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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== 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> X-Rspam-User: X-Stat-Signature: tiwj3613emnpiddh1r8xirb1y6mcdsgx X-Rspamd-Queue-Id: 897BAC0026 X-Rspamd-Server: rspam02 X-HE-Tag: 1729867233-554568 X-HE-Meta: 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 m+ZMDhar l99C8wipNL1S8L/nyeBbJ2ov3RGeeGL/xaq+3qns7PCkcsT7TztLpaDT7b2bLxRwg+L1Kjl3CMquEE4vP1PnZeqx/nnUcHZZ349LOwkboXirr2H5vtLAXaYfKf719vOKXdKcBpepMyED5BZhkjSlbpRp+NjTP9F6LwUvBCQDdLB8tgcKXrTs1WpqrNGTAUoOzA62bUzOq3NAoZDlX1A39ikRU3hDVnqCMioTx2lS5Qf8nmYqbeyxWy7NIeW7w0MFtJ5P62ncnnS+u/6SJbc2u8Zsq18P2aiXJzQmCMnlIFb96syOKQlK5BOEN7r+JRWOcq/I0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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