linux-kernel - Re: [PATCH 2/2] x86/paravirt: Use XOR r32,r32 to clear register in pv_vcpu_is

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Message-ID: <c9228c34-287e-43be-8d7b-6299b165dd6a@suse.com>
Date: Tue, 25 Nov 2025 14:44:03 +0100
From: Jürgen Groß <jgross@...e.com>
To: Uros Bizjak <ubizjak@...il.com>, bcm-kernel-feedback-list@...adcom.com,
 virtualization@...ts.linux.dev, x86@...nel.org, linux-kernel@...r.kernel.org
Cc: Ajay Kaher <ajay.kaher@...adcom.com>,
 Alexey Makhalov <alexey.makhalov@...adcom.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 2/2] x86/paravirt: Use XOR r32,r32 to clear register in
 pv_vcpu_is_preempted()

On 20.11.25 20:15, Uros Bizjak wrote:
> x86_64 zero extends 32bit operations, so for 64bit operands,
> XOR r32,r32 is functionally equal to XOR r64,r64, but avoids
> a REX prefix byte when legacy registers are used.
> 
> Signed-off-by: Uros Bizjak <ubizjak@...il.com>

Reviewed-by: Juergen Gross <jgross@...e.com>

Juergen

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