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[144.49.247.120]) by smtp-relay.gmail.com with ESMTPS id 71dfb90a1353d-5633a3ed8a0sm682947e0c.6.2026.01.07.12.24.58 for (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 07 Jan 2026 12:24:58 -0800 (PST) X-Relaying-Domain: broadcom.com X-CFilter-Loop: Reflected Received: by mail-qk1-f199.google.com with SMTP id af79cd13be357-8b259f0da04so631484485a.0 for ; Wed, 07 Jan 2026 12:24:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; t=1767817497; x=1768422297; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:from:to:cc:subject:date:message-id:reply-to; bh=AojCRT0od10+Ud81n/eLNQSyI9wJA2R4G5VpVEYo8Tw=; b=WvWxSrrYZxtWgl8fGCIAP04Fs7ZXd2+qjzT/Bw+MhxNPC0ak3F9DNq5m+U01Jir33w wWB7gYAVpPdOjfOTpPrLhpZXDUVbjbFpsaDmWR6etdg+OtNvblRaVT8tIPuCn2ZjlMg8 waDSe1nzzX5lv0YdGH8ylRzc/Fbi1hm44Wt4g= X-Forwarded-Encrypted: i=1; AJvYcCXl9eigeSGJUOtqbv3ZFMd0kG6c9ELhbuwBUF9gcYznjYUz0gDrfGfRD1ZpRbzJ7cZ5L1EhGCHLc/EOhaA=@vger.kernel.org X-Received: by 2002:a05:620a:4804:b0:8b2:7536:bd2c with SMTP id af79cd13be357-8c3894188a8mr512813285a.78.1767817497596; Wed, 07 Jan 2026 12:24:57 -0800 (PST) X-Received: by 2002:a05:620a:4804:b0:8b2:7536:bd2c with SMTP id af79cd13be357-8c3894188a8mr512809585a.78.1767817497067; Wed, 07 Jan 2026 12:24:57 -0800 (PST) Received: from [10.66.193.70] ([192.19.161.250]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8c37f4b9c31sm437112185a.20.2026.01.07.12.24.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 07 Jan 2026 12:24:56 -0800 (PST) Message-ID: <75651326-1d18-4db0-8995-ff4dd6dc1da3@broadcom.com> Date: Wed, 7 Jan 2026 12:24:53 -0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RESEND 2/2] x86/paravirt: Use XOR r32,r32 to clear register in pv_vcpu_is_preempted() To: Uros Bizjak , bcm-kernel-feedback-list@broadcom.com, virtualization@lists.linux.dev, x86@kernel.org, linux-kernel@vger.kernel.org Cc: Juergen Gross , Ajay Kaher , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" References: <20260105093944.52387-1-ubizjak@gmail.com> <20260105093944.52387-2-ubizjak@gmail.com> Content-Language: en-US From: Alexey Makhalov Autocrypt: addr=alexey.makhalov@broadcom.com; keydata= xsFNBGVo9lkBEACeouRIm6Q3QTvjcnPczfBqgLffURstVJz5nqjnrNR4T+8dwNrZB8PTgOWA QdGV4bIyqtNG7UHQuZ7sVKr2tx0gYJyQ5uZgncEHB5YIuhQ/CyAHrVmO+5/0/xWCLI0g44rF ZJqsYw2JQ2+vayTWbR65rkOiKL8GOVFNZanDg80BRh6qCmCEMXd/tymxvgnvWpHtxMgukexk 4vV9nV4XhxRVYdpLk8mBxsh+AEbHE+nbWgIuJDrmrZDGI2Dha7JFoB0Mi6hbbYd9BdkcHKQ7 6c+S1xOrZL3jX7OIFhb4NNnEOhh8/+BDlyby478p6YsimNa7TgAUbrygGyfVG8usrZy8SvO+ vUbVQwqjcJaCK1xazK12dfuZm2kSMJUrJqa9ng6OMjkE2/WrtnK8ruFNSCdytzbuheT0nYUJ Uwy84cU4p2K/N2C4vYjcn+IT+l1BFr5FViKYruoRLVH6zK/WOoZjA+Fc6tdM5nC1pgSB9c7h XLQqDSzYPzk3nqeHWG1qJ0Hu7pscIrjxyNTIZ5le0TlpblJdoRcL5maDNw22yle8m4D18ERF VrqNoqwW8fObMCHbd6C3m75lzerq1HhrSvLyU4UfprEyAcjOI1C0319SXfYlXDjKXRQyaDZP wxln8uShSitSSnx0AsSAjcUa8Cc7km81+G2WSK3S2wVIAN11awARAQABzS5BbGV4ZXkgTWFr aGFsb3YgPGFsZXhleS5tYWtoYWxvdkBicm9hZGNvbS5jb20+wsGNBBMBCAA3FiEEjLzRtST/ a5u42vOKbM7yHr5SJ3cFAmVo9lwFCQ0oaIACGwMECwkIBwUVCAkKCwUWAgMBAAAKCRBszvIe