t start_pfn,
> -                               uint64_t pfn_count, uint64_t page_size);
> +                               uint64_t pfn_count, uint64_t page_size,
> +                               uint64_t block_start);
>  
>  #endif /* HW_VFIO_VFIO_COMMON_H */