From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) (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 F31192046AD; Wed, 12 Feb 2025 08:09:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.187 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739347759; cv=none; b=kU4ncv6306x7ap6DQFePBir6DBIAv4MkUgJWzJL0AmYL7koJYSHy1SzZUv/xoYX5R+xmov04Ey1SsOi3TqZRcXNZ6lvou7sMrPmqaZFeFTiFcp/7EQ4yIy3d5PcxEyhGGY1GPOBrn77S5SlnoSnvcZ9qOXm+GBlBYygN+V5AtcA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739347759; c=relaxed/simple; bh=Hswue5MGF5m27Goc5Gy8v6ReichRB1wMgt8PbHdHc2s=; h=Subject:To:CC:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=Ip12zbsTYqHmJppesnFnFa8q3Ez/OaXXaMrmKle1fyDJRs4+NfWWns7YfPg1i8yIvdXYoNlV3Pteq0h4snx6hGOb3rpxM8BPvz3UPBtw2uqsSc/53dH/HagNkYgpB/vaORRysE3NPgsS45uhVoQWdEd12qGECFNf/LGRCQXOSmY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.187 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.48]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4Yt9q95D9MzkXN3; Wed, 12 Feb 2025 16:05:41 +0800 (CST) Received: from kwepemd200019.china.huawei.com (unknown [7.221.188.193]) by mail.maildlp.com (Postfix) with ESMTPS id 3251B1802D0; Wed, 12 Feb 2025 16:09:14 +0800 (CST) Received: from [10.173.127.72] (10.173.127.72) by kwepemd200019.china.huawei.com (7.221.188.193) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 12 Feb 2025 16:09:13 +0800 Subject: Re: [PATCH v1 4/4] mm/hwpoison: Fix incorrect "not recovered" report for recovered clean pages To: Shuai Xue CC: , , , , , , , , , , , , , References: <20250211060200.33845-1-xueshuai@linux.alibaba.com> <20250211060200.33845-5-xueshuai@linux.alibaba.com> From: Miaohe Lin Message-ID: <5f116840-60df-c6d9-d7ff-dcf1dce7773f@huawei.com> Date: Wed, 12 Feb 2025 16:09:12 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 Precedence: bulk X-Mailing-List: linux-edac@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20250211060200.33845-5-xueshuai@linux.alibaba.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemd200019.china.huawei.com (7.221.188.193) On 2025/2/11 14:02, Shuai Xue wrote: > When an uncorrected memory error is consumed there is a race between > the CMCI from the memory controller reporting an uncorrected error > with a UCNA signature, and the core reporting and SRAR signature > machine check when the data is about to be consumed. > > If the CMCI wins that race, the page is marked poisoned when > uc_decode_notifier() calls memory_failure(). For dirty pages, > memory_failure() invokes try_to_unmap() with the TTU_HWPOISON flag, > converting the PTE to a hwpoison entry. However, for clean pages, the > TTU_HWPOISON flag is cleared, leaving the PTE unchanged and not converted > to a hwpoison entry. Consequently, for an unmapped dirty page, the PTE is > marked as a hwpoison entry allowing kill_accessing_process() to: > > - call walk_page_range() and return 1 > - call kill_proc() to make sure a SIGBUS is sent > - return -EHWPOISON to indicate that SIGBUS is already sent to the process > and kill_me_maybe() doesn't have to send it again. > > Conversely, for clean pages where PTE entries are not marked as hwpoison, > kill_accessing_process() returns -EFAULT, causing kill_me_maybe() to send a > SIGBUS. > > Console log looks like this: > > Memory failure: 0x827ca68: corrupted page was clean: dropped without side effects > Memory failure: 0x827ca68: recovery action for clean LRU page: Recovered > Memory failure: 0x827ca68: already hardware poisoned > mce: Memory error not recovered > > To fix it, return -EHWPOISON if no hwpoison PTE entry is found, preventing > an unnecessary SIGBUS. Thanks for your patch. > > Fixes: 046545a661af ("mm/hwpoison: fix error page recovered but reported "not recovered"") > Signed-off-by: Shuai Xue > --- > mm/memory-failure.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index 995a15eb67e2..f9a6b136a6f0 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -883,10 +883,9 @@ static int kill_accessing_process(struct task_struct *p, unsigned long pfn, > (void *)&priv); > if (ret == 1 && priv.tk.addr) > kill_proc(&priv.tk, pfn, flags); > - else > - ret = 0; > mmap_read_unlock(p->mm); > - return ret > 0 ? -EHWPOISON : -EFAULT; > + > + return ret >= 0 ? -EHWPOISON : -EFAULT; IIUC, kill_accessing_process() is supposed to return -EHWPOISON to notify that SIGBUS is already sent to the process and kill_me_maybe() doesn't have to send it again. But with your change, kill_accessing_process() will return -EHWPOISON even if SIGBUS is not sent. Does this break the semantics of -EHWPOISON? BTW I scanned the code of walk_page_range(). It seems with implementation of hwpoison_walk_ops walk_page_range() will only return 0 or 1, i.e. always >= 0. So kill_accessing_process() will always return -EHWPOISON if this patch is applied. Correct me if I miss something. Thanks. .