vlInd0jTD/9bZtjehewLRrW3dRDAbLG/+J5g1K4X5qQPfAo42NrhZQlOTibL7ixwq7NSXynZ V4Iu9jHAW++KXjxJzkg7zjBf9OOvvgCpqZGKYgWNvHHnX4eIVh8Ikp5JtvGPMBcRv7lJA5co kb+RHo9iRrB1dvRIOsP1SlGS85SiNA0yvmgqwbigLDmDRSWtvvt9XPwU1iqF+1OopT3UE10i /z+qE2ogcw2ADveBovq2W4JeQEBvlETwDKOdh8Q3UBHOqrZUrL7YjpUxgmb89FcjdDzUU95I fCB5YxF0hUctxFH5Uujh2F4qk0m2rp7+aOGtxWCJUqkHXjgpOoxyn0FPZiZlDkst84NO5OSI 5ZFPwaFqxUrFF+cFCY2O/UE2gpoK9Lt3gYNK6o2WIAtufuiYVdK6lANMkBgZ+t2fDLIN147a 172zu8XnyJMTo+tVfUjxwqynoR/NSWpVPs0Ck3K0LGjQE0tJ6HZrH0vudXk3YaiqW+D4CtGh I17Pk0h6x8LCdjmWmuDXoc99ezOEFSyWuTHjAYxx3cmgSUyIhdHtimuf0CVLTcFoBErb/5pJ zjb11Cj0HP87FMH57bnD3qyfkBMOB6tztfdt3vkCBaWkxaiTGXNhwr4IiLUoi90yIdXDMcTj /gvnjXgN+31iYgPWgTOdUEQud0DwDwuDwkzx/0x4sF1Dfc7BTQRlaPZcARAAuGkoYKWcrCh8 5RffedM6uBZ4p5Z4+RVj05uq7hlAwhHUpLP/XGbgNzhJP375Lonmnuyg2x7oHxfiwOohuuiA MnhSeEXn2qWZJuHosrYxs9y2zyiE/GTUAcqKiYBFa/96zOaZjHpNuQ5qSHYL64WhqvtmCQYg fL+jes2Z4IXl2R7MrN9OE+G3A3pOAo8TZKUEmlUV85fSmgopIX+hCiSQmRNRtp2jK6hd2+38 YAXc+eRxYgXKaWX5zeBgNrfM7Oxeh/0iWRZPWstTvVH2xMlzywOB3e/fqg+Q3NlPGDrTyHoc L86ZELSLcMTFn+RXw8lX8oVjTcQA0M8sQHB5g0JEWtMsFjnQZkJGCfeh0Odbn/F8nZ6LQQtu +fjc/4n9vRun+PZjdhd3W9ZM9D87W9XJg9txIaYnoUXBLLpHK/OirFfr5cJTUf4svtE3EVXb x6P9vr7zqUbE0f76h1eDPmyMwFAuibIXhNoEoKQtEjLX9aKgKYny3hczRiuQpA+6U4oTNn4S /CEqphLPT53aMH0w4x0CebMPozf24ZE9YphdX8ECclLBlDL1/zx2xKrJNw8v6wdXMSfsybBW 98b5b1eVBk1uc1UMlpDl7AIHyCMTjL9Ha85eoya/Hk9l93aVHgK04hOBY2ED1/ZRpj0M5P5m tNX1JqZunpyvKooT1PrJr4UAEQEAAcLBfAQYAQgAJhYhBIy80bUk/2ubuNrzimzO8h6+Uid3 BQJlaPZeBQkNKGiAAhsMAAoJEGzO8h6+Uid3SDoQAI3XXqsehWKvyAVeGXPxmkk+Suos/nJC xZWjp4U2xbbegBnNWladZoNdlVW/WV+FSFsN5IWztxQTWBMI12A0dx+Ooi9PSIANnlN+gQsA 9WeQ5iDNveEHZyK1GmuqZ3M3YZ1r3T2KyzTnPPZQ1B8gMQ442bOBWe077MqtLaC0J1jHyWHU j6BbUCAyR2/OCV/n1bH4wYIm2lgrOd2WuzoAGvju+j2g7hMRxw/xeHeu8S0czHuEZ0dC6fR1 ZKUOw03+mM/xRzL1be6RVS9AF7R5oDd11RrTOb7k14z0inFqSRrRwzOPKcuMxrApcquar336 3FQuLcJLjBo/SAOh2JatOkkwkw5PZseqdwcAk5+wcCbdYy8J8ttR04iV1FzrdQp8HbVxGNo7 AlDn1qtoHzvJHSQG51tbXWfLIi1ek3tpwJWj08+Zo+M47X6B65g7wdrwCiiFfclhXhI1eJNy fqqZgi3rxgu4sc5lmR846emZ/Tx85/nizqWCv7xUBxQwmhRPZRW+37vS2OLpyrTtBj3/tEM9 m9GMmTZqaJFeK7WCpprJV4jNHpWZuNAsQrdK1MrceIxb0/6wYe0xK79lScxms+zs9pGTrO4U 5RoS4gXK65ECcBH8/mumV6oBmLrNxKUrzTczdo9PnkmRyZcAa6AndbjmQDznwxvTZu2LjMPC EuY0 In-Reply-To: <20260105093944.52387-2-ubizjak@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e On 1/5/26 1:39 AM, 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 > Reviewed-by: Juergen Gross > Cc: Ajay Kaher > Cc: Alexey Makhalov > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: Borislav Petkov > Cc: Dave Hansen > Cc: "H. Peter Anvin" > --- > arch/x86/include/asm/paravirt.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h > index 4f6ec60b4cb3..59aec695ae5f 100644 > --- a/arch/x86/include/asm/paravirt.h > +++ b/arch/x86/include/asm/paravirt.h > @@ -577,7 +577,7 @@ static __always_inline void pv_kick(int cpu) > static __always_inline bool pv_vcpu_is_preempted(long cpu) > { > return PVOP_ALT_CALLEE1(bool, lock.vcpu_is_preempted, cpu, > - "xor %%" _ASM_AX ", %%" _ASM_AX, > + "xor %%eax, %%eax", > ALT_NOT(X86_FEATURE_VCPUPREEMPT)); > } > Acked-by: Alexey Makhalov