Hi Peter,
On 9/13/18 9:55 AM, Peter Xu wrote:
> There are two callers for vtd_sync_shadow_page_table_range(), one
> provided a valid context entry and one not. Move that fetching
> operation into the caller vtd_sync_shadow_page_table() where we need to
> fetch the context entry.
>
> Meanwhile, we should handle VTD_FR_CONTEXT_ENTRY_P properly when
> synchronizing shadow page tables. Having invalid context entry there is
> perfectly valid when we move a device out of an existing domain. When
> that happens, instead of posting an error we invalidate the whole region.
>
> Without this patch, QEMU will crash if we do these steps:
>
> (1) start QEMU with VT-d IOMMU and two 10G NICs (ixgbe)
> (2) bind the NICs with vfio-pci in the guest
> (3) start testpmd with the NICs applied
> (4) stop testpmd
> (5) rebind the NIC back to ixgbe kernel driver
>
> The patch should fix it.
>
> Reported-by: Pei Zhang <pezh...@redhat.com>
> Tested-by: Pei Zhang <pezh...@redhat.com>
> CC: Pei Zhang <pezh...@redhat.com>
> CC: Alex Williamson <alex.william...@redhat.com>
> CC: Jason Wang <jasow...@redhat.com>
> CC: Maxime Coquelin <maxime.coque...@redhat.com>
> CC: Michael S. Tsirkin <m...@redhat.com>
> CC: QEMU Stable <qemu-sta...@nongnu.org>
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1627272
> Signed-off-by: Peter Xu <pet...@redhat.com>
> ---
> hw/i386/intel_iommu.c | 54 ++++++++++++++++++++++++++-----------------
> 1 file changed, 33 insertions(+), 21 deletions(-)
>
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 3dfada19a6..2509520d6f 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -37,6 +37,8 @@
> #include "kvm_i386.h"
> #include "trace.h"
>
> +static void vtd_address_space_unmap(VTDAddressSpace *as, IOMMUNotifier *n);
> +
> static void vtd_define_quad(IntelIOMMUState *s, hwaddr addr, uint64_t val,
> uint64_t wmask, uint64_t w1cmask)
> {
Comment above is outdated:
/* If context entry is NULL, we'll try to fetch it on our own. */
> @@ -1047,39 +1049,49 @@ static int
> vtd_sync_shadow_page_table_range(VTDAddressSpace *vtd_as,
> .notify_unmap = true,
> .aw = s->aw_bits,
> .as = vtd_as,
> + .domain_id = VTD_CONTEXT_ENTRY_DID(ce->hi),
> };
> - VTDContextEntry ce_cache;
> +
> + return vtd_page_walk(ce, addr, addr + size, &info);
> +}
Maybe change would gain in clarity if split into 2 patches, code
reorganization and fix on the side.
Thanks
Eric
> +
> +static int vtd_sync_shadow_page_table(VTDAddressSpace *vtd_as)
> +{
> int ret;
> + VTDContextEntry ce;
> + IOMMUNotifier *n;
>
> - if (ce) {
> - /* If the caller provided context entry, use it */
> - ce_cache = *ce;
> - } else {
> - /* If the caller didn't provide ce, try to fetch */
> - ret = vtd_dev_to_context_entry(s, pci_bus_num(vtd_as->bus),
> - vtd_as->devfn, &ce_cache);
> - if (ret) {
> + ret = vtd_dev_to_context_entry(vtd_as->iommu_state,
> + pci_bus_num(vtd_as->bus),
> + vtd_as->devfn, &ce);
> + if (ret) {
> + if (ret == -VTD_FR_CONTEXT_ENTRY_P) {
> + /*
> + * It's a valid scenario to have a context entry that is
> + * not present. For example, when a device is removed
> + * from an existing domain then the context entry will be
> + * zeroed by the guest before it was put into another
> + * domain. When this happens, instead of synchronizing
> + * the shadow pages we should invalidate all existing
> + * mappings and notify the backends.
> + */
> + IOMMU_NOTIFIER_FOREACH(n, &vtd_as->iommu) {
> + vtd_address_space_unmap(vtd_as, n);
> + }
> + } else {
> /*
> * This should not really happen, but in case it happens,
> * we just skip the sync for this time. After all we even
> * don't have the root table pointer!
> */
> error_report_once("%s: invalid context entry for bus 0x%x"
> - " devfn 0x%x",
> - __func__, pci_bus_num(vtd_as->bus),
> - vtd_as->devfn);
> - return 0;
> + " devfn 0x%x", __func__,
> + pci_bus_num(vtd_as->bus), vtd_as->devfn);
> }
> + return 0;
> }
>
> - info.domain_id = VTD_CONTEXT_ENTRY_DID(ce_cache.hi);
> -
> - return vtd_page_walk(&ce_cache, addr, addr + size, &info);
> -}
> -
> -static int vtd_sync_shadow_page_table(VTDAddressSpace *vtd_as)
> -{
> - return vtd_sync_shadow_page_table_range(vtd_as, NULL, 0, UINT64_MAX);
> + return vtd_sync_shadow_page_table_range(vtd_as, &ce, 0, UINT64_MAX);
> }
>
> /*
>
