From: Yosry Ahmed <yosry@kernel.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
David Woodhouse <dwmw2@infradead.org>,
Paul Durrant <paul@xen.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 09/11] KVM: nSVM: Use kvm_rax_read() now that it's mode-aware
Date: Tue, 21 Apr 2026 23:19:46 +0000 [thread overview]
Message-ID: <aegGCVewI9i8dBXW@google.com> (raw)
In-Reply-To: <20260409235622.2052730-10-seanjc@google.com>
On Thu, Apr 09, 2026 at 04:56:20PM -0700, Sean Christopherson wrote:
> Now that kvm_rax_read() truncates the output value to 32 bits if the
> vCPU isn't in 64-bit mode, use it instead of the more verbose (and very
> technically slower) kvm_register_read().
>
> Note! VMLOAD, VMSAVE, and VMRUN emulation are still technically buggy,
> as they can use EAX (versus RAX) in 64-bit mode via an operand size
> prefix. Don't bother trying to handle that case, as it would require
> decoding the code stream, which would open an entirely different can of
> worms, and in practice no sane guest would shove garbage into RAX[63:32]
> and then execute VMLOAD/VMSAVE/VMRUN with just EAX.
>
> No functional change intended.
>
> Cc: Yosry Ahmed <yosry@kernel.org>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
Reviewed-by: Yosry Ahmed <yosry@kernel.org>
next prev parent reply other threads:[~2026-04-21 23:19 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-09 23:56 [PATCH 00/11] KVM: x86: Clean up kvm_<reg>_{read,write}() mess Sean Christopherson
2026-04-09 23:56 ` [PATCH 01/11] KVM: SVM: Truncate INVLPGA address in compatibility mode Sean Christopherson
2026-04-21 23:26 ` Yosry Ahmed
2026-04-09 23:56 ` [PATCH 02/11] KVM: x86/xen: Bug the VM if 32-bit KVM observes a 64-bit mode hypercall Sean Christopherson
2026-04-09 23:56 ` [PATCH 03/11] KVM: x86/xen: Don't truncate RAX when handling hypercall from protected guest Sean Christopherson
2026-04-13 10:36 ` Binbin Wu
2026-04-15 21:29 ` Sean Christopherson
2026-04-09 23:56 ` [PATCH 04/11] KVM: VMX: Read 32-bit GPR values for ENCLS instructions outside of 64-bit mode Sean Christopherson
2026-04-13 12:19 ` Huang, Kai
2026-04-15 21:37 ` Sean Christopherson
2026-04-15 23:32 ` Huang, Kai
2026-04-16 0:27 ` Sean Christopherson
2026-04-16 1:40 ` Huang, Kai
2026-04-09 23:56 ` [PATCH 05/11] KVM: x86: Trace hypercall register *after* truncating values for 32-bit Sean Christopherson
2026-04-21 23:27 ` Yosry Ahmed
2026-04-09 23:56 ` [PATCH 06/11] KVM: x86: Move kvm_<reg>_{read,write}() definitions to x86.h Sean Christopherson
2026-04-21 23:32 ` Yosry Ahmed
2026-04-22 0:40 ` Sean Christopherson
2026-04-22 20:03 ` Yosry Ahmed
2026-04-09 23:56 ` [PATCH 07/11] KVM: x86: Add mode-aware versions of kvm_<reg>_{read,write}() helpers Sean Christopherson
2026-04-14 8:26 ` Huang, Kai
2026-04-14 15:42 ` Sean Christopherson
2026-04-14 22:40 ` Huang, Kai
2026-04-14 9:02 ` Binbin Wu
2026-04-09 23:56 ` [PATCH 08/11] KVM: x86: Drop non-raw kvm_<reg>_write() helpers Sean Christopherson
2026-04-09 23:56 ` [PATCH 09/11] KVM: nSVM: Use kvm_rax_read() now that it's mode-aware Sean Christopherson
2026-04-21 23:19 ` Yosry Ahmed [this message]
2026-04-09 23:56 ` [PATCH 10/11] Revert "KVM: VMX: Read 32-bit GPR values for ENCLS instructions outside of 64-bit mode" Sean Christopherson
2026-04-16 1:42 ` Huang, Kai
2026-04-09 23:56 ` [PATCH 11/11] KVM: x86: Harden is_64_bit_hypercall() against bugs on 32-bit kernels Sean Christopherson
2026-04-16 1:43 ` Huang, Kai
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