On 08/08/2014 02:32 AM, David Matlack wrote: > The following events can lead to an incorrect KVM_EXIT_MMIO bubbling > up to userspace: > > (1) Guest accesses gpa X without a memory slot. The gfn is cached in > struct kvm_vcpu_arch (mmio_gfn). On Intel EPT-enabled hosts, KVM sets > the SPTE write-execute-noread so that future accesses cause > EPT_MISCONFIGs. > > (2) Host userspace creates a memory slot via KVM_SET_USER_MEMORY_REGION > covering the page just accessed. > > (3) Guest attempts to read or write to gpa X again. On Intel, this > generates an EPT_MISCONFIG. The memory slot generation number that > was incremented in (2) would normally take care of this but we fast > path mmio faults through quickly_check_mmio_pf(), which only checks > the per-vcpu mmio cache. Since we hit the cache, KVM passes a > KVM_EXIT_MMIO up to userspace. > > This patch fixes the issue by using the memslot generation number > to validate the mmio cache. > > Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx> > --- > The patch diff is rather large because I had to pull some code out > of x86.h and mmu.c and into mmu.h. The main change is adding the > memslot generation in vcpu_cach_mmio_info() and then validating > that slot in vcpu_match_mmio_*(). Why not just move vcpu_cach_mmio_info() into mmu.c where is the only place vcpu_cach_mmio_info is called. :) BTW, i will post a patch to fix the generation-number issue soon. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
