From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E3EF91FB89A; Fri, 25 Oct 2024 14:40:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729867257; cv=none; b=M/Gy4NtPGO/82MAB5dl8+ZhxOc4hxZJCWuaaMjt4Q4wsC7VCdRwE63dJpbuJQKvqm3BTdfRixuieSQ7cVZLyUW/07Y5RFUt1IXn5xJPeaCjH4U0HUCACT4tSmJ2ZmVNcYlQIRzJmOjOnO7uLXdpCWx5uVUcGkUdAlPVyP9mlBHI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729867257; c=relaxed/simple; bh=dsMthO8Jrb9+1L6ZnDBu1t1OOQmY7jYi7dCIH4VZXdU=; h=Mime-Version:Content-Type:Date:Message-Id:Cc:Subject:From:To: References:In-Reply-To; b=LSyyhzggLpzzD3dgSDimIdYxRq6ahFzgNo4A8I+NuPtyQA7UeQnWYJyWmwrbTXxNabqD7mEkRMhJSxRs7kjOBon9wxqkSy9ZkBbHNUDmv8eMzKQg0yNErhxRw4vgvgV96u0gbkYhdxWTL805znLqEHzWUgR1SFe3GKWadqs2PxQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DsLuE4Yu; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DsLuE4Yu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C79BFC4CEC3; Fri, 25 Oct 2024 14:40:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729867256; bh=dsMthO8Jrb9+1L6ZnDBu1t1OOQmY7jYi7dCIH4VZXdU=; h=Date:Cc:Subject:From:To:References:In-Reply-To:From; b=DsLuE4YuLKTOMLwG4QbYcC/9yEVkwhUZJSvX6byCliyWU1yve4qV6bXccnRnvPJjy hQt9TUaaD7vnPRgsNPSzA3knTTqaiRHdpAtWkgBqS3hwh5QYRN+DbjGSEPva2RuCai S6ywofDYDrnJ+cXFONwgAVuS0pjNLNS/pXX0O3fciG6Gin4qYttjqZf49GswGeVLQJ DIrSm19K/gfKrz+D7PFEVz8ZPZnZb4oJYVv2REqZnDHGgzX8ISatwGSkevd3Vz9wDK bZb70FzWq0oht19nQCS1hq2gcSqpV5A+b4J84N48CQCj1MggHe/KcTucXhYFuNf0x+ rio8u6IbkoRCQ== Precedence: bulk X-Mailing-List: linux-edac@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 25 Oct 2024 17:40:52 +0300 Message-Id: Cc: , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v14 3/3] ACPI: APEI: handle synchronous exceptions in task work From: "Jarkko Sakkinen" To: "Shuai Xue" , , , , , , , , , , , , , , , , , X-Mailer: aerc 0.18.2 References: <20221027042445.60108-1-xueshuai@linux.alibaba.com> <20241014084240.18614-4-xueshuai@linux.alibaba.com> <05a8d26b-b023-426f-879c-7d33be4a6406@linux.alibaba.com> In-Reply-To: <05a8d26b-b023-426f-879c-7d33be4a6406@linux.alibaba.com> On Tue Oct 22, 2024 at 4:11 AM EEST, Shuai Xue wrote: > Hi, Jarkko, > > > =E5=9C=A8 2024/10/14 16:42, Shuai Xue =E5=86=99=E9=81=93: > > The memory uncorrected error could be signaled by asynchronous interrup= t > > (specifically, SPI in arm64 platform), e.g. when an error is detected b= y > > a background scrubber, or signaled by synchronous exception > > (specifically, data abort excepction in arm64 platform), e.g. when a CP= U > > tries to access a poisoned cache line. Currently, both synchronous and > > asynchronous error use memory_failure_queue() to schedule > > memory_failure() exectute in kworker context. > >=20 > > As a result, when a user-space process is accessing a poisoned data, a > > data abort is taken and the memory_failure() is executed in the kworker > > context: > >=20 > > - will send wrong si_code by SIGBUS signal in early_kill mode, and > > - can not kill the user-space in some cases resulting a synchronous > > error infinite loop > >=20 > > Issue 1: send wrong si_code in early_kill mode > >=20 > > Since commit a70297d22132 ("ACPI: APEI: set memory failure flags as > > MF_ACTION_REQUIRED on synchronous events")', the flag MF_ACTION_REQUIRE= D > > could be used to determine whether a synchronous exception occurs on > > ARM64 platform. When a synchronous exception is detected, the kernel i= s > > expected to terminate the current process which has accessed poisoned > > page. This is done by sending a SIGBUS signal with an error code > > BUS_MCEERR_AR, indicating an action-required machine check error on > > read. > >=20 > > However, when kill_proc() is called to terminate the processes who have > > the poisoned page mapped, it sends the incorrect SIGBUS error code > > BUS_MCEERR_AO because the context in which it operates is not the one > > where the error was triggered. > >=20 > > To reproduce this problem: > >=20 > > #sysctl -w vm.memory_failure_early_kill=3D1 > > vm.memory_failure_early_kill =3D 1 > >=20 > > # STEP2: inject an UCE error and consume it to trigger a synchronous= error > > #einj_mem_uc single > > 0: single vaddr =3D 0xffffb0d75400 paddr =3D 4092d55b400 > > injecting ... > > triggering ... > > signal 7 code 5 addr 0xffffb0d75000 > > page not present > > Test passed > >=20 > > The si_code (code 5) from einj_mem_uc indicates that it is BUS_MCEERR_A= O > > error and it is not fact. > >=20 > > After this patch: > >=20 > > # STEP1: enable early kill mode > > #sysctl -w vm.memory_failure_early_kill=3D1 > > vm.memory_failure_early_kill =3D 1 > > # STEP2: inject an UCE error and consume it to trigger a synchronous= error > > #einj_mem_uc single > > 0: single vaddr =3D 0xffffb0d75400 paddr =3D 4092d55b400 > > injecting ... > > triggering ... > > signal 7 code 4 addr 0xffffb0d75000 > > page not present > > Test passed > >=20 > > The si_code (code 4) from einj_mem_uc indicates that it is BUS_MCEERR_A= R > > error as we expected. > >=20 > > Issue 2: a synchronous error infinite loop > >=20 > > If a user-space process, e.g. devmem, a poisoned page which has been se= t > > HWPosion flag, kill_accessing_process() is called to send SIGBUS to the > > current processs with error info. Because the memory_failure() is > > executed in the kworker contex, it will just do nothing but return > > EFAULT. So, devmem will access the posioned page and trigger an > > excepction again, resulting in a synchronous error infinite loop. Such > > loop may cause platform firmware to exceed some threshold and reboot > > when Linux could have recovered from this error. > >=20 > > To reproduce this problem: > >=20 > > # STEP 1: inject an UCE error, and kernel will set HWPosion flag for= related page > > #einj_mem_uc single > > 0: single vaddr =3D 0xffffb0d75400 paddr =3D 4092d55b400 > > injecting ... > > triggering ... > > signal 7 code 4 addr 0xffffb0d75000 > > page not present > > Test passed > >=20 > > # STEP 2: access the same page and it will trigger a synchronous err= or infinite loop > > devmem 0x4092d55b400 > >=20 > > To fix above two issues, queue memory_failure() as a task_work so that = it runs in > > the context of the process that is actually consuming the poisoned data= . > >=20 > > Signed-off-by: Shuai Xue > > Tested-by: Ma Wupeng > > Reviewed-by: Kefeng Wang > > Reviewed-by: Xiaofei Tan > > Reviewed-by: Baolin Wang > > --- > > drivers/acpi/apei/ghes.c | 78 +++++++++++++++++++++++----------------= - > > include/acpi/ghes.h | 3 -- > > include/linux/mm.h | 1 - > > mm/memory-failure.c | 13 ------- > > 4 files changed, 45 insertions(+), 50 deletions(-) > >=20 > > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c > > index f2ee28c44d7a..95e9520eb803 100644 > > --- a/drivers/acpi/apei/ghes.c > > +++ b/drivers/acpi/apei/ghes.c > > @@ -467,28 +467,42 @@ static void ghes_clear_estatus(struct ghes *ghes, > > } > > =20 > > /* > > - * Called as task_work before returning to user-space. > > - * Ensure any queued work has been done before we return to the contex= t that > > - * triggered the notification. > > + * struct ghes_task_work - for synchronous RAS event > > + * > > + * @twork: callback_head for task work > > + * @pfn: page frame number of corrupted page > > + * @flags: work control flags > > + * > > + * Structure to pass task work to be handled before > > + * returning to user-space via task_work_add(). > > */ > > > Do you have any futer comments about this patch? Any comments are > welcomed. If not, are you happy to explictly give the reveiwed-by tag? Sorry I've been busy switching to a new job. I read this now through and both commit messages and the code changes look sane to me so I guess I don't have any problem with that: Reviewed-by: Jarkko Sakkinen > > Best Regard, > Shuai BR, Jarkko