linux-kernel - Re: [PATCH 0/9] KVM: SVM: Fix and clean up "can emulate" mess

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Message-ID: <d02e3982-b34c-c529-11b5-4c788af480d2@oracle.com>
Date:   Thu, 20 Jan 2022 16:58:07 +0000
From:   Liam Merwick <liam.merwick@...cle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Brijesh Singh <brijesh.singh@....com>,
        Liam Merwick <liam.merwick@...cle.com>
Subject: Re: [PATCH 0/9] KVM: SVM: Fix and clean up "can emulate" mess

On 20/01/2022 01:07, Sean Christopherson wrote:
> Revert an amusing/embarassing goof reported by Liam Merwick, where KVM
> attempts to determine if RIP is backed by a valid memslot without first
> translating RIP to its associated GPA/GFN.  Fix the underlying bug that
> was "fixed" by the misguided memslots check by (a) never rejecting
> emulation for !SEV guests and (b) using the #NPF error code to determine
> if the fault happened on the code fetch or on guest page tables, which is
> effectively what the memslots check attempted to do.
> 
> Further clean up, harden, and document SVM's "can emulate" helper, and
> fix a #GP interception SEV bug found in the process of doing so.


FYI: I've applied all 9 commits to a 5.15 based branch (applied cleanly)
and the 3 stable candidates to a 5.4 based branch (applied with minor
contextual conflicts) and have been running my SEV test case (sysbench)
and kvm-unit-tests without issues for a number of hours now.

Regards,
Liam


> 
> Sean Christopherson (9):
>    KVM: SVM: Never reject emulation due to SMAP errata for !SEV guests
>    Revert "KVM: SVM: avoid infinite loop on NPF from bad address"
>    KVM: SVM: Don't intercept #GP for SEV guests
>    KVM: SVM: Explicitly require DECODEASSISTS to enable SEV support
>    KVM: x86: Pass emulation type to can_emulate_instruction()
>    KVM: SVM: WARN if KVM attempts emulation on #UD or #GP for SEV guests
>    KVM: SVM: Inject #UD on attempted emulation for SEV guest w/o insn
>      buffer
>    KVM: SVM: Don't apply SEV+SMAP workaround on code fetch or PT access
>    KVM: SVM: Don't kill SEV guest if SMAP erratum triggers in usermode
> 
>   arch/x86/include/asm/kvm_host.h |   3 +-
>   arch/x86/kvm/svm/sev.c          |   9 +-
>   arch/x86/kvm/svm/svm.c          | 162 ++++++++++++++++++++++----------
>   arch/x86/kvm/vmx/vmx.c          |   7 +-
>   arch/x86/kvm/x86.c              |  11 ++-
>   virt/kvm/kvm_main.c             |   1 -
>   6 files changed, 135 insertions(+), 58 deletions(-)
> 
> 
> base-commit: edb9e50dbe18394d0fc9d0494f5b6046fc912d33