> From: Jan Beulich <[email protected]> > Sent: Thursday, August 19, 2021 4:06 PM > > 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]>
Reviewed-by: Kevin Tian <[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))
