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Sat, 22 Jul 2023 20:37:54 -0700 (PDT) MIME-Version: 1.0 References: <20230722231508.1030269-1-pasha.tatashin@soleen.com> <20230722231508.1030269-3-pasha.tatashin@soleen.com> <52c883a3-5951-b298-cae4-a46fa0619411@infradead.org> In-Reply-To: <52c883a3-5951-b298-cae4-a46fa0619411@infradead.org> From: Pasha Tatashin Date: Sat, 22 Jul 2023 23:37:10 -0400 Message-ID: Subject: Re: [PATCH v2 2/3] doc/vm: add information about page_table_check warn_on behavior To: Randy Dunlap Cc: akpm@linux-foundation.org, corbet@lwn.net, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, rick.p.edgecombe@intel.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: A456D80004 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: gcq3oauq8jdyfbti1iuxj3w3astwec8e X-HE-Tag: 1690083475-241660 X-HE-Meta: U2FsdGVkX1/Ab8d1z7JdKnecmtWs4/Ou2KuHVjSY7lEbZmb8VFcdcdVExGHWcELjSnO33Xgg1Qr25bl6N76SftHi7IHjMImvCoxwj2rkmqmQOsEYvZhKrizs0v1oM32sCM6mP89+mjH4AH/wcDKXmN8iGYx1U1iY9oLRhqssIZk8fTwXxTj4rksujnuCmz7ej42dk7X5ws0OkdfsFFoXwfsjX0HFN4lhQEv65M50B5EwI18LPYYFbJ6XF7LnA6vZ9BhWmR4ZJi52AVda8WqhiClgYsorHI1gcK3CcOupnRVIUmRoyGASTdBgCaFZoCbRL+Vyad8JlXQiS16y25VDCe4Vsj7j0oHlGgAnBPc0viNPsPAg2IzXJZ4bnWYfOO1xtawPVYWADFbznEoH3A+bTKg3sFKZAXtmCD7K4U9sMhBo5YOV7P1CLYX7xhQl5E9wop/FFkb7Vi5W6upnPyCZVOKEyv7Tk447pAUlmmE9TjgMmSEErRBT0jM1c/Y6G7Zq5VFP+ETrrJFJtUXXUkkRP5lyyGJyoo6HlVfwtbwgMi5eqgIu7zuW196hDprIKD8HmVklVdl4xqwJjmwFf9/tSyekLoT7+BDpCjS2TVwxZYiNFyDVNEvIkc05ZnmAekuGGRbLkfQhQY/g+sBgSAt4oSs48xr0kysI23Jdt/h62m9xKhP+P1c5np1Ut8VPS+EFj83UDbJ2z6vcm6cTB3HgGfLhplxpO1H/iOk1U4JYyNYaBB9VHFubJjLZ6G9jo9IzXQ4auUlpAxTEEQgajS4A4mZBUqI6S4w4ThFoLhQtuJvrMCtbLaSMTdq47nu4gmGPFvfqLo3+I/ju2+98jdHu3ACzOkYhtCIzCoaP5j0D0vLMBgenuQ09Zm/snhe4LA2L4ordh9Zhq064of3kDrhkbTQRA9UuEK6I7kaqqq94xqV1aENSkYG4tFaO0qwFUruajjH4xYZImbWlQpeVac3 jA38+NqQ 9CatgLS2HhC8U4qmHDawGO5AIl6/4Ik78/APvJgP+lseYUrrE6J4pYN99s8UVv7fIOYDHTGJDTDJaIkPFown8yMrrd116O8Q7t2WTgxGkwxGEKIm/8bw/kl3yIPxB9WOCJA+CrRs0P9jBs42GZ7Xib0z6IWtC5KMTkGPNm1ZxH8R4cKf143IPkUzWwFBFