On 11/08/2017 08:46, Wanpeng Li wrote:
> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
>
> Commit c016004494b0 (KVM: x86: Avoid guest page table walk when gpa_available
> is set) avoids the page table walk when cr2 has already contained a valid GPA.
> However, that is not the truth if ept == 0 and shadow page table is used. In
> this scenario cr2 can just contains a valid GVA. The commit results in guest
> stuck during boot due to read/write emulation against GVA instead of GPA of
> the guest.
>
> This patch fixes it by setting the gpa_available flag under direct mode.
>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Cc: Brijesh Singh <brijesh.singh@xxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 849312d..4780348 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -3791,8 +3791,11 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
>
> if (need_unprotect && kvm_event_needs_reinjection(vcpu))
> kvm_mmu_unprotect_page_virt(vcpu, fault_address);
> - vcpu->arch.gpa_available = true;
> - vcpu->arch.gpa_val = fault_address;
> + /* With shadow page tables, cr2 could contain a GVA, not a GPA */
A GVA or a nested GPA, more precisely.
> + if (vcpu->arch.mmu.direct_map) {
> + vcpu->arch.gpa_available = true;
> + vcpu->arch.gpa_val = fault_address;
> + }
> r = kvm_mmu_page_fault(vcpu, fault_address, error_code, insn,
> insn_len);
> break;
>
Also not enough, we need
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 5fd7ecbf7284..283e94de3853 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6393,7 +6393,7 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
error_code |= (exit_qualification & 0x100) != 0 ?
PFERR_GUEST_FINAL_MASK : PFERR_GUEST_PAGE_MASK;
- vcpu->arch.gpa_available = true;
+ vcpu->arch.gpa_available = !is_guest_mode(vcpu);
vcpu->arch.gpa_val = gpa;
vcpu->arch.exit_qualification = exit_qualification;
@@ -6412,7 +6412,7 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu)
}
ret = handle_mmio_page_fault(vcpu, gpa, true);
- vcpu->arch.gpa_available = true;
+ vcpu->arch.gpa_available = !is_guest_mode(vcpu);
vcpu->arch.gpa_val = gpa;
if (likely(ret == RET_MMIO_PF_EMULATE))
return x86_emulate_instruction(vcpu, gpa, 0, NULL, 0) ==
Paolo
