From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 95316C3DA63 for ; Tue, 23 Jul 2024 10:07:41 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.762961.1173199 (Exim 4.92) (envelope-from ) id 1sWCQb-0007lH-Ao; Tue, 23 Jul 2024 10:07:29 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 762961.1173199; Tue, 23 Jul 2024 10:07:29 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1sWCQb-0007lA-88; Tue, 23 Jul 2024 10:07:29 +0000 Received: by outflank-mailman (input) for mailman id 762961; Tue, 23 Jul 2024 10:07:28 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1sWCQa-0007l4-9p for xen-devel@lists.xenproject.org; Tue, 23 Jul 2024 10:07:28 +0000 Received: from mail-lj1-x22d.google.com (mail-lj1-x22d.google.com [2a00:1450:4864:20::22d]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 5d4281be-48db-11ef-bbfe-fd08da9f4363; Tue, 23 Jul 2024 12:07:27 +0200 (CEST) Received: by mail-lj1-x22d.google.com with SMTP id 38308e7fff4ca-2ef2d7d8854so23032881fa.0 for ; Tue, 23 Jul 2024 03:07:27 -0700 (PDT) Received: from [10.156.60.236] (ip-037-024-206-209.um08.pools.vodafone-ip.de. [37.24.206.209]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2ccf8092da9sm8699754a91.37.2024.07.23.03.07.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Jul 2024 03:07:26 -0700 (PDT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 5d4281be-48db-11ef-bbfe-fd08da9f4363 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1721729247; x=1722334047; darn=lists.xenproject.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=p74SxLq2dEWp9ZGQVN+Lvnkp8KTTjzqhjk9NmTUGt58=; b=C8s00kctkgfFVmxqkyVpxpcsxuRD5ajz6r8mEj/ykZPC4pBG+rUOE5SxVu56fjaQrM VWYnjMc85BLGX95R/5JqDN5KdcE108HSK/s4f46/qWGa1gFbq4ze1cg+edsvlcU56GNb zgJdXpcC6JVMx2yF6AUvrahFd9s4yeKq75HSe2QDMM4cY2LiieWz6Z+au/H1CdVOjwe1 l1wDiRodzMgJ/KZWUUUlaCbqpErqcyagInEXoniVjHvRIg6NG0GVKn+n7xaWq9Nv1mq4 AqIiYAR82c9BKQebYQPTOKwVmKSlMQVmp3yHlr9xvuafSj9HuDs/aST5znRsVqjZkaGM RhxQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1721729247; x=1722334047; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=p74SxLq2dEWp9ZGQVN+Lvnkp8KTTjzqhjk9NmTUGt58=; b=pDN/TNik3Bfdju7AQNkO2jZstUlF7rRWKcMNHFEjOhmP4nwHniDGGbb85u0nkyhajr rWQKU+jtwwLob/7iyCsiI9778LiSnPdocDqtJWquyEY4rg1bxDkp8icZMFekiVb1n0up oPeV5+cdnds04joSYOUp8zxi576flT/3gcLxXoClX/g/FwelDyg0PaYog3PlIPLNiHtC O6bhlim8lOn61I/Rgc0uRY6OJC3CfJaFShea2lubaZ2bSRfJpwBxYXPiHAoTwrRIyhRt OeaIdes64z+kS5sYLLAeiAhQKqAZjl5HVWKQHVifuDAuzFoXUWcRC5/x7G/ogZheg3HS Qs+A== X-Forwarded-Encrypted: i=1; AJvYcCW+DCXgcl3NkfRQJpN92dLcTKb7fcCM/DAXzpceWSNBshX5OxS+TrkbPqq3eoPk+xgvT6N2MJkvWtYtgpQmVCXxPyGc7u0M0QitRNuFCEU= X-Gm-Message-State: AOJu0Yyb7iRjKtbfOzXCMLn5bMSF2Mpjtpro6P+kvTuILf4aBUeM6uZM wxrvFGjhBW80+cIV7buvciT3TI7lfh4dRenAfX6WkSTqS2DHZdXlUQOm/0vLDw== X-Google-Smtp-Source: AGHT+IGkYBM9ECwR7LcsuBf+IyL8oYna1/B2se7nS8kr7HptRu1RGHFB5g+m4KRfwdvK20lONG/fBw== X-Received: by 2002:a2e:240f:0:b0:2ef:a504:65b8 with SMTP id 38308e7fff4ca-2f01ea56ec0mr13847481fa.13.1721729246579; Tue, 23 Jul 2024 03:07:26 -0700 (PDT) Message-ID: <04b96cce-d2a0-4948-9db7-ee2073248472@suse.com> Date: Tue, 23 Jul 2024 12:07:20 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH for-4.19] x86/altcall: fix clang code-gen when using altcall in loop constructs To: Roger Pau Monne Cc: Andrew Cooper , Oleksii Kurochko , xen-devel@lists.xenproject.org References: <20240723093117.99487-1-roger.pau@citrix.com> Content-Language: en-US From: Jan Beulich Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: <20240723093117.99487-1-roger.pau@citrix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 23.07.2024 11:31, Roger Pau Monne wrote: > Yet another clang code generation issue when using altcalls. > > The issue this time is with using loop constructs around alternative_{,v}call > instances using parameter types smaller than the register size. > > Given the following example code: > > static void bar(bool b) > { > unsigned int i; > > for ( i = 0; i < 10; i++ ) > { > int ret_; > register union { > bool e; > unsigned long r; > } di asm("rdi") = { .e = b }; > register unsigned long si asm("rsi"); > register unsigned long dx asm("rdx"); > register unsigned long cx asm("rcx"); > register unsigned long r8 asm("r8"); > register unsigned long r9 asm("r9"); > register unsigned long r10 asm("r10"); > register unsigned long r11 asm("r11"); > > asm volatile ( "call %c[addr]" > : "+r" (di), "=r" (si), "=r" (dx), > "=r" (cx), "=r" (r8), "=r" (r9), > "=r" (r10), "=r" (r11), "=a" (ret_) > : [addr] "i" (&(func)), "g" (func) > : "memory" ); > } > } > > See: https://godbolt.org/z/qvxMGd84q > > Clang will generate machine code that only resets the low 8 bits of %rdi > between loop calls, leaving the rest of the register possibly containing > garbage from the use of %rdi inside the called function. Note also that clang > doesn't truncate the input parameters at the callee, thus breaking the psABI. > > Fix this by turning the `e` element in the anonymous union into an array that > consumes the same space as an unsigned long, as this forces clang to reset the > whole %rdi register instead of just the low 8 bits. > > Fixes: 2ce562b2a413 ('x86/altcall: use a union as register type for function parameters on clang') > Suggested-by: Jan Beulich > Signed-off-by: Roger Pau Monné Reviewed-by: Jan Beulich