From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id C831E18B46E for ; Tue, 20 Aug 2024 09:13:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724145183; cv=none; b=amRGb52dPEzI+rR80AFYY3dIAAvQHbRxlJhUihW68PCMnfjVi+rNLk7LMMDdmUgIqnx3ggE/ffwJFQmejH7Nh5/eErhRAQydhpWv+6IT8bVAguHuznzeNjUsPoMu3OZCa0YGQXyJrk8+ONANKtEegraFANYl+MDeqzEsENPpjfs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724145183; c=relaxed/simple; bh=eMQ7xAnJ5JEFjPyimxBz7Ll/eyTDi2uPgp4ViH8BATI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OPkjmPjEQR/v3t8oAQXwMGarm/jLhu9Er7NlVh8WID3f1Hl8sibi1v1vBs4dg8J1JER9Z8H39CH5xLfJRmtZ1D1qbPr0d1K95zKAC4iPCn4vL/dN+C0lO8d9UvD856v3gNkxHek3sNMLTrSFpJN3QPBYDxnsaIdDCYOkAqMUYKc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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> 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.