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SubjectRe: [PATCH v2] KVM: X86: Fix CR3 reserve bits

----- kernellwp@gmail.com wrote:

> From: Wanpeng Li <wanpengli@tencent.com>
>
> MSB of CR3 is a reserved bit if the PCIDE bit is not set in CR4.
> It should be checked when PCIDE bit is not set, however commit
> 'd1cd3ce900441 ("KVM: MMU: check guest CR3 reserved bits based on
> its physical address width")' removes the bit 63 checking
> unconditionally. This patch fixes it by checking bit 63 of CR3
> when PCIDE bit is not set in CR4.
>
> Fixes: d1cd3ce900441 (KVM: MMU: check guest CR3 reserved bits based on
> its physical address width)
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Junaid Shahid <junaids@google.com>
> Cc: Liran Alon <liran.alon@oracle.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
> v1 -> v2:
> * remove CR3_PCID_INVD in rsvd when PCIDE is 1 instead of
> removing CR3_PCID_INVD in new_value
>
> arch/x86/kvm/emulate.c | 4 +++-
> arch/x86/kvm/x86.c | 2 +-
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index b3705ae..143b7ae 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -4189,7 +4189,9 @@ static int check_cr_write(struct
> x86_emulate_ctxt *ctxt)
> maxphyaddr = eax & 0xff;
> else
> maxphyaddr = 36;
> - rsvd = rsvd_bits(maxphyaddr, 62);
> + rsvd = rsvd_bits(maxphyaddr, 63);
> + if (ctxt->ops->get_cr(ctxt, 4) & X86_CR4_PCIDE)
> + rsvd &= ~CR3_PCID_INVD;
> }
>
> if (new_val & rsvd)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 87e4805..9a90668 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -863,7 +863,7 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned
> long cr3)
> }
>
> if (is_long_mode(vcpu) &&
> - (cr3 & rsvd_bits(cpuid_maxphyaddr(vcpu), 62)))
> + (cr3 & rsvd_bits(cpuid_maxphyaddr(vcpu), 63)))
> return 1;
> else if (is_pae(vcpu) && is_paging(vcpu) &&
> !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
> --
> 2.7.4

Reviewed-by: Liran Alon <liran.alon@oracle.com>

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