Hi Peter,
On 10/8/18 8:47 AM, Peter Xu wrote:
> 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>
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1627272
> Signed-off-by: Peter Xu <pet...@redhat.com>
> ---
> hw/i386/intel_iommu.c | 20 +++++++++++++++++++-
> 1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index d6b4f8705d..b0884e87e8 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)
> {
> @@ -1056,12 +1058,28 @@ static int vtd_sync_shadow_page_table(VTDAddressSpace
> *vtd_as)
> {
> int ret;
> VTDContextEntry ce;
> + IOMMUNotifier *n;
>
> ret = vtd_dev_to_context_entry(vtd_as->iommu_state,
> pci_bus_num(vtd_as->bus),
> vtd_as->devfn, &ce);
> if (ret) {
> - return 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);
> + }
don't you want to return here also in this case?
Thanks
Eric
> + } else {
> + return ret;
> + }
> }
>
> return vtd_sync_shadow_page_table_range(vtd_as, &ce, 0, UINT64_MAX);
>
