On Wed, Jul 28, 2021 at 10:57:30AM +0100, Marc Zyngier wrote: > On Tue, 27 Jul 2021 19:11:08 +0100, > Will Deacon <w...@kernel.org> wrote: > > On Thu, Jul 15, 2021 at 05:31:47PM +0100, Marc Zyngier wrote: > > > +bool kvm_install_ioguard_page(struct kvm_vcpu *vcpu, gpa_t ipa) > > > +{ > > > + struct kvm_mmu_memory_cache *memcache; > > > + struct kvm_memory_slot *memslot; > > > + int ret, idx; > > > + > > > + if (!test_bit(KVM_ARCH_FLAG_MMIO_GUARD, &vcpu->kvm->arch.flags)) > > > + return false; > > > + > > > + /* Must be page-aligned */ > > > + if (ipa & ~PAGE_MASK) > > > + return false; > > > + > > > + /* > > > + * The page cannot be in a memslot. At some point, this will > > > + * have to deal with device mappings though. > > > + */ > > > + idx = srcu_read_lock(&vcpu->kvm->srcu); > > > + memslot = gfn_to_memslot(vcpu->kvm, ipa >> PAGE_SHIFT); > > > + srcu_read_unlock(&vcpu->kvm->srcu, idx); > > > > What does this memslot check achieve? A new memslot could be added after > > you've checked, no? > > If you start allowing S2 annotations to coexist with potential memory > mappings, you're in for trouble. The faulting logic will happily > overwrite the annotation, and that's probably not what you want.
I don't disagree, but the check above appears to be racy. > As for new (or moving) memslots, I guess they should be checked > against existing annotations. Something like that, but the devil is in the details as it will need to synchronize with this check somehow. Will _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm