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SubjectRe: [PATCH 00/14] nSVM fixes and optional features
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On 14/09/21 17:48, Maxim Levitsky wrote:
> Those are few patches I was working on lately, all somewhat related
> to the two CVEs that I found recently.
>
> First 7 patches fix various minor bugs that relate to these CVEs.
>
> The rest of the patches implement various optional SVM features,
> some of which the guest could enable anyway due to incorrect
> checking of virt_ext field.
>
> Last patch is somewhat an RFC, I would like to hear your opinion
> on that.
>
> I also implemented nested TSC scaling while at it.
>
> As for other optional SVM features here is my summary of few features
> I took a look at:
>
> X86_FEATURE_DECODEASSISTS:
> this feature should make it easier
> for the L1 to emulate an instruction on MMIO access, by not
> needing to read the guest memory but rather using the instruction
> bytes that the CPU already fetched.
>
> The challenge of implementing this is that we sometimes inject
> #PF and #NPT syntenically and in those cases we must be sure
> we set the correct instruction bytes.
>
> Also this feature adds assists for MOV CR/DR, INTn, and INVLPG,
> which aren't that interesting but must be supported as well to
> expose this feature to the nested guest.
>
> X86_FEATURE_VGIF
> Might allow the L2 to run the L3 a bit faster, but due to crazy complex
> logic we already have around int_ctl and vgif probably not worth it.
>
> X86_FEATURE_VMCBCLEAN
> Should just be enabled, because otherwise L1 doesn't even attempt
> to set the clean bits. But we need to know if we can take an
> advantage of these bits first.
>
> X86_FEATURE_FLUSHBYASID
> X86_FEATURE_AVIC
> These two features would be very good to enable, but that
> would require lots of work, and will be done eventually.
>
> There are few more nested SVM features that I didn't yet had a
> chance to take a look at.
>
> Best regards,
> Maxim Levitsky
>
> Maxim Levitsky (14):
> KVM: x86: nSVM: restore int_vector in svm_clear_vintr
> KVM: x86: selftests: test simultaneous uses of V_IRQ from L1 and L0
> KVM: x86: nSVM: test eax for 4K alignment for GP errata workaround
> KVM: x86: nSVM: don't copy pause related settings
> KVM: x86: nSVM: don't copy virt_ext from vmcb12
> KVM: x86: SVM: don't set VMLOAD/VMSAVE intercepts on vCPU reset
> KVM: x86: SVM: add warning for CVE-2021-3656
> KVM: x86: SVM: add module param to control LBR virtualization
> KVM: x86: nSVM: correctly virtualize LBR msrs when L2 is running
> KVM: x86: nSVM: implement nested LBR virtualization
> KVM: x86: nSVM: implement nested VMLOAD/VMSAVE
> KVM: x86: SVM: add module param to control TSC scaling
> KVM: x86: nSVM: implement nested TSC scaling
> KVM: x86: nSVM: support PAUSE filter threshold and count
>
> arch/x86/kvm/svm/nested.c | 105 +++++++--
> arch/x86/kvm/svm/svm.c | 218 +++++++++++++++---
> arch/x86/kvm/svm/svm.h | 20 +-
> arch/x86/kvm/vmx/vmx.c | 1 +
> arch/x86/kvm/x86.c | 1 +
> tools/testing/selftests/kvm/.gitignore | 1 +
> tools/testing/selftests/kvm/Makefile | 1 +
> .../selftests/kvm/x86_64/svm_int_ctl_test.c | 128 ++++++++++
> 8 files changed, 427 insertions(+), 48 deletions(-)
> create mode 100644 tools/testing/selftests/kvm/x86_64/svm_int_ctl_test.c
>

Queued more patches, with 9-10-11-14 left now.

Paolo

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