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b=uqXLf/kFl1ZolzQ5qMOzzufmQF402Ru1QwZdJp1B6u4wGJR69WsEhsDP0t0mCFhzT Sz9fWMHNzDNrn0pzUkTiyQTVKziXmvqAnD8lBHY8qTdke7+TrWE5vXu6O9AlShGH6q n7KdcA8RbxpdegBYWXNOYOp0jclQe0CXib5MyvcBU7ZlTMHmCKLHWamZA/NBdZ/V+h Dfohfp4E6ReZTcVL67bGaxIVirIatyk/uZbuI6b/De1ywOCH7o+54fn6C1yqpiRQKp Ue62bxAXdAg8gWTCKppbw4YRTD46Jjo7qXqrCHrX0IKhgr9qYxvGO15058GLEWVu+c evUBu1XpxaJNw== Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 20 Sep 2024 14:44:16 +0300 Message-Id: Cc: , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v13 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> <20240920043027.21907-4-xueshuai@linux.alibaba.com> In-Reply-To: <20240920043027.21907-4-xueshuai@linux.alibaba.com> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 89716140007 X-Stat-Signature: 9iuyr8huwbcjr5bp6qr7ipnnp8upuha7 X-Rspam-User: X-HE-Tag: 1726832661-611522 X-HE-Meta: U2FsdGVkX1/Epu8aEm+m2SnX7iCAWOWAquqAI+62FBEgmK4QsvmLWXmMit9jGA3SBO3ZKa4K41nFNgvGk88GLYMqpPUE7+1gx59D3ml7KwnwQ+14KYSv2BbmfROdl+bVpDsLtduLZI0CuRiEthKUE75fNEwUIlkwShan/CbxCa0/Df1M+v92NSyAHjcWn5Gf55tkj/hX0RsThxn4tiiamy2HIpt5SOYQqMZSWCdZ1AsXyHeDfKPfyLYtXTztUPDkeD194Jcihd01P5mdQszPpma4W9ZRmtRPafF6m6uq4aovkyyh3ucEgF+vDMxPS7vka5b+7fFB3Tf+edLnmsjuyAKuwNCtiDgvOrgSRz9rzpbAUy8+qvKvsYbAjt9wpqVvlTkieZdvChqvtaieN2bko4/icBIV8Y3sHDdZINkdjl/HdHkvvaQwvUCWElM4/IU8owHAbxaZVWgveSbP8sx/ZCYONnuMfUYl+nEckfOGOPZlh7Z111rqVaWFAKgVYBXjzabAnRhz+0dp4C5V6k5A9NR9it+8jkrjVpuHKhFRPt4ChZYhHwCzsBEgqnCc7vwb9hYBQ8m8jVficsZLzCG3BYoJy8Ll97sqgImLd+v7E749Ilsj14KCYWOC7Cw2sbNHMa1Fqs6v8rgzpjE/BOa3aao1udyVbAkygfXm7kiP6u5jDhhwkdYtf4egEcsjr4P25U51scuLitVGjgqYi/RScU3F+8XOf4c8XkPnCG351IWzwd0h0kg8Hx0iMmqoKoOQ+72upbsWZrkg057WwdVqh2f8kTRsUmHRFsLRLNtTQ8ZCT4XHIB36bhvXNeq3vC9RGfVlS/d989e8uDVzgV+PrLUEA1f8+wT4JMu3PQ2vazeucxP87dohJSefYTNWA/jcihoDGZqQjovPn6f+vhkp58x5YUKGgHLFJSulHKCPMhzpbrhiSQ0Tl7RzPaBX+2KfeKCwLebOFfS7vsjcxW2 Lnb4DUb8 0Ku9xJLDtIcCMSlJdQ4BGylDETFEvsNKwvhqwf8XsXPrk5QWoKDgFVMczR8wxSZPtDk4POfrMhVpwkT37kJxrYoqdwcf5jb2KnuFPzktUllLqGQAUXm5JuFw8tqKB1e6B7ftPbXZ9JEhRdVSwOJm3glnOz4MiBRxR3tsbIobAn2jh9L+HIWTAI4i6pQ+C7cbdwkWtLygLNq84HyqTo2ud4trEqCSyQPpGVHoL7z2Qgy3Tduj1sbBqpnPycvo8mLPafsvTS8y9QAm7H01PO1rNoyuStGMXf7lUspnRAGNWYFRQC9c= 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 Fri Sep 20, 2024 at 7:30 AM EEST, Shuai Xue wrote: > The memory uncorrected error could be signaled by asynchronous interrupt > (specifically, SPI in arm64 platform), e.g. when an error is detected by > a background scrubber, or signaled by synchronous exception > (specifically, data abort excepction in arm64 platform), e.g. when a CPU > 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. > > 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: > > - 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 > > Issue 1: send wrong si_code in early_kill mode > > Since commit a70297d22132 ("ACPI: APEI: set memory failure flags as > MF_ACTION_REQUIRED on synchronous events")', the flag MF_ACTION_REQUIRED > could be used to determine whether a synchronous exception occurs on > ARM64 platform. When a synchronous exception is detected, the kernel is > 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. > > 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. > > To reproduce this problem: > > #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 er= ror > #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 > > The si_code (code 5) from einj_mem_uc indicates that it is BUS_MCEERR_AO > error and it is not fact. > > After this patch: > > # 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 er= ror > #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 > > The si_code (code 4) from einj_mem_uc indicates that it is BUS_MCEERR_AR > error as we expected. > > Issue 2: a synchronous error infinite loop > > If a user-space process, e.g. devmem, a poisoned page which has been set > 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. > > To reproduce this problem: > > # STEP 1: inject an UCE error, and kernel will set HWPosion flag for re= lated 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 > > # STEP 2: access the same page and it will trigger a synchronous error = infinite loop > devmem 0x4092d55b400 > > 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. > > 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(-) > > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c > index 93eb11482832..60d8044f14d1 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 context = that > - * triggered the notification. > + * struct 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(). > */ > -static void ghes_kick_task_work(struct callback_head *head) > +struct task_work { > + struct callback_head twork; > + u64 pfn; > + int flags; > +}; I'd rename this as ghes_task_work. It is too generic name IMHO, easily confused with task_work.h definitions. BR, Jarkko