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 289C0392C50 for ; Thu, 12 Mar 2026 19:11:35 +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=1773342697; cv=none; b=eIclwCUpxFoHP8LQL4Oq9AOsBQOnPqWDas79J9Y4yC8UD0z7XOrHfaNy6F98MhFM1xkEHm9x7vvk7CTA11XB0EDCpbqOpLzzL2bafiAdCZ3o5hkMuzBjHp47VC77wfm8HBuK5AWHf7cdkd6nJEObmgxVY38jKEnbGF1CIg8NZWg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773342697; c=relaxed/simple; bh=bc/ZHH6QhUkIVsoMI5Nnu7IHtmTvk3U8VadE4KPoggE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Vw5CIA1SKuMF8qjGHoWMZaOAH7TvxEWhNNM4+jWt67xpItTarRL8vpPwDKp0mVdtzsftUPjq6Zm5kPt+rQYDiewW2PDpFOJ1gyroo6rMVCwWzkxk5Pc+8eIyTW7aebBCV60jIcLNoUA9I/3JlVtaGgBeWNK1xdBFgf89rbGtlxw= 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=LLE6yi/t; 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="LLE6yi/t" Received: from [172.27.2.41] (c-76-133-66-138.hsd1.ca.comcast.net [76.133.66.138]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 62CIt6Dx2921414 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Thu, 12 Mar 2026 11:55:07 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 62CIt6Dx2921414 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2026022301; t=1773341707; bh=w4xdaI5cI4YHCL1OYl0KpOUi/dEyd33MMMy/ebJIjaM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=LLE6yi/tUhnfn+61lUCMyQdG9euNlUgABIvqtJLlKJp2PUzI1UrWcTzXQ+6F7rf7J FJ/fi5bnZ4fDTr0Xpi72KYKSpvxu4mbJWr5eqlU5XQ8VhF5nT7niMok5DJ9ZtgOZTu qol25pRrY9+Hd0MclZXvZozGOYO+CsThp5VfaK9QUtrCnqh2ACC30eFU7PmoEa1Xdj J1euUUExEjB8hDM3Z1HTjz57JLvwWbcbjzkY1z6u5ewPKy13oXwh0oM2fdctbXYjkI RDdCVgTjKI/vlBd9h/w8vyoQnEikvmk5+kUb2tUggjzNcRUmTL3cMlMok86fAbIjx4 +7QimWLUUHuDg== Message-ID: <6b1d157d-c549-4f5a-a0d4-602bf2e86b97@zytor.com> Date: Thu, 12 Mar 2026 11:55:01 -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: [tip: x86/cleanups] x86/segment: Use MOVL when reading segment registers To: Uros Bizjak Cc: linux-kernel@vger.kernel.org, "Borislav Petkov (AMD)" , x86@kernel.org, Dave Hansen , Ingo Molnar , Thomas Gleixner , Peter Zijlstra , David Laight References: <20260105090422.6243-1-ubizjak@gmail.com> <176891088183.510.8607818928752445249.tip-bot2@tip-bot2> <3A54B6DC-2462-41DA-8C34-D38CCD2A9A2B@zytor.com> Content-Language: en-US, sv-SE From: "H. Peter Anvin" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2026-03-12 02:30, Uros Bizjak wrote: > > We would like to always use MOVL to avoid 0x66 operand size override > prefix when reading to a register, but MOVL does not support memory > operands. MOVW is required in this case. > Just use "mov" without any suffix. GAS LISTING movseg.s page 1 1 .text 2 3 0000 8CD8 mov %ds,%eax 4 0002 668CD8 mov %ds,%ax 5 0005 8C1B mov %ds,(%rbx) -hpa