From: Dave Hansen <dave.hansen@intel.com>
To: "Chang S. Bae" <chang.seok.bae@intel.com>,
pbonzini@redhat.com, seanjc@google.com
Cc: kvm@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org, chao.gao@intel.com
Subject: Re: [PATCH v4 06/21] x86/fpu: Ignore APX when copying from/to guest FPU
Date: Wed, 13 May 2026 12:10:58 -0700 [thread overview]
Message-ID: <6adbdfb5-c4fa-455b-b427-2f8350bc9c2e@intel.com> (raw)
In-Reply-To: <20260512011502.53072-7-chang.seok.bae@intel.com>
On 5/11/26 18:14, Chang S. Bae wrote:
> From: Paolo Bonzini <pbonzini@redhat.com>
>
> KVM will store APX extended GPRs directly in the regs[] field of struct
> kvm_vcpu. This is done to make accessors more uniform between GPRs and
> EGPRs, and partly because x86 maintainers expressed the desire to compile
> Linux with APX enabled sooner or later; accessing guest EGPRs from KVM's
> C code would get in the way.
>
> Therefore, let KVM handle the APX feature on its own when executing
> ioctls to get and set the virtual machine's XSAVE state.
I'm sure this works.
But it does look a bit hacky to me. I just despise adding new special
cases to the XSAVE code when we don't _have_ to.
Couldn't we, for instance, just let the APX registers use the "fpu"
ABIs? PKRU is weird too, but it still gets to use those ABIs.
Having space for the eGPRs in one more place seems like additional
confusion.
next prev parent reply other threads:[~2026-05-13 19:11 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 1:14 [PATCH v4 00/21] KVM: x86: Enable APX for guests Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 01/21] KVM: VMX: Macrofy GPR swapping in __vmx_vcpu_run() Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 02/21] KVM: SVM: Macrofy GPR swapping in __svm_vcpu_run() Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 03/21] KVM: SEV: Macrofy GPR swapping in __svm_sev_es_vcpu_run() Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 04/21] KVM: x86: Extend VCPU registers for EGPRs Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 05/21] KVM: VMX: Save guest EGPRs in VCPU cache Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 06/21] x86/fpu: Ignore APX when copying from/to guest FPU Chang S. Bae
2026-05-13 17:42 ` Paolo Bonzini
2026-05-13 19:10 ` Dave Hansen [this message]
2026-05-12 1:14 ` [PATCH v4 07/21] KVM: x86: Support APX state for XSAVE ABI Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 08/21] KVM: VMX: Refactor VMX instruction information access Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 09/21] KVM: VMX: Refactor instruction information decoding Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 10/21] KVM: VMX: Refactor register index retrieval from exit qualification Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 11/21] KVM: VMX: Support instruction information extension Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 12/21] KVM: nVMX: Propagate the extended instruction info field Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 13/21] KVM: x86: Support EGPR accessing and tracking for emulator Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 14/21] KVM: x86: Handle EGPR index and REX2-incompatible opcodes Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 15/21] KVM: x86: Support REX2-prefixed opcode decode Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 16/21] KVM: x86: Reject EVEX-prefixed instructions Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 17/21] KVM: x86: Guard valid XCR0.APX settings Chang S. Bae
2026-05-12 1:14 ` [PATCH v4 18/21] KVM: x86: Expose APX foundation feature to guests Chang S. Bae
2026-05-12 1:15 ` [PATCH v4 19/21] KVM: x86: Expose APX sub-features " Chang S. Bae
2026-05-12 1:15 ` [PATCH v4 20/21] KVM: x86: selftests: Add APX state and ABI test Chang S. Bae
2026-05-12 1:15 ` [PATCH v4 21/21] KVM: x86: selftests: Add APX state handling and XCR0 sanity checks Chang S. Bae
2026-05-13 17:52 ` [PATCH v4 00/21] KVM: x86: Enable APX for guests Paolo Bonzini
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