While for context cache entry flushing use of did 0 is indeed correct (after all upon reading the context entry the IOMMU wouldn't know any domain ID if the entry is not present, and hence a surrogate one needs to be used), for IOTLB entries the normal domain ID (from the [present] context entry) gets used. See sub-section "IOTLB" of section "Address Translation Caches" in the VT-d spec.
Signed-off-by: Jan Beulich <[email protected]> --- Luckily this is supposed to be an issue only when running on emulated IOMMUs; hardware implementations are expected to have CAP.CM=0. --- a/xen/drivers/passthrough/vtd/iommu.c +++ b/xen/drivers/passthrough/vtd/iommu.c @@ -474,17 +474,10 @@ int vtd_flush_iotlb_reg(struct vtd_iommu /* * In the non-present entry flush case, if hardware doesn't cache - * non-present entry we do nothing and if hardware cache non-present - * entry, we flush entries of domain 0 (the domain id is used to cache - * any non-present entries) + * non-present entries we do nothing. */ - if ( flush_non_present_entry ) - { - if ( !cap_caching_mode(iommu->cap) ) - return 1; - else - did = 0; - } + if ( flush_non_present_entry && !cap_caching_mode(iommu->cap) ) + return 1; /* use register invalidation */ switch ( type ) --- a/xen/drivers/passthrough/vtd/qinval.c +++ b/xen/drivers/passthrough/vtd/qinval.c @@ -362,17 +362,10 @@ static int __must_check flush_iotlb_qi(s /* * In the non-present entry flush case, if hardware doesn't cache - * non-present entry we do nothing and if hardware cache non-present - * entry, we flush entries of domain 0 (the domain id is used to cache - * any non-present entries) + * non-present entries we do nothing. */ - if ( flush_non_present_entry ) - { - if ( !cap_caching_mode(iommu->cap) ) - return 1; - else - did = 0; - } + if ( flush_non_present_entry && !cap_caching_mode(iommu->cap) ) + return 1; /* use queued invalidation */ if (cap_write_drain(iommu->cap))
