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 AF76BC5320E for ; Tue, 20 Aug 2024 09:14:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=yZa8XNLTFH/TYxB/6ufFQyi9yG0Lr3zYGfPaAE99nzw=; b=PW21p/sUA4fZDdl8jXE4S21sxO Q/A6VIM1PRaqcgc9IAAFHvUhLmKsBhxycfYkvWLJpkr5Tj2v6E6XaDSEMg/VpGUF9A1wbDl51dslN iU+K0d+Lq8LHCVBZZVUTj2bIHns/nU6ui0CD3mVtHfbSjfk4e1OUTzNqNNriZ3p21DzA4l9bLwwS6 +TsrmYSWzv6z+QlASdSxRhfI3BgeJ59KWVyXc5E7TW3FU6OIqcYkpW7MgaYtHU+fLY8AUB8630s+P gdjRYvNsqYTZSzqNCq0r3YQ+8s8ezJG7uxq9396zRm5RVefh1MY8tLwx5fs/9P45rnkZzDc4WaQQX 23x/Yvdg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sgKvz-00000004Veq-1yzA; Tue, 20 Aug 2024 09:13:47 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sgKvG-00000004VWJ-3YLK for linux-arm-kernel@lists.infradead.org; Tue, 20 Aug 2024 09:13:04 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DB16ADA7; Tue, 20 Aug 2024 02:13:25 -0700 (PDT) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3BA6B3F66E; Tue, 20 Aug 2024 02:12:55 -0700 (PDT) Date: Tue, 20 Aug 2024 10:12:47 +0100 From: Mark Rutland To: Tong Tiangen Cc: Catalin Marinas , Will Deacon , Andrew Morton , James Morse , Robin Murphy , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Michael Ellerman , Nicholas Piggin , Andrey Ryabinin , Alexander Potapenko , Christophe Leroy , "Aneesh Kumar K.V" , "Naveen N. Rao" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, wangkefeng.wang@huawei.com, Guohanjun Subject: Re: [PATCH v12 2/6] arm64: add support for ARCH_HAS_COPY_MC Message-ID: References: <20240528085915.1955987-1-tongtiangen@huawei.com> <20240528085915.1955987-3-tongtiangen@huawei.com> <4436d172-c474-8ecd-b5e4-4c21088baf49@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4436d172-c474-8ecd-b5e4-4c21088baf49@huawei.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240820_021303_022791_6F81387B X-CRM114-Status: GOOD ( 39.13 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Aug 20, 2024 at 10:11:45AM +0800, Tong Tiangen wrote: > 在 2024/8/20 1:29, Mark Rutland 写道: > > Hi Tong, > > > > On Tue, May 28, 2024 at 04:59:11PM +0800, Tong Tiangen wrote: > > > For the arm64 kernel, when it processes hardware memory errors for > > > synchronize notifications(do_sea()), if the errors is consumed within the > > > kernel, the current processing is panic. However, it is not optimal. > > > > > > Take copy_from/to_user for example, If ld* triggers a memory error, even in > > > kernel mode, only the associated process is affected. Killing the user > > > process and isolating the corrupt page is a better choice. > > > > > > New fixup type EX_TYPE_KACCESS_ERR_ZERO_ME_SAFE is added to identify insn > > > that can recover from memory errors triggered by access to kernel memory. > > > > > > Signed-off-by: Tong Tiangen [...] > > > diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h > > > index 980d1dd8e1a3..9c0664fe1eb1 100644 > > > --- a/arch/arm64/include/asm/asm-extable.h > > > +++ b/arch/arm64/include/asm/asm-extable.h > > > @@ -5,11 +5,13 @@ > > > #include > > > #include > > > -#define EX_TYPE_NONE 0 > > > -#define EX_TYPE_BPF 1 > > > -#define EX_TYPE_UACCESS_ERR_ZERO 2 > > > -#define EX_TYPE_KACCESS_ERR_ZERO 3 > > > -#define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4 > > > +#define EX_TYPE_NONE 0 > > > +#define EX_TYPE_BPF 1 > > > +#define EX_TYPE_UACCESS_ERR_ZERO 2 > > > +#define EX_TYPE_KACCESS_ERR_ZERO 3 > > > +#define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4 > > > +/* kernel access memory error safe */ > > > +#define EX_TYPE_KACCESS_ERR_ZERO_ME_SAFE 5 > > > > Could we please use 'MEM_ERR', and likewise for the macros below? That's > > more obvious than 'ME_SAFE', and we wouldn't need the comment here. > > Likewise elsewhere in this patch and the series. > > > > To Jonathan's comment, I do prefer these numbers are aligned, so aside > > from the naming, the diff above looks good. > > OK, I also modified other locations to use 'MEM_ERR'. Thanks! [...] > > > diff --git a/arch/arm64/lib/copy_to_user.S b/arch/arm64/lib/copy_to_user.S > > > index 802231772608..2ac716c0d6d8 100644 > > > --- a/arch/arm64/lib/copy_to_user.S > > > +++ b/arch/arm64/lib/copy_to_user.S > > > @@ -20,7 +20,7 @@ > > > * x0 - bytes not copied > > > */ > > > .macro ldrb1 reg, ptr, val > > > - ldrb \reg, [\ptr], \val > > > + KERNEL_ME_SAFE(9998f, ldrb \reg, [\ptr], \val) > > > .endm > > > .macro strb1 reg, ptr, val > > > @@ -28,7 +28,7 @@ > > > .endm > > > .macro ldrh1 reg, ptr, val > > > - ldrh \reg, [\ptr], \val > > > + KERNEL_ME_SAFE(9998f, ldrh \reg, [\ptr], \val) > > > .endm > > > .macro strh1 reg, ptr, val > > > @@ -36,7 +36,7 @@ > > > .endm > > > .macro ldr1 reg, ptr, val > > > - ldr \reg, [\ptr], \val > > > + KERNEL_ME_SAFE(9998f, ldr \reg, [\ptr], \val) > > > .endm > > > .macro str1 reg, ptr, val > > > @@ -44,7 +44,7 @@ > > > .endm > > > .macro ldp1 reg1, reg2, ptr, val > > > - ldp \reg1, \reg2, [\ptr], \val > > > + KERNEL_ME_SAFE(9998f, ldp \reg1, \reg2, [\ptr], \val) > > > .endm > > > .macro stp1 reg1, reg2, ptr, val > > > > These changes mean that regular copy_to_user() will handle kernel memory > > errors, rather than only doing that in copy_mc_to_user(). If that's > > intentional, please call that out explicitly in the commit message. > > Yes. This is the purpose of the modification. If the copy_to_user() > function encounters a memory error, this uaccess affects only the > current process. and only need to kill the current process instead of > the entire kernel panic. Do not add copy_mc_to_user() so that > copy_to_user() can process memory errors. > > I'll add a description in the commit msg next version. Ok; why do powerpc and x86 have separate copy_mc_to_user() implementations, then? [...] > > > +/* > > > + * APEI claimed this as a firmware-first notification. > > > + * Some processing deferred to task_work before ret_to_user(). > > > + */ > > > +static bool do_apei_claim_sea(struct pt_regs *regs) > > > +{ > > > + if (user_mode(regs)) { > > > + if (!apei_claim_sea(regs)) > > > + return true; > > > + } else if (IS_ENABLED(CONFIG_ARCH_HAS_COPY_MC)) { > > > + if (fixup_exception_me(regs) && !apei_claim_sea(regs)) > > > + return true; > > > + } > > > + > > > + return false; > > > +} > > > > Hmm... that'll fixup the exception even if we don't manage to claim a > > the SEA. I suspect this should probably be: > > > > static bool do_apei_claim_sea(struct pt_regs *regs) > > { > > if (apei_claim_sea(regs)) > > return false; > > if (user_mode(regs)) > > return true; > > if (IS_ENABLED(CONFIG_ARCH_HAS_COPY_MC)) > > return !fixup_excepton_mem_err(regs); > > > > return false; > > } > > > > ... unless we *don't* want to claim the SEA in the case we don't have a > > fixup? > > > > Mark. > > > > Yes. My original meaning here is that if not have fixup, panic is > performed in do_sea() according to the original logic, and claim sea is > not required. AFAICT my suggestion doesn't change that; if we don't have a fixup the proprosed do_apei_claim_sea() would return false, and so do_sea() would caryy on to arm64_notify_die(...). I'm specifically asking if we need to avoid calling apei_claim_sea() when we don't have a fixup handler, or if calling that would be fine. One important thing is that if apei_claim_sea() fails to claim the SEA, we'd like to panic(), and in that case it'd be good to have not applied the fixup handler, so that the pt_regs::pc shows where the fault was taken from. Mark.