Hi Paolo and Radim
Any comments on this patch, I could not find it in 4.13-2 branch.
Please let me know if you want to fix something, or want me to
refresh and resend the patch.
- Brijesh
On 05/19/2017 10:12 AM, Brijesh Singh wrote:
> From: Brijesh Singh <[email protected]>
>
> On AMD hardware when a guest causes a NPF which requires emulation,
> the vcpu->arch.gpa_available flag is set to indicate that cr2 contains
> a valid GPA.
>
> Currently, emulator_read_write_onepage() makes use of gpa_available flag
> to avoid a guest page walk for a known MMIO regions. Lets not limit
> the gpa_available optimization to just MMIO region. The patch extends
> the check to avoid page walk whenever gpa_available flag is set.
>
> Signed-off-by: Brijesh Singh <[email protected]>
> ---
> v1: http://marc.info/?l=kvm&m=149304930814202&w=2
>
> Changes in v2:
> - move gpa_val setting in pf_interception
>
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/svm.c | 4 ++++
> arch/x86/kvm/x86.c | 14 +++++++-------
> 3 files changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 695605e..cc87e00 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -678,6 +678,7 @@ struct kvm_vcpu_arch {
>
> /* GPA available (AMD only) */
> bool gpa_available;
> + gpa_t gpa_val;
> };
>
> struct kvm_lpage_info {
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index c27ac69..27fb563 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2070,9 +2070,13 @@ static void svm_set_dr7(struct kvm_vcpu *vcpu, unsigned long value)
> static int pf_interception(struct vcpu_svm *svm)
> {
> u64 fault_address = svm->vmcb->control.exit_info_2;
> + struct kvm_vcpu *vcpu = &svm->vcpu;
> u64 error_code;
> int r = 1;
>
> + /* On #NPF, exit_info_2 contains a valid GPA */
> + vcpu->arch.gpa_val = fault_address;
> +
> switch (svm->apf_reason) {
> default:
> error_code = svm->vmcb->control.exit_info_1;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index b54125b..d2d88ed 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4634,16 +4634,16 @@ static int emulator_read_write_onepage(unsigned long addr, void *val,
> */
> if (vcpu->arch.gpa_available &&
> emulator_can_use_gpa(ctxt) &&
> - vcpu_is_mmio_gpa(vcpu, addr, exception->address, write) &&
> (addr & ~PAGE_MASK) == (exception->address & ~PAGE_MASK)) {
> - gpa = exception->address;
> - goto mmio;
> - }
> + gpa = vcpu->arch.gpa_val;
> + ret = vcpu_is_mmio_gpa(vcpu, addr, gpa, write);
> + } else {
>
> - ret = vcpu_mmio_gva_to_gpa(vcpu, addr, &gpa, exception, write);
> + ret = vcpu_mmio_gva_to_gpa(vcpu, addr, &gpa, exception, write);
>
> - if (ret < 0)
> - return X86EMUL_PROPAGATE_FAULT;
> + if (ret < 0)
> + return X86EMUL_PROPAGATE_FAULT;
> + }
>
> /* For APIC access vmexit */
> if (ret)
>
2017-07-17 16:32-0500, Brijesh Singh:
> Hi Paolo and Radim
>
> Any comments on this patch, I could not find it in 4.13-2 branch.
>
> Please let me know if you want to fix something, or want me to
> refresh and resend the patch.
Sorry, I tried it during the merge window, but it didn't pass tests on
VMX and I got distracted by other bugs before looking into the cause.
Can you reproduce the fail?
On 07/19/2017 06:19 AM, Radim Krčmář wrote:
> 2017-07-17 16:32-0500, Brijesh Singh:
>> Hi Paolo and Radim
>>
>> Any comments on this patch, I could not find it in 4.13-2 branch.
>>
>> Please let me know if you want to fix something, or want me to
>> refresh and resend the patch.
>
> Sorry, I tried it during the merge window, but it didn't pass tests on
> VMX and I got distracted by other bugs before looking into the cause.
>
> Can you reproduce the fail?
>
No worries, thanks.
I can try to reproduce it, are you running kvm-unittest or something different?
IIRC, VMX does not set the gpa_available flag hence I am wondering what did I miss
in the patch to trigger the failure. I will debug it and let you know.
-Brijesh
2017-07-19 08:35-0500, Brijesh Singh:
> On 07/19/2017 06:19 AM, Radim Krčmář wrote:
> > 2017-07-17 16:32-0500, Brijesh Singh:
> > > Hi Paolo and Radim
> > >
> > > Any comments on this patch, I could not find it in 4.13-2 branch.
> > >
> > > Please let me know if you want to fix something, or want me to
> > > refresh and resend the patch.
> >
> > Sorry, I tried it during the merge window, but it didn't pass tests on
> > VMX and I got distracted by other bugs before looking into the cause.
> >
> > Can you reproduce the fail?
> >
>
> No worries, thanks.
>
> I can try to reproduce it, are you running kvm-unittest or something different?
I noticed that a linux guest hung in early boot, but at least (io)apic
kvm-unit-tests failed as well, IIRC.
> IIRC, VMX does not set the gpa_available flag hence I am wondering what did I miss
> in the patch to trigger the failure. I will debug it and let you know.
It does now, in ept_violation and ept_misconfig,
thanks.
Hi Radim,
On 07/20/2017 02:43 AM, Radim Krčmář wrote:
> 2017-07-19 08:35-0500, Brijesh Singh:
>> On 07/19/2017 06:19 AM, Radim Krčmář wrote:
>>> 2017-07-17 16:32-0500, Brijesh Singh:
>>>> Hi Paolo and Radim
>>>>
>>>> Any comments on this patch, I could not find it in 4.13-2 branch.
>>>>
>>>> Please let me know if you want to fix something, or want me to
>>>> refresh and resend the patch.
>>>
>>> Sorry, I tried it during the merge window, but it didn't pass tests on
>>> VMX and I got distracted by other bugs before looking into the cause.
>>>
>>> Can you reproduce the fail?
>>>
>>
>> No worries, thanks.
>>
>> I can try to reproduce it, are you running kvm-unittest or something different?
>
> I noticed that a linux guest hung in early boot, but at least (io)apic
> kvm-unit-tests failed as well, IIRC.
>
>> IIRC, VMX does not set the gpa_available flag hence I am wondering what did I miss
>> in the patch to trigger the failure. I will debug it and let you know.
>
> It does now, in ept_violation and ept_misconfig,
>
I am able to reproduce the issue on VMX, Sorry it took a bit longer to verify
it.
I was not aware that VMX is also making use of gpa_available flag hence I missed
updating the vmx.c to set the gpa_val. After applying the below small patch I am
able to boot the guest on Intel Xeon E5-2665.
Additionally, there was one issue in current patch pointed by Paolo [1]. If patch
was using vcpu->arch.gpa_val check as pointed by Paolo then on VMX we will silently
fallback to guest page table walk (even when gpa_available is set). I guess since I
have testing my code on SVM platform hence never caught the error. I will soon send
updated patch.
[1] http://marc.info/?l=kvm&m=150116338725964&w=2
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index b5e0b02..9309fbb 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6309,6 +6309,7 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
? PFERR_PRESENT_MASK : 0;
vcpu->arch.gpa_available = true;
+ vcpu->arch.gpa_val = gpa;
vcpu->arch.exit_qualification = exit_qualification;
return kvm_mmu_page_fault(vcpu, gpa, error_code, NULL, 0);
@@ -6326,6 +6327,7 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu)
}
ret = handle_mmio_page_fault(vcpu, gpa, true);
+ vcpu->arch.gpa_val = gpa;
vcpu->arch.gpa_available = true;
if (likely(ret == RET_MMIO_PF_EMULATE))
return x86_emulate_instruction(vcpu, gpa, 0, NULL, 0) ==