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Message-ID: <CALzav=f_DYTSUeX7a9HRMoY1JMb1bYJgd_7h-08=fDPZQOVxFg@mail.gmail.com> Date: Thu, 14 Aug 2014 09:25:49 -0700 From: David Matlack <dmatlack@...gle.com> To: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com> Cc: Gleb Natapov <gleb@...nel.org>, Avi Kivity <avi.kivity@...il.com>, mtosatti@...hat.com, Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org, kvm@...r.kernel.org, stable@...r.kernel.org Subject: Re: [PATCH 2/2] kvm: x86: fix stale mmio cache bug On Thu, Aug 14, 2014 at 12:01 AM, Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com> wrote: > From: David Matlack <dmatlack@...gle.com> > > 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. > > [ xiaoguangrong: adjust the code to make it simpler for stable-tree fix. ] The adjustments look good. Thanks! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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