Re: [PATCH QEMU v25 11/17] vfio: Get migration capability flags for container

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

On Thu, 25 Jun 2020 19:39:08 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> On 6/25/2020 12:25 AM, Alex Williamson wrote:
> > On Sun, 21 Jun 2020 01:51:20 +0530
> > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> >   
> >> Added helper functions to get IOMMU info capability chain.
> >> Added function to get migration capability information from that
> >> capability chain for IOMMU container.
> >>
> >> Similar change was proposed earlier:
> >> https://lists.gnu.org/archive/html/qemu-devel/2018-05/msg03759.html
> >>
> >> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> >> Cc: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> >> Cc: Eric Auger <eric.auger@redhat.com>
> >> ---
> >>   hw/vfio/common.c              | 91 +++++++++++++++++++++++++++++++++++++++----
> >>   include/hw/vfio/vfio-common.h |  3 ++
> >>   2 files changed, 86 insertions(+), 8 deletions(-)
> >>
> >> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> >> index 90e9a854d82c..e0d3d4585a65 100644
> >> --- a/hw/vfio/common.c
> >> +++ b/hw/vfio/common.c
> >> @@ -1229,6 +1229,75 @@ static int vfio_init_container(VFIOContainer *container, int group_fd,
> >>       return 0;
> >>   }
> >>   
> >> +static int vfio_get_iommu_info(VFIOContainer *container,
> >> +                               struct vfio_iommu_type1_info **info)
> >> +{
> >> +
> >> +    size_t argsz = sizeof(struct vfio_iommu_type1_info);
> >> +
> >> +    *info = g_new0(struct vfio_iommu_type1_info, 1);
> >> +again:
> >> +    (*info)->argsz = argsz;
> >> +
> >> +    if (ioctl(container->fd, VFIO_IOMMU_GET_INFO, *info)) {
> >> +        g_free(*info);
> >> +        *info = NULL;
> >> +        return -errno;
> >> +    }
> >> +
> >> +    if (((*info)->argsz > argsz)) {
> >> +        argsz = (*info)->argsz;
> >> +        *info = g_realloc(*info, argsz);
> >> +        goto again;
> >> +    }
> >> +
> >> +    return 0;
> >> +}
> >> +
> >> +static struct vfio_info_cap_header *
> >> +vfio_get_iommu_info_cap(struct vfio_iommu_type1_info *info, uint16_t id)
> >> +{
> >> +    struct vfio_info_cap_header *hdr;
> >> +    void *ptr = info;
> >> +
> >> +    if (!(info->flags & VFIO_IOMMU_INFO_CAPS)) {
> >> +        return NULL;
> >> +    }
> >> +
> >> +    for (hdr = ptr + info->cap_offset; hdr != ptr; hdr = ptr + hdr->next) {
> >> +        if (hdr->id == id) {
> >> +            return hdr;
> >> +        }
> >> +    }
> >> +
> >> +    return NULL;
> >> +}
> >> +
> >> +static void vfio_get_iommu_info_migration(VFIOContainer *container,
> >> +                                         struct vfio_iommu_type1_info *info)
> >> +{
> >> +    struct vfio_info_cap_header *hdr;
> >> +    struct vfio_iommu_type1_info_cap_migration *cap_mig;
> >> +
> >> +    hdr = vfio_get_iommu_info_cap(info, VFIO_IOMMU_TYPE1_INFO_CAP_MIGRATION);
> >> +    if (!hdr) {
> >> +        return;
> >> +    }
> >> +
> >> +    cap_mig = container_of(hdr, struct vfio_iommu_type1_info_cap_migration,
> >> +                            header);
> >> +
> >> +    container->dirty_pages_supported = true;
> >> +    container->max_dirty_bitmap_size = cap_mig->max_dirty_bitmap_size;
> >> +    container->dirty_pgsizes = cap_mig->pgsize_bitmap;
> >> +
> >> +    /*
> >> +     * cpu_physical_memory_set_dirty_lebitmap() expects pages in bitmap of
> >> +     * TARGET_PAGE_SIZE to mark those dirty.
> >> +     */
> >> +    assert(container->dirty_pgsizes & TARGET_PAGE_SIZE);  
> > 
> > Why assert versus simply not support dirty page tracking and therefore
> > migration of contained devices?
> >   
> 
> Ok, that can be done.
> 
> >> +}
> >> +
> >>   static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
> >>                                     Error **errp)
> >>   {
> >> @@ -1293,6 +1362,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
> >>       container->space = space;
> >>       container->fd = fd;
> >>       container->error = NULL;
> >> +    container->dirty_pages_supported = false;
> >>       QLIST_INIT(&container->giommu_list);
> >>       QLIST_INIT(&container->hostwin_list);
> >>   
> >> @@ -1305,7 +1375,7 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
> >>       case VFIO_TYPE1v2_IOMMU:
> >>       case VFIO_TYPE1_IOMMU:
> >>       {
> >> -        struct vfio_iommu_type1_info info;
> >> +        struct vfio_iommu_type1_info *info;
> >>   
> >>           /*
> >>            * FIXME: This assumes that a Type1 IOMMU can map any 64-bit
> >> @@ -1314,15 +1384,20 @@ static int vfio_connect_container(VFIOGroup *group, AddressSpace *as,
> >>            * existing Type1 IOMMUs generally support any IOVA we're
> >>            * going to actually try in practice.
> >>            */
> >> -        info.argsz = sizeof(info);
> >> -        ret = ioctl(fd, VFIO_IOMMU_GET_INFO, &info);
> >> -        /* Ignore errors */
> >> -        if (ret || !(info.flags & VFIO_IOMMU_INFO_PGSIZES)) {
> >> +        ret = vfio_get_iommu_info(container, &info);
> >> +        if (ret) {
> >> +                goto free_container_exit;  
> > 
> > This was previously not fatal, why is it now?  Thanks,
> >   
> 
> Cornelia asked same question.
> Then what should be the action if ioctl fails? Disable migration?

Yes, new features shouldn't impose constraints not previously present.
Thanks,

Alex
   
> >> +        }
> >> +
> >> +        if (!(info->flags & VFIO_IOMMU_INFO_PGSIZES)) {
> >>               /* Assume 4k IOVA page size */
> >> -            info.iova_pgsizes = 4096;
> >> +            info->iova_pgsizes = 4096;
> >>           }
> >> -        vfio_host_win_add(container, 0, (hwaddr)-1, info.iova_pgsizes);
> >> -        container->pgsizes = info.iova_pgsizes;
> >> +        vfio_host_win_add(container, 0, (hwaddr)-1, info->iova_pgsizes);
> >> +        container->pgsizes = info->iova_pgsizes;
> >> +
> >> +        vfio_get_iommu_info_migration(container, info);
> >> +        g_free(info);
> >>           break;
> >>       }
> >>       case VFIO_SPAPR_TCE_v2_IOMMU:
> >> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> >> index c78033e4149d..5a57a78ec517 100644
> >> --- a/include/hw/vfio/vfio-common.h
> >> +++ b/include/hw/vfio/vfio-common.h
> >> @@ -79,6 +79,9 @@ typedef struct VFIOContainer {
> >>       unsigned iommu_type;
> >>       Error *error;
> >>       bool initialized;
> >> +    bool dirty_pages_supported;
> >> +    uint64_t dirty_pgsizes;
> >> +    uint64_t max_dirty_bitmap_size;
> >>       unsigned long pgsizes;
> >>       QLIST_HEAD(, VFIOGuestIOMMU) giommu_list;
> >>       QLIST_HEAD(, VFIOHostDMAWindow) hostwin_list;  
> >   
>