Re: [PATCH v4 08/14] vfio/common: Record DMA mapped IOVA ranges

[Alex Williamson]

On Tue,  7 Mar 2023 02:02:52 +0000
Joao Martins <joao.m.martins@oracle.com> wrote:

> According to the device DMA logging uAPI, IOVA ranges to be logged by
> the device must be provided all at once upon DMA logging start.
> 
> As preparation for the following patches which will add device dirty
> page tracking, keep a record of all DMA mapped IOVA ranges so later they
> can be used for DMA logging start.
> 
> Signed-off-by: Avihai Horon <avihaih@nvidia.com>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> ---
>  hw/vfio/common.c              | 76 +++++++++++++++++++++++++++++++++++
>  hw/vfio/trace-events          |  1 +
>  include/hw/vfio/vfio-common.h | 13 ++++++
>  3 files changed, 90 insertions(+)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 3a6491dbc523..a9b1fc999121 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -1334,11 +1334,87 @@ static int vfio_set_dirty_page_tracking(VFIOContainer 
> *container, bool start)
>      return ret;
>  }
>  
> +static void vfio_dirty_tracking_update(MemoryListener *listener,
> +                                       MemoryRegionSection *section)
> +{
> +    VFIODirtyRanges *dirty = container_of(listener, VFIODirtyRanges, 
> listener);
> +    VFIODirtyTrackingRange *range = &dirty->ranges;
> +    hwaddr max32 = UINT32_MAX - 1ULL;

The -1 is wrong here, UINT32_MAX is (2^32 - 1)

> +    hwaddr iova, end;
> +
> +    if (!vfio_listener_valid_section(section) ||
> +        !vfio_get_section_iova_range(dirty->container, section,
> +                                     &iova, &end, NULL)) {
> +        return;
> +    }
> +
> +    /*
> +     * The address space passed to the dirty tracker is reduced to two 
> ranges:
> +     * one for 32-bit DMA ranges, and another one for 64-bit DMA ranges.
> +     * The underlying reports of dirty will query a sub-interval of each of
> +     * these ranges.
> +     *
> +     * The purpose of the dual range handling is to handle known cases of big
> +     * holes in the address space, like the x86 AMD 1T hole. The alternative
> +     * would be an IOVATree but that has a much bigger runtime overhead and
> +     * unnecessary complexity.
> +     */
> +    if (iova < max32 && end <= max32) {

Nit, the first test is redundant, iova is necessarily less than end.

> +        if (range->min32 > iova) {
> +            range->min32 = iova;
> +        }
> +        if (range->max32 < end) {
> +            range->max32 = end;
> +        }
> +        trace_vfio_device_dirty_tracking_update(iova, end,
> +                                    range->min32, range->max32);
> +    } else {
> +        if (!range->min64 || range->min64 > iova) {

The first test should be removed, we're initializing min64 to a
non-zero value now, so if it's zero it's been set and we can't
de-prioritize that set value.

> +            range->min64 = iova;
> +        }
> +        if (range->max64 < end) {
> +            range->max64 = end;
> +        }
> +        trace_vfio_device_dirty_tracking_update(iova, end,
> +                                    range->min64, range->max64);
> +    }
> +
> +    return;
> +}
> +
> +static const MemoryListener vfio_dirty_tracking_listener = {
> +    .name = "vfio-tracking",
> +    .region_add = vfio_dirty_tracking_update,
> +};
> +
> +static void vfio_dirty_tracking_init(VFIOContainer *container,
> +                                     VFIODirtyRanges *dirty)
> +{
> +    memset(dirty, 0, sizeof(*dirty));
> +    dirty->ranges.min32 = UINT32_MAX;
> +    dirty->ranges.min64 = UINT64_MAX;
> +    dirty->listener = vfio_dirty_tracking_listener;
> +    dirty->container = container;
> +

I was actually thinking the caller would just pass
VFIODirtyTrackingRange and VFIODirtyRanges would be allocated on the
stack here, perhaps both are defined private to this file, but this
works and we can refine later if we so decide.  Thanks,

Alex


> +    memory_listener_register(&dirty->listener,
> +                             container->space->as);
> +
> +    /*
> +     * The memory listener is synchronous, and used to calculate the range
> +     * to dirty tracking. Unregister it after we are done as we are not
> +     * interested in any follow-up updates.
> +     */
> +    memory_listener_unregister(&dirty->listener);
> +}
> +
>  static void vfio_listener_log_global_start(MemoryListener *listener)
>  {
>      VFIOContainer *container = container_of(listener, VFIOContainer, 
> listener);
> +    VFIODirtyRanges dirty;
>      int ret;
>  
> +    vfio_dirty_tracking_init(container, &dirty);
> +
>      ret = vfio_set_dirty_page_tracking(container, true);
>      if (ret) {
>          vfio_set_migration_error(ret);
> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
> index 669d9fe07cd9..d97a6de17921 100644
> --- a/hw/vfio/trace-events
> +++ b/hw/vfio/trace-events
> @@ -104,6 +104,7 @@ vfio_known_safe_misalignment(const char *name, uint64_t 
> iova, uint64_t offset_wi
>  vfio_listener_region_add_no_dma_map(const char *name, uint64_t iova, 
> uint64_t size, uint64_t page_size) "Region \"%s\" 0x%"PRIx64" 
> size=0x%"PRIx64" is not aligned to 0x%"PRIx64" and cannot be mapped for DMA"
>  vfio_listener_region_del_skip(uint64_t start, uint64_t end) "SKIPPING 
> region_del 0x%"PRIx64" - 0x%"PRIx64
>  vfio_listener_region_del(uint64_t start, uint64_t end) "region_del 
> 0x%"PRIx64" - 0x%"PRIx64
> +vfio_device_dirty_tracking_update(uint64_t start, uint64_t end, uint64_t 
> min, uint64_t max) "section 0x%"PRIx64" - 0x%"PRIx64" -> update [0x%"PRIx64" 
> - 0x%"PRIx64"]"
>  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"
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index 87524c64a443..0f84136cceb5 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -96,6 +96,19 @@ typedef struct VFIOContainer {
>      QLIST_ENTRY(VFIOContainer) next;
>  } VFIOContainer;
>  
> +typedef struct VFIODirtyTrackingRange {
> +    hwaddr min32;
> +    hwaddr max32;
> +    hwaddr min64;
> +    hwaddr max64;
> +} VFIODirtyTrackingRange;
> +
> +typedef struct VFIODirtyRanges {
> +    VFIOContainer *container;
> +    VFIODirtyTrackingRange ranges;
> +    MemoryListener listener;
> +} VFIODirtyRanges;
> +
>  typedef struct VFIOGuestIOMMU {
>      VFIOContainer *container;
>      IOMMUMemoryRegion *iommu_mr;