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 A88092FE579; Tue, 10 Feb 2026 22:53:26 +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=1770764008; cv=none; b=KsbN7bX3kF1pDK5Joi7h8jw8xBRQumQuTkNcoPGpx1YvQo6jF8+3l9g/LoMAzYqWR25HENA70CsWnEWWvnt7jBwocxbDrRFNJ/d/wn58u+D4bVHiROTU9HbwR5+5tiQRggKhQEZaCxOYijzePZS5zLGN+3rfloanraq8TqH3tEM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770764008; c=relaxed/simple; bh=AHbiyaawWzFPubJS9zsKj1xRN7M0Og7yWqxxCClQNfw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=DS1GSEYM344QRIKv24acMf0HsZXiOg8th/nc+JcQyinfZxaOEN6jiyDo2AhsDBPiENxijeyG/4BQPf11+t31bWro3nqGlBL4aa2w4qvIuzANwrbbZhp21tQyaJiWdFNIpOv6tDZgCvXbKXg1M08CrmDiZ5CztVTQefUi77Mpc1A= 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=hAHwXVxF; 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="hAHwXVxF" 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 61AMqfJn3574887 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Tue, 10 Feb 2026 14:52:49 -0800 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 61AMqfJn3574887 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2026012301; t=1770763970; bh=/JVwO5GqZyRu4wslqfDAhOYGhuMqZ/no6z2KyqqMrrY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=hAHwXVxFx5gqlfTFo0/gyNlXYQGyG16+cRGFk2IqI/h4lJycl1YZ97q4FTjUU+xYT mM31ROJYLaK8oqNutqeK/8rYNWOMrwXdeWEN3YBPWsbpFHa7sE8F01H+LtFzOQlpE/ jI5VVFqpsAoAWAaMIJP7/DT38rlWrlTaJB1Bm5l5NhyVQg/7h+nBg6BzWvLr703GCm vGDbTM9zlHstq+R/V50AdmgbNmSJWxhrrCvyFkAfpR3WtV4IRtlS3aZkMhd+v5uJYv 7QrhKD3s2RLTLzW5uZVULcw/UDch7w2sqHkafEjjMMPWrD4iJbGFj/e7eKxpQnFX4M 5qNmAx2H0G24w== Message-ID: <90543b26-1e09-4a84-802e-aad737265b7a@zytor.com> Date: Tue, 10 Feb 2026 14:52:36 -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 v2 3/3] x86/hyperv: Remove ASM_CALL_CONSTRAINT with VMMCALL insn To: Uros Bizjak Cc: linux-hyperv@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Michael Kelley , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen References: <20251121141437.205481-1-ubizjak@gmail.com> <20251121141437.205481-3-ubizjak@gmail.com> <8F5147DF-E0E2-4942-99D9-4242F3013635@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 2025-11-22 01:33, Uros Bizjak wrote: >> >> I think it would be good to have a comment at the point where ASM_CALL_CONSTRAINT is defined explaining its proper use. >> >> Specifically, instructions like syscall, vmcall, vmfunc, vmmcall, int xx and VM-specific escape instructions are not "calls" because they either don't modify the stack or create an exception frame (kernel) or signal frame (user space) which is completely special. > > The existing comment already mentions CALL instruction only: > > /* > * This output constraint should be used for any inline asm which has a "call" > * instruction. Otherwise the asm may be inserted before the frame pointer > * gets set up by the containing function. If you forget to do this, objtool > * may print a "call without frame pointer save/setup" warning. > */ > Yes. Some people seem to have misunderstood it to mean any instruction with "CALL" in the name. -hpa