| Message ID | 20210921000303.400537-3-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: Clean up RESET "emulation" | expand |
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 Kuznetsov <vkuznets@redhat.com> writes: > 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. Scratch that, kvm_vcpu_reset() and kvm_arch_vcpu_create() got mixed up in my head :-( > > 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
On 21/09/21 02:02, Sean Christopherson wrote: > 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); > + > /* > * 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 > Queued patches 1-2 for 5.15-rc3, thanks. Paolo
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); + /* * 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
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(+)