Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [PATCH v2 02/10] KVM: x86: Clear KVM's cached guest CR3 at RESET/INIT | Date | Tue, 21 Sep 2021 15:52:29 +0200 |
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Sean Christopherson <seanjc@google.com> writes:
> Explicitly zero the guest's CR3 and mark it available+dirty at RESET/INIT. > Per Intel's SDM and AMD's APM, CR3 is zeroed at both RESET and INIT. For > RESET, this is a nop as vcpu is zero-allocated. For INIT, the bug has > likely escaped notice because no firmware/kernel puts its page tables root > at PA=0, let alone relies on INIT to get the desired CR3 for such page > tables. > > Cc: stable@vger.kernel.org > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/x86/kvm/x86.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index e77a5bf2d940..2cb38c67ed43 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -10899,6 +10899,9 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event) > kvm_set_rflags(vcpu, X86_EFLAGS_FIXED); > kvm_rip_write(vcpu, 0xfff0); > > + vcpu->arch.cr3 = 0; > + kvm_register_mark_dirty(vcpu, VCPU_EXREG_CR3);
kvm_register_mark_dirty() is redundant here as PATCH1 does
vcpu->arch.regs_avail = ~0; vcpu->arch.regs_dirty = ~0;
just a few lines above. The dependency is, however, implicit and this patch is marked for stable@ (well, PATCH1 has 8 Fixes: tags so I'd expect it to get picked by everyone too, especially by robots) and flipping two bits is cheap.
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> + > /* > * CR0.CD/NW are set on RESET, preserved on INIT. Note, some versions > * of Intel's SDM list CD/NW as being set on INIT, but they contradict
-- Vitaly
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