* Alex Williamson (alex.william...@redhat.com) wrote:
> On Thu, 25 Jun 2020 20:31:12 +0530
> Kirti Wankhede <kwankh...@nvidia.com> wrote:
>
> > On 6/25/2020 12:26 AM, Alex Williamson wrote:
> > > On Sun, 21 Jun 2020 01:51:24 +0530
> > > Kirti Wankhede <kwankh...@nvidia.com> wrote:
> > >
> > >> With vIOMMU, IO virtual address range can get unmapped while in pre-copy
> > >> phase of migration. In that case, unmap ioctl should return pages pinned
> > >> in that range and QEMU should find its correcponding guest physical
> > >> addresses and report those dirty.
> > >>
> > >> Suggested-by: Alex Williamson <alex.william...@redhat.com>
> > >> Signed-off-by: Kirti Wankhede <kwankh...@nvidia.com>
> > >> Reviewed-by: Neo Jia <c...@nvidia.com>
> > >> ---
> > >> hw/vfio/common.c | 85
> > >> +++++++++++++++++++++++++++++++++++++++++++++++++++++---
> > >> 1 file changed, 81 insertions(+), 4 deletions(-)
> > >>
> > >> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> > >> index 0518cf228ed5..a06b8f2f66e2 100644
> > >> --- a/hw/vfio/common.c
> > >> +++ b/hw/vfio/common.c
> > >> @@ -311,11 +311,83 @@ static bool
> > >> vfio_devices_are_stopped_and_saving(void)
> > >> return true;
> > >> }
> > >>
> > >> +static bool vfio_devices_are_running_and_saving(void)
> > >> +{
> > >> + VFIOGroup *group;
> > >> + VFIODevice *vbasedev;
> > >> +
> > >> + QLIST_FOREACH(group, &vfio_group_list, next) {
> > >
> > > Same as previous, I'm curious if we should instead be looking at
> > > container granularity. It especially seems to make sense here where
> > > we're unmapping from a container, so iterating every device in every
> > > group seems excessive.
> > >
> >
> > changing it with container argument.
> >
> > >> + QLIST_FOREACH(vbasedev, &group->device_list, next) {
> > >> + if ((vbasedev->device_state & VFIO_DEVICE_STATE_SAVING) &&
> > >> + (vbasedev->device_state & VFIO_DEVICE_STATE_RUNNING)) {
> > >> + continue;
> > >> + } else {
> > >> + return false;
> > >> + }
> > >
> > > I'm also not sure about the polarity of this function, should it be if
> > > any device is _SAVING we should report the dirty bitmap? For example,
> > > what if we have a set of paried failover NICs where we intend to unplug
> > > one just prior to stopping the devices, aren't we going to lose dirtied
> > > pages with this logic that they all must be running and saving? Thanks,
> > >
> >
> > If migration is initiated, is device unplug allowed? Ideally it
> > shouldn't. If it is, then how QEMU handles data stream of device which
> > doesn't exist at destination?
>
> include/hw/qdev-core.h
> struct DeviceState {
> ...
> bool allow_unplug_during_migration;
>
> AIUI, the failover_pair_id device is likely to be a vfio-pci NIC,
> otherwise they'd simply migrate the primary NIC, so there's a very good
> chance that a user would configure a VM with a migratable mdev device
> and an failover NIC so that they have high speed networking on either
> end of the migration.
My understanding for that failover code is that happens right at the
beginning of migration while we're still in MIGRATION_STATUS_SETUP;
whether there's anything that enforces that is a different matter.
But, in that case, I don't think you'd be interested in that dirtying.
Dave
> > _SAVING flag is set during pre-copy and stop-and-copy phase. Here we
> > only want to track pages which are unmapped during pre-copy phase, i.e.
> > when vCPU are running. In case of VM suspend /saveVM, there is no
> > pre-copy phase, but ideally we shouldn't see unmaps when vCPUs are
> > stopped, right? But still for safer side, since we know exact phase, I
> > would prefer to check for _SAVING and _RUNNING flags.
>
> We can't have unmaps while vCPUs are stopped, but I think the failover
> code allows that we can be in the pre-copy phase where not all devices
> support migration. As coded here, it appears that dirty tracking of any
> unmap while in that phase is lost. Thanks,
>
> Alex
>
>
> > >> + }
> > >> + }
> > >> + return true;
> > >> +}
> > >> +
> > >> +static int vfio_dma_unmap_bitmap(VFIOContainer *container,
> > >> + hwaddr iova, ram_addr_t size,
> > >> + IOMMUTLBEntry *iotlb)
> > >> +{
> > >> + struct vfio_iommu_type1_dma_unmap *unmap;
> > >> + struct vfio_bitmap *bitmap;
> > >> + uint64_t pages = TARGET_PAGE_ALIGN(size) >> TARGET_PAGE_BITS;
> > >> + int ret;
> > >> +
> > >> + unmap = g_malloc0(sizeof(*unmap) + sizeof(*bitmap));
> > >> +
> > >> + unmap->argsz = sizeof(*unmap) + sizeof(*bitmap);
> > >> + unmap->iova = iova;
> > >> + unmap->size = size;
> > >> + unmap->flags |= VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP;
> > >> + bitmap = (struct vfio_bitmap *)&unmap->data;
> > >> +
> > >> + /*
> > >> + * cpu_physical_memory_set_dirty_lebitmap() expects pages in bitmap
> > >> of
> > >> + * TARGET_PAGE_SIZE to mark those dirty. Hence set bitmap_pgsize to
> > >> + * TARGET_PAGE_SIZE.
