From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 93054944F for ; Sun, 18 Aug 2024 06:17:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723961851; cv=none; b=ppiX2Obrz6LnIXFeR4EXmi25lGfuREF6u9MUt+FMsKN7mRQhkhJkRxwL0KN51q9YCbwB0aGmjzsBH9pVMgq7ifuNbpHhnOj4WLDMpEma3TNKrfYV8zVdw+9Jgv6qHQuE33oJ+pgra/wFfa/r3r9Aq3c6NTMePf8jPBxOSXdc5ns= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723961851; c=relaxed/simple; bh=oOGDZD/wdXb4QFfc/oKPu3+MuFOtbGpBFYaC/iwKBLg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=MV8kVqC0VsTtl9avbIz+ywkfOLsrP7yuGMT6sWQym9UK0oETCRgICRQ2Q5DRr/SWDGDk2OFjPMNYrWnSoKnLCjMdxr8T51U4rV8+q/2ll+Xp1uRu95LLsZb1EaAZ6ZOttkK4iFwBQBWi6Mog1YPG7qen/+i8xFGlmP/dPwvce70= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=YX1OY92x; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="YX1OY92x" Received: from [IPV6:2601:646:8002:4641:eb14:ad94:2806:1c1a] ([IPv6:2601:646:8002:4641:eb14:ad94:2806:1c1a]) (authenticated bits=0) by mail.zytor.com (8.17.2/8.17.1) with ESMTPSA id 47I6GfGW299775 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Sat, 17 Aug 2024 23:16:41 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 47I6GfGW299775 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2024071601; t=1723961804; bh=wIslcl7OOpcz8rPD/i3Svi+vXIL54ttTesBrOTxqguo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=YX1OY92xGWbBUTAcIWBGZWjUYTgCvXF1MnWsHDDioN72xjJ8SsMfDXryUVP1MaAqq nwOiqdoQ9LHMFKFdRVxHN4lBhZMY9wjHjHCwk6rXssdAwMv2PziUw63LH1jp9J8Ga0 IzY0G5hhbUEvyV1MEo9wMWXWgEFx4qi6NZZgs5Yv8pAjam753KN+AYWKj+zAdxVMLQ 1JWuanS9H38u57v3VO2XU7imkMMSeD6Zd/+EtPfRnc6fAidyav82XlXHknfMBcDdoc Cez2qqtV6HTfs1FhfGkfeQh4ihw+vY3OtzHQ2CLd9IFQgrchfReaf0y0lPtDMCVh9h mOtw9Ca4F/8tQ== Message-ID: Date: Sat, 17 Aug 2024 23:16:36 -0700 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 v1 2/3] x86/msr: Switch between WRMSRNS and WRMSR with the alternatives mechanism To: Borislav Petkov Cc: Xin Li , Andrew Cooper , linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, peterz@infradead.org, seanjc@google.com References: <20240807054722.682375-1-xin@zytor.com> <20240807054722.682375-3-xin@zytor.com> <7c09d124-08f1-40b4-813c-f0f74e19497a@zytor.com> <20240818054911.GAZsGLV1MAEMLk9RiP@fat_crate.local> Content-Language: en-US From: "H. Peter Anvin" In-Reply-To: <20240818054911.GAZsGLV1MAEMLk9RiP@fat_crate.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/17/24 22:49, Borislav Petkov wrote: > On Sat, Aug 17, 2024 at 12:22:22PM -0700, H. Peter Anvin wrote: >> The padding avoids unnecessary NOPs. > > And a NOP vs some other prefix to have one less insn matters practically > how exactly here? Pretty much nothing, but it is zero cost and possibly some insanely small gain. -hpa