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 2912DC5DF67 for ; Tue, 18 Aug 2026 07:56:21 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.1393594.1632415 (Exim 4.92) (envelope-from ) id 1wwEg7-000356-W1; Tue, 18 Aug 2026 07:56:11 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 1393594.1632415; Tue, 18 Aug 2026 07:56:11 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1wwEg7-00034z-Rf; Tue, 18 Aug 2026 07:56:11 +0000 Received: by outflank-mailman (input) for mailman id 1393594; Tue, 18 Aug 2026 07:56:11 +0000 Received: from mx.expurgate.net ([195.190.135.20]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1wwEg6-00034t-UL for xen-devel@lists.xenproject.org; Tue, 18 Aug 2026 07:56:11 +0000 Received: from mx.expurgate.net (helo=localhost) by mx.expurgate.net with esmtp id 1wwEg6-001oVA-Aq for xen-devel@lists.xenproject.org; Tue, 18 Aug 2026 09:56:10 +0200 Received: from [10.42.69.7] (helo=localhost) by localhost with ESMTP (eXpurgate MTA 0.9.1) (envelope-from ) id 6a841002-bab6-0a2a0a5309dd-0a2a45078cbc-34 for ; Tue, 18 Aug 2026 09:56:05 +0200 Received: from [209.85.221.41] (helo=mail-wr1-f41.google.com) by tlsNG-ef75cf.mxtls.expurgate.net with ESMTPS (eXpurgate 4.57.1) (envelope-from ) id 6a841014-b4ea-0a2a45070019-d155dd29e83f-3 for ; Tue, 18 Aug 2026 09:56:05 +0200 Received: by mail-wr1-f41.google.com with SMTP id ffacd0b85a97d-47f6609c657so2067045f8f.2 for ; Tue, 18 Aug 2026 00:56:05 -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 ffacd0b85a97d-482a5b77fa3sm9639633f8f.26.2026.08.18.00.56.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Aug 2026 00:56:04 -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" Authentication-Results: eu.smtp.expurgate.cloud; dkim=pass header.s=google header.d=suse.com header.i="@suse.com" header.h="Content-Transfer-Encoding:Content-Type:In-Reply-To:Autocrypt:From:Content-Language:References:Cc:To:Subject:User-Agent:MIME-Version:Date:Message-ID" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1787039764; x=1787644564; darn=lists.xenproject.org; h=content-transfer-encoding:content-type: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 :content-type; bh=zXEcZZ29k+TvYgFCA8ciZUZEguthu2ZUBj81fxlkawM=; b=Y3VBxJXf3gN0wAz7XUeiPBaWvkBu1K97eWZm4u/3CBY5/Wt+1npLVQ3bX8q3kt6lj1 iLo46s56w2NrPFMmE5d/sMci+k3TgwADwW7A/ERI/0TXCngT1I9nFX2pnW6mTzI0kuBm /ToRdP9/bsfFwx3dFNMZUt1Aq+nRfYZLstt1KEII0PDLAujXajOYbRqnuvGiMD6teuBo iIAPRGvn9OOd9jKp4iRU5eX5Yw6tMkg6xxYA4byIilxnnHfpRaWuS52Yx0ubknvGYC00 ++oe1gaCzNjWbPgKCZHdATH5BfjSq69ea+wMcHyO8hbo9v941timHmd7yTdEzAd04JCx ZAnQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787039764; x=1787644564; h=content-transfer-encoding:content-type:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=zXEcZZ29k+TvYgFCA8ciZUZEguthu2ZUBj81fxlkawM=; b=SmSZbhCd+mq0JUMGfL8xJm2/NvX7/r3qmgE1VRqUo6xIe3oxt8T6IGqjuFTE30jOMg UWYnPZW5hlHHwl7c9p75/KKN3DC0xxrqBWp3puXwcetlJj8NxEOSEE5ZhEkiodJq+lXz KZNfGmwdTNqddJ6Q4x5KU7Km6IaEyvyJUWkNpJfry1hdQs5FoGxD7Fbq+yEMuVw30iBw HzaQtV+fualRJ0b8qsFXiAk9m6q0Pr5Xa94mtBQhnLnLvGOdUE6orWVil9MPjBIIQyN+ DnDkfJrgk1ho1XGdVYJ68TPG/arFo3rdpRwnjI6frAdAMoxG/Mothvu6RdgjtZn93qbQ 5Iow== X-Forwarded-Encrypted: i=1; AHgh+RrOKBu6K1ax5ZeuWS1r5oqFpU6Z02woYbCIkBCU+nO5YPQNYkNYEhbR60qRQtR/3Uwu6PTknkMCYMA=@lists.xenproject.org X-Gm-Message-State: AOJu0YydBfL1MIAyfzvy8aWYUDhZJIHJG7+2BU7sIoZeACnDzQGESoLT nWbG26jmC13p2LyAZk7XN6DEm9cmaQD7CXAh5AITw32Qaigw0xSujvtlzuQ1SEH69A== X-Gm-Gg: AR+sD10wrEPw1O3AHn1coNZwazEcnWGr1kY1dQcAsx5bMdKY5unBJrb/QG5DCa2v79D QhdP//3EipresN77sGizoTsoP0XQtyx7xV3QNoecAkEEGfY4xbTz5t87kJyhfb9ZYkjPyPEHmAP YooodAOe8p9QQJ1cZcU2lBszN5r3Kit1WXeV0Vyq8V1uPX7Q7Uu7BdOiab58+0Zinlj28/v48lq 7OA6wD270oIYXItn2fpYivcC0LrOJCmbs2H7Op56dvOqiJNY933HSniWOYGAtJ2cxGUsYFNXi6g 5D11yvQ6uWA2SawbsFqjIChH+w/rkfDHpvGiZWlCURwQtxJwU0/o6qROSf8BS0v6fNcrwS509YR NDZFXCWb9wvDVx7bpzTtcQXVPDU/xCNaRhB/Uac5nHyRxmY96AUwQWdB9/52SVvXuVzWQQkOKPY VbyyEZBTic1xOIO/oPQR8XCs7nOVbedCkBgtzWgLH542OGNpHjDDcxADY1MXr8h15srz/k9/AO4 LE69CJiV2olYiJ9veGzxeT9HIgQQuQojktiGSQMPtIbqllRsPDX X-Received: by 2002:a05:6000:410a:b0:47f:8b2c:3d98 with SMTP id ffacd0b85a97d-48160723cd4mr47724056f8f.4.1787039764518; Tue, 18 Aug 2026 00:56:04 -0700 (PDT) Message-ID: Date: Tue, 18 Aug 2026 09:56:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 12/17] xen/riscv: extend exception tables with type and data fields To: Oleksii Kurochko Cc: Romain Caritey , Baptiste Le Duc , Alistair Francis , Connor Davis , Andrew Cooper , Anthony PERARD , Michal Orzel , xen-devel@lists.xenproject.org, Julien Grall , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Stefano Stabellini References: <1eb9050ff6632f91682151471440990bd718ed90.1784560663.git.oleksii.kurochko@gmail.com> <3c9ef195-a8d4-489c-8daf-5635d3b53063@gmail.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: <3c9ef195-a8d4-489c-8daf-5635d3b53063@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-purgate-ID: tlsNG-ef75cf/1787039765-352CCAE4-189113E2/0/0 X-purgate-type: clean X-purgate-size: 4888 On 17.08.2026 13:33, Oleksii Kurochko wrote: > On 8/12/26 4:37 PM, Jan Beulich wrote: >> On 20.07.2026 18:02, Oleksii Kurochko wrote: >>> @@ -60,6 +68,40 @@ static void ex_handler_fixup(const struct exception_table_entry *ex, >>> regs->sepc = ex_fixup(ex); >>> } >>> >>> +static inline unsigned long regs_get_gpr(struct cpu_user_regs *regs, >>> + unsigned int offset) >>> +{ >>> + /* >>> + * The GPR number -> offset arithmetic below relies on x0..x31 being >>> + * laid out at the start of struct cpu_user_regs in architectural >>> + * order. >>> + */ >>> + BUILD_BUG_ON(offsetof(struct cpu_user_regs, ra) != >>> + sizeof(unsigned long)); >>> + BUILD_BUG_ON(offsetof(struct cpu_user_regs, t6) != >>> + 31 * sizeof(unsigned long)); >>> + >>> + if ( unlikely(!offset || (offset > MAX_REG_OFFSET)) ) >>> + return 0; >> >> And an offset not divisible by sizeof(unsigned long) is okay? > > No, it isn't okay. I will apply your comment ... > >> >> Returning 0 as error indicator also feels fragile. > > With what I suggested below returning could be just dropped. > >> >>> + return *(unsigned long *)((unsigned long)regs + offset); >>> +} >>> + >>> +static void ex_handler_trap_info(const struct exception_table_entry *ex, >>> + struct cpu_user_regs *regs) >>> +{ >>> + struct trap_info *trap_info = >>> + (struct trap_info *)regs_get_gpr(regs, ex->data * sizeof(unsigned long)); >> >> Related to the earlier comment: Simply pass just ex->data here, leaving the >> multiplication to regs_get_gpr()? > > ... It would be better to move the multiplication inside regs_get_gpr(). > > Your comment made me think about whether the multiplication is needed at > all (regardless of where it is done). In other words, ex->data contains > the register number, so we could just write: > > static unsigned long regs_get_gpr(const struct cpu_user_regs *regs, > unsigned int num) > { > /* > * The GPR number -> offset arithmetic below relies on x0..x31 being > * laid out at the start of struct cpu_user_regs in architectural > order. > */ > BUILD_BUG_ON(offsetof(struct cpu_user_regs, ra) != sizeof(unsigned > long)); > BUILD_BUG_ON(offsetof(struct cpu_user_regs, t6) != 31 * > sizeof(unsigned long)); > > ASSERT(num && (num < 32)); > > return ((const unsigned long *)regs)[num]; > } > > Probably, we want to consider this function out of context (for now > context is that we use it to recieve a pointer to trap_info which can't > be obviously stored in x0 as it should be always hardwired zero). In > that case, there is no need to check that num is 0. > > So, it probably makes sense to just have: > ASSERT(num < 32); > > ASSERT() is fine here as I don't think that compiler will use incorrect > number during register allocation. I agree. However, the x0 aspect is still odd. Why again is it that struct cpu_user_regs has a field for it, when the register value is always 0? (And tangentially, what's the pregs field there, and what is stack_cpu_regs?) >>> --- /dev/null >>> +++ b/xen/arch/riscv/include/asm/gpr-num.h >>> @@ -0,0 +1,33 @@ >>> +/* SPDX-License-Identifier: GPL-2.0-only */ >>> +#ifndef RISCV_GPR_NUM_H >>> +#define RISCV_GPR_NUM_H >>> + >>> +/* GPR ABI names, in register-number order (x0 .. x31). */ >>> +#define GPR_ABI_NAMES \ >>> + zero, ra, sp, gp, tp, t0, t1, t2, \ >>> + s0, s1, a0, a1, a2, a3, a4, a5, \ >>> + a6, a7, s2, s3, s4, s5, s6, s7, \ >>> + s8, s9, s10, s11, t3, t4, t5, t6 Having looked at struct cpu_user_regs for the response above: How is this macro intended to be kept in sync with struct cpu_user_regs? Yes, the ABI isn't going to change, but (a) still and (b) if later another ABI was introduced, names here and fields there could still easily diverge. >>> +#ifdef __ASSEMBLER__ >>> + >>> + .equ .L_gpr_num, 0 >>> + .irp name, GPR_ABI_NAMES >>> + .equ .L_gpr_num_\name, .L_gpr_num >>> + .equ .L_gpr_num, .L_gpr_num + 1 >>> + .endr >> >> So this is emitted no matter whether a .S file actually uses any of the constants. >> Perhaps okayish, but somewhat wasteful. > > I can move #include inside "#else /* __ASSEMBLER__ */" > in asm/extable.h and it will be enough for now. Or just drop declaration > of .L_gpr_num for assembler code until it will be needed by it. How would either of these address the remark I made? Not every .S file including asm/extable.h will need these constants. Imo this new file wants strictly only including by files which actually need .L_gpr_num_*. Jan