Hi Eric,
> From: Eric Auger <eric.au...@redhat.com>
> Sent: Saturday, March 21, 2020 12:58 AM
> To: eric.auger....@gmail.com; eric.au...@redhat.com; qemu-devel@nongnu.org;
> Subject: [RFC v6 09/24] vfio: Force nested if iommu requires it
>
> In case we detect the address space is translated by
> a virtual IOMMU which requires HW nested paging to
> integrate with VFIO, let's set up the container with
> the VFIO_TYPE1_NESTING_IOMMU iommu_type.
>
> Signed-off-by: Eric Auger <eric.au...@redhat.com>
>
> ---
>
> v4 -> v5:
> - fail immediatly if nested is wanted but not supported
>
> v2 -> v3:
> - add "nested only is selected if requested by @force_nested"
> comment in this patch
> ---
> hw/vfio/common.c | 36 ++++++++++++++++++++++++++++--------
> 1 file changed, 28 insertions(+), 8 deletions(-)
>
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index 0b3593b3c0..ac417b5dbd 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -1155,27 +1155,38 @@ static void vfio_put_address_space(VFIOAddressSpace
> *space)
> * vfio_get_iommu_type - selects the richest iommu_type (v2 first)
> */
> static int vfio_get_iommu_type(VFIOContainer *container,
> + bool want_nested,
> Error **errp)
> {
> - int iommu_types[] = { VFIO_TYPE1v2_IOMMU, VFIO_TYPE1_IOMMU,
> + int iommu_types[] = { VFIO_TYPE1_NESTING_IOMMU,
> + VFIO_TYPE1v2_IOMMU, VFIO_TYPE1_IOMMU,
> VFIO_SPAPR_TCE_v2_IOMMU, VFIO_SPAPR_TCE_IOMMU };
> - int i;
> + int i, ret = -EINVAL;
>
> for (i = 0; i < ARRAY_SIZE(iommu_types); i++) {
> if (ioctl(container->fd, VFIO_CHECK_EXTENSION, iommu_types[i])) {
> - return iommu_types[i];
> + if (iommu_types[i] == VFIO_TYPE1_NESTING_IOMMU && !want_nested) {
> + continue;
> + }
> + ret = iommu_types[i];
> + break;
> }
> }
> - error_setg(errp, "No available IOMMU models");
> - return -EINVAL;
> + if (ret < 0) {
> + error_setg(errp, "No available IOMMU models");
> + } else if (want_nested && ret != VFIO_TYPE1_NESTING_IOMMU) {
> + error_setg(errp, "Nested mode requested but not supported");
> + ret = -EINVAL;
> + }
> + return ret;
> }
>
> static int vfio_init_container(VFIOContainer *container, int group_fd,
> - Error **errp)
> + bool want_nested, Error **errp)
> {
> int iommu_type, ret;
>
> - iommu_type = vfio_get_iommu_type(container, errp);
> + iommu_type = vfio_get_iommu_type(container, want_nested, errp);
> if (iommu_type < 0) {
> return iommu_type;
> }
> @@ -1211,6 +1222,14 @@ static int vfio_connect_container(VFIOGroup *group,
> AddressSpace *as,
> VFIOContainer *container;
> int ret, fd;
> VFIOAddressSpace *space;
> + IOMMUMemoryRegion *iommu_mr;
> + bool nested = false;
> +
> + if (as != &address_space_memory && memory_region_is_iommu(as->root)) {
I tried on my side. For virtual VT-d, it doesn't work as in intel_iommu,
we have a dynamic switch mechanism. Thus that, the
memory_region_is_iommu(as->root) won't return true as expected. I'm afraid
it doesn't work for virtual VT-d. So firstly, I'm wondering if
as != &address_space_memory is enough. Secondly, I'm considering if it is
good to let vfio_get_group() caller to provide a hint whether vIOMMU is
exposed. e.g. vfio_realize() in vfio/pci.c could figure out whether vIOMMU
is set easily. Thoughts?
Regards,
Yi Liu