> > >> + */
> > >> +
> > >> + bitmap->pgsize = TARGET_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%llx",
> > >> bitmap->size);
> > >> + ret = -E2BIG;
> > >> + goto unmap_exit;
> > >> + }
> > >> +
> > >> + bitmap->data = g_try_malloc0(bitmap->size);
> > >> + if (!bitmap->data) {
> > >> + ret = -ENOMEM;
> > >> + goto unmap_exit;
> > >> + }
> > >> +
> > >> + ret = ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, unmap);
> > >> + if (!ret) {
> > >> + cpu_physical_memory_set_dirty_lebitmap((uint64_t *)bitmap->data,
> > >> + iotlb->translated_addr, pages);
> > >> + } else {
> > >> + error_report("VFIO_UNMAP_DMA with DIRTY_BITMAP : %m");
> > >> + }
> > >> +
> > >> + g_free(bitmap->data);
> > >> +unmap_exit:
> > >> + g_free(unmap);
> > >> + return ret;
> > >> +}
> > >> +
> > >> /*
> > >> * DMA - Mapping and unmapping for the "type1" IOMMU interface used on
> > >> x86
> > >> */
> > >> static int vfio_dma_unmap(VFIOContainer *container,
> > >> - hwaddr iova, ram_addr_t size)
> > >> + hwaddr iova, ram_addr_t size,
> > >> + IOMMUTLBEntry *iotlb)
> > >> {
> > >> struct vfio_iommu_type1_dma_unmap unmap = {
> > >> .argsz = sizeof(unmap),
> > >> @@ -324,6 +396,11 @@ static int vfio_dma_unmap(VFIOContainer *container,
> > >> .size = size,
> > >> };
> > >>
> > >> + if (iotlb && container->dirty_pages_supported &&
> > >> + vfio_devices_are_running_and_saving()) {
> > >> + return vfio_dma_unmap_bitmap(container, iova, size, iotlb);
> > >> + }
> > >> +
> > >> while (ioctl(container->fd, VFIO_IOMMU_UNMAP_DMA, &unmap)) {
> > >> /*
> > >> * The type1 backend has an off-by-one bug in the kernel
> > >> (71a7d3d78e3c
> > >> @@ -371,7 +448,7 @@ static int vfio_dma_map(VFIOContainer *container,
> > >> hwaddr iova,
> > >> * the VGA ROM space.
> > >> */
> > >> if (ioctl(container->fd, VFIO_IOMMU_MAP_DMA, &map) == 0 ||
> > >> - (errno == EBUSY && vfio_dma_unmap(container, iova, size) == 0 &&
> > >> + (errno == EBUSY && vfio_dma_unmap(container, iova, size, NULL)
> > >> == 0 &&
> > >> ioctl(container->fd, VFIO_IOMMU_MAP_DMA, &map) == 0)) {
> > >> return 0;
> > >> }
> > >> @@ -542,7 +619,7 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n,
> > >> IOMMUTLBEntry *iotlb)
> > >> }
> > >> }
> > >>
> > >> - ret = vfio_dma_unmap(container, iova, iotlb->addr_mask + 1);
> > >> + ret = vfio_dma_unmap(container, iova, iotlb->addr_mask + 1,
> > >> iotlb);
> > >> if (ret) {
> > >> error_report("vfio_dma_unmap(%p, 0x%"HWADDR_PRIx", "
> > >> "0x%"HWADDR_PRIx") = %d (%m)",
> > >> @@ -853,7 +930,7 @@ static void vfio_listener_region_del(MemoryListener
> > >> *listener,
> > >> }
> > >>
> > >> if (try_unmap) {
> > >> - ret = vfio_dma_unmap(container, iova, int128_get64(llsize));
> > >> + ret = vfio_dma_unmap(container, iova, int128_get64(llsize),
> > >> NULL);
> > >> if (ret) {
> > >> error_report("vfio_dma_unmap(%p, 0x%"HWADDR_PRIx", "
> > >> "0x%"HWADDR_PRIx") = %d (%m)",
> > >
> >
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
