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From: Naoya Horiguchi To: David Hildenbrand Cc: linux-mm@kvack.org, Andrew Morton , Alistair Popple , Peter Xu , Mike Kravetz , Konstantin Khlebnikov , Bin Wang , Yang Shi , Naoya Horiguchi , linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] mm, pagemap: expose hwpoison entry Message-ID: <20211004143228.GA1545442@u2004> References: <20211004115001.1544259-1-naoya.horiguchi@linux.dev> <258d0ddb-6c82-0c95-a15e-b085b59d2142@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <258d0ddb-6c82-0c95-a15e-b085b59d2142@redhat.com> X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: naoya.horiguchi@linux.dev X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 46891B000BCC X-Stat-Signature: w4jg9miayu81y3g64zajspp5ztq9xxnr Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=ab9jun9D; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf24.hostedemail.com: domain of naoya.horiguchi@linux.dev designates 188.165.223.204 as permitted sender) smtp.mailfrom=naoya.horiguchi@linux.dev X-HE-Tag: 1633357959-371404 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: On Mon, Oct 04, 2021 at 01:55:30PM +0200, David Hildenbrand wrote: > On 04.10.21 13:50, Naoya Horiguchi wrote: > > From: Naoya Horiguchi > > > > A hwpoison entry is a non-present page table entry to report > > memory error events to userspace. If we have an easy way to know > > which processes have hwpoison entries, that might be useful for > > user processes to take proper actions. But we don't have it now. > > So make pagemap interface expose hwpoison entries to userspace. > > Noting that this is only a way to inspect hwpoison set for private anonymous > memory. You cannot really identify anything related to shared memory. > > Do you also handle private hugetlb pages? I think yes. As long as hugepages are mmap()ed, we should be able to identify them with hwpoison entry (even if used via private/shared mapping). > > > > > Hwpoison entry for hugepage is also exposed by this patch. The below > > example shows how pagemap is visible in the case where a memory error > > hit a hugepage mapped to a process. > > > > $ ./page-types --no-summary --pid $PID --raw --list --addr 0x700000000+0x400 > > voffset offset len flags > > 700000000 12fa00 1 ___U_______Ma__H_G_________________f_______1 > > 700000001 12fa01 1ff ___________Ma___TG_________________f_______1 > > 700000200 12f800 1 __________B________X_______________f______w_ > > 700000201 12f801 1 ___________________X_______________f______w_ // memory failure hit this page > > 700000202 12f802 1fe __________B________X_______________f______w_ > > > > The entries with both of "X" flag (hwpoison flag) and "w" flag (swap > > flag) are considered as hwpoison entries. So all pages in 2MB range > > are inaccessible from the process. We can get actual error location > > by page-types in physical address mode. > > > > $ ./page-types --no-summary --addr 0x12f800+0x200 --raw --list > > offset len flags > > 12f800 1 __________B_________________________________ > > 12f801 1 ___________________X________________________ > > 12f802 1fe __________B_________________________________ > > > > Signed-off-by: Naoya Horiguchi > > --- > > fs/proc/task_mmu.c | 41 ++++++++++++++++++++++++++++++++--------- > > include/linux/swapops.h | 13 +++++++++++++ > > tools/vm/page-types.c | 7 ++++++- > > 3 files changed, 51 insertions(+), 10 deletions(-) > > > Please also update the documentation located at > > Documentation/admin-guide/mm/pagemap.rst I will do this in the next post. Thanks, Naoya Horigcuhi