From: Sean Christopherson <seanjc@google.com>
To: Hao Zhang <hao_zhang_kdev@163.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: x86: Emulate SYSENTER in 64-bit mode for Intel-compatible vCPUs
Date: Wed, 4 Nov 2026 11:58:56 -0800 [thread overview]
Message-ID: <auuOgNrHhlXSKDRV@google.com> (raw)
In-Reply-To: <atge--CosCmrOcx6@192.168.1.215>
On Wed, Oct 21, 2026, Hao Zhang wrote:
> From: Hao Zhang <zhanghao1@kylinos.cn>
>
> Intel allows SYSENTER in both IA-32e submodes, whereas AMD raises #UD
> in either submode. On AMD hosts, KVM intercepts #UD and emulates
> SYSENTER to support Intel-compatible vCPUs.
>
> However, em_sysenter() unconditionally rejects execution from 64-bit
> mode. As a result, a valid SYSENTER in an Intel-compatible guest can
> fail emulation instead of entering the guest's kernel. For a
> non-nested guest at CPL0, this results in a
> KVM_INTERNAL_ERROR_EMULATION exit to userspace even when
> KVM_CAP_EXIT_ON_EMULATION_FAILURE is not enabled.
>
> Remove the unconditional rejection.
Why? I'm not inclined to expand the emulator's capabilities for something like
this without a *really* good reason to do so.
prev parent reply other threads:[~2026-11-04 19:58 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-21 2:10 Hao Zhang
2026-11-04 19:58 ` Sean Christopherson [this message]
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