linux-kernel - Re: [PATCH v3 0/4] Handle #GP for SVM execution instructions

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Message-ID: <3349e153-83ae-3c55-ee88-2036b2ce38d8@redhat.com>
Date:   Tue, 26 Jan 2021 12:39:28 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wei Huang <wei.huang2@....com>, kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, vkuznets@...hat.com,
        mlevitsk@...hat.com, seanjc@...gle.com, joro@...tes.org,
        bp@...en8.de, tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
        jmattson@...gle.com, wanpengli@...cent.com, bsd@...hat.com,
        dgilbert@...hat.com, luto@...capital.net
Subject: Re: [PATCH v3 0/4] Handle #GP for SVM execution instructions

On 26/01/21 09:18, Wei Huang wrote:
> While running SVM related instructions (VMRUN/VMSAVE/VMLOAD), some AMD
> CPUs check EAX against reserved memory regions (e.g. SMM memory on host)
> before checking VMCB's instruction intercept. If EAX falls into such
> memory areas, #GP is triggered before #VMEXIT. This causes unexpected #GP
> under nested virtualization. To solve this problem, this patchset makes
> KVM trap #GP and emulate these SVM instuctions accordingly.
> 
> Also newer AMD CPUs will change this behavior by triggering #VMEXIT
> before #GP. This change is indicated by CPUID_0x8000000A_EDX[28]. Under
> this circumstance, #GP interception is not required. This patchset supports
> the new feature.
> 
> This patchset has been verified with vmrun_errata_test and vmware_backdoor
> tests of kvm_unit_test on the following configs. Also it was verified that
> vmware_backdoor can be turned on under nested on nested.
>    * Current CPU: nested, nested on nested
>    * New CPU with X86_FEATURE_SVME_ADDR_CHK: nested, nested on nested
> 
> v2->v3:
>    * Change the decode function name to x86_decode_emulated_instruction()
>    * Add a new variable, svm_gp_erratum_intercept, to control interception
>    * Turn on VM's X86_FEATURE_SVME_ADDR_CHK feature in svm_set_cpu_caps()
>    * Fix instruction emulation for vmware_backdoor under nested-on-nested
>    * Minor comment fixes
> 
> v1->v2:
>    * Factor out instruction decode for sharing
>    * Re-org gp_interception() handling for both #GP and vmware_backdoor
>    * Use kvm_cpu_cap for X86_FEATURE_SVME_ADDR_CHK feature support
>    * Add nested on nested support
> 
> Thanks,
> -Wei
> 
> Wei Huang (4):
>    KVM: x86: Factor out x86 instruction emulation with decoding
>    KVM: SVM: Add emulation support for #GP triggered by SVM instructions
>    KVM: SVM: Add support for SVM instruction address check change
>    KVM: SVM: Support #GP handling for the case of nested on nested
> 
>   arch/x86/include/asm/cpufeatures.h |   1 +
>   arch/x86/kvm/svm/svm.c             | 128 +++++++++++++++++++++++++----
>   arch/x86/kvm/x86.c                 |  62 ++++++++------
>   arch/x86/kvm/x86.h                 |   2 +
>   4 files changed, 152 insertions(+), 41 deletions(-)
> 

Queued, thanks.

Paolo