linux-kernel - Re: [PATCH 0/5] KVM: x86: Fix breakage in KVM_SET

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Date:   Wed,  4 Oct 2023 18:29:23 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Shuah Khan <shuah@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-kselftest@...r.kernel.org, llvm@...ts.linux.dev,
        Tyler Stachecki <stachecki.tyler@...il.com>,
        Leonardo Bras <leobras@...hat.com>
Subject: Re: [PATCH 0/5] KVM: x86: Fix breakage in KVM_SET_XSAVE's ABI

On Wed, 27 Sep 2023 17:19:51 -0700, Sean Christopherson wrote:
> Rework how KVM limits guest-unsupported xfeatures to effectively hide
> only when saving state for userspace (KVM_GET_XSAVE), i.e. to let userspace
> load all host-supported xfeatures (via KVM_SET_XSAVE) irrespective of
> what features have been exposed to the guest.
> 
> The effect on KVM_SET_XSAVE was knowingly done by commit ad856280ddea
> ("x86/kvm/fpu: Limit guest user_xfeatures to supported bits of XCR0"):
> 
> [...]

Applied to kvm-x86 fpu, even though there is still ongoing discussion.  I want
to get this exposure in -next sooner than later.  I'll keep this in its own
branch so it'll be easier to rewrite/discard if necessary.

[1/5] x86/fpu: Allow caller to constrain xfeatures when copying to uabi buffer
      https://github.com/kvm-x86/linux/commit/2d287ec65e79
[2/5] KVM: x86: Constrain guest-supported xfeatures only at KVM_GET_XSAVE{2}
      https://github.com/kvm-x86/linux/commit/27526efb5cff
[3/5] KVM: selftests: Touch relevant XSAVE state in guest for state test
      https://github.com/kvm-x86/linux/commit/ff0654c71fb6
[4/5] KVM: selftests: Load XSAVE state into untouched vCPU during state test
      https://github.com/kvm-x86/linux/commit/d7b8762ec4a3
[5/5] KVM: selftests: Force load all supported XSAVE state in state test
      https://github.com/kvm-x86/linux/commit/afb2c7e27a7f

--
https://github.com/kvm-x86/linux/tree/next