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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F00D3C05027 for ; Tue, 14 Feb 2023 06:43:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231326AbjBNGna (ORCPT ); Tue, 14 Feb 2023 01:43:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37598 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229648AbjBNGn2 (ORCPT ); Tue, 14 Feb 2023 01:43:28 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 66470EB79 for ; Mon, 13 Feb 2023 22:43:27 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id BF167CE1F26 for ; Tue, 14 Feb 2023 06:43:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6C861C433EF; Tue, 14 Feb 2023 06:43:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1676357003; bh=lq4W396FO+Q3Y2AX/3T1BrpLEZNbnz8ryv/Vmo361xs=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=VFCrbqIcsVnE5fUmOjjPNWrBldBZeePy7P0Yz2LYjVZLjKBVTrDsCZh1/XFBLHg4p 1Ql4Wq/1+ylkQvHEV8goFJdarOX0C5r35G6keDIyrMlrMAc/L1IAs67fxxL9f48tMn FhkWOJa5RTDP9ctWVydEKvnWaGujrrLUGyO0NlpMd0Iig5Wlvt1TftfCkO9l/vPfvP AWyBvPlM1EbpIj2xVDK4hRIyp1FP7ZSp/fOQY7Y4mXWcAvqQUqRFoEcFT7O15RfuGW J4sKbRe1zbx+jgHj4n7HKpJ+Ibsb7lZL3CbPWBEbRLpg0h01IwKSg7aX8qY7ZqvdVi PxKV6c9orGOYQ== From: =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= To: Vineet Gupta , Andy Chiu , linux-riscv@lists.infradead.org, palmer@dabbelt.com, anup@brainfault.org, atishp@atishpatra.org, kvm-riscv@lists.infradead.org, kvm@vger.kernel.org Cc: greentime.hu@sifive.com, guoren@linux.alibaba.com, Paul Walmsley , Albert Ou , Heiko Stuebner , Andrew Jones , Lad Prabhakar , Conor Dooley , Jisheng Zhang , Vincent Chen , Guo Ren , Li Zhengyu , Masahiro Yamada , Richard Henderson Subject: Re: [PATCH -next v13 10/19] riscv: Allocate user's vector context in the first-use trap In-Reply-To: <82551518-7b7e-8ac9-7325-5d99d3be0406@rivosinc.com> References: <20230125142056.18356-1-andy.chiu@sifive.com> <20230125142056.18356-11-andy.chiu@sifive.com> <875ycdy22c.fsf@all.your.base.are.belong.to.us> <82551518-7b7e-8ac9-7325-5d99d3be0406@rivosinc.com> Date: Tue, 14 Feb 2023 07:43:21 +0100 Message-ID: <87sff8ags6.fsf@all.your.base.are.belong.to.us> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Vineet Gupta writes: > On 2/7/23 06:36, Bj=C3=B6rn T=C3=B6pel wrote: >>> +bool rvv_first_use_handler(struct pt_regs *regs) >>> +{ >>> + __user u32 *epc =3D (u32 *)regs->epc; >>> + u32 tval =3D (u32)regs->badaddr; >>> + >>> + /* If V has been enabled then it is not the first-use trap */ >>> + if (vstate_query(regs)) >>> + return false; >>> + /* Get the instruction */ >>> + if (!tval) { >>> + if (__get_user(tval, epc)) >>> + return false; >>> + } >>> + /* Filter out non-V instructions */ >>> + if (!insn_is_vector(tval)) >>> + return false; >>> + /* Sanity check. datap should be null by the time of the first-use tr= ap */ >>> + WARN_ON(current->thread.vstate.datap); >>> + /* >>> + * Now we sure that this is a V instruction. And it executes in the >>> + * context where VS has been off. So, try to allocate the user's V >>> + * context and resume execution. >>> + */ >>> + if (rvv_thread_zalloc()) { >>> + force_sig(SIGKILL); >>> + return true; >>> + } >> Should the altstack size be taken into consideration, like x86 does in >> validate_sigaltstack() (see __xstate_request_perm()). > > For a preexisting alternate stack ? Yes. > Otherwise there is no=20 > "configuration" like x86 to cross-check against and V fault implies=20 > large'ish signal stack. > See below as well. > >> Related; Would it make sense to implement sigaltstack_size_valid() for >> riscv, analogous to x86? > > Indeed we need to do that for the case where alt stack is being setup,=20 > *after* V fault-on-first use. > But how to handle an existing alt stack which might not be big enough to= =20 > handle V state ? What I'm getting at is a stricter check at the time of fault (SIGILL/enable V) handling. If the *existing* altstack is not big enough, kill the process -- similar to the rvv_thread_zalloc() handling above. So, two changes: 1. Disallow V-enablement if the existing altstack does not fit a V-sized frame. 2. Sanitize altstack changes when V is enabled. Other than the altstack handling, I think the series is a good state! It would great if we could see a v14 land in -next... Bj=C3=B6rn 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 44F4DC61DA4 for ; Tue, 14 Feb 2023 06:43:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:References :In-Reply-To:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=mpPYnBQU4zJJH+suwiZ3+pxCh15lJW3cs1NbCffNAN8=; b=B+s2eFKbmncxJf BelrQTVNpJuyv7TcxNC601q8ZA0nQ/Svj96Yd/KSJSCjkmimvxBZyGMsXCZMHbdOIlHDECTOwVbuM gYapoosnw66yzOnlaAO/Y7ZaP0FV3j91M1QYlW0UoUDN8VJg3GGpD1nIP/e2ZAmeHBEMttQeTy60q CLK1wSOphL6ZDmxRd099NMAC5/vGJHolJtzZISV7Mqh+RQZoXRundGeIrV8jb7FkC8uMHAAkHN9Rq sovyTfjWW60aVpSHz0+PjXfdm090idjoNgP+51Q1ngKj2AvY9BOpK4aZmhCek75kdIl4CIgXEDz1Q 5mzN4aBTqbRgAe3fkNZg==; 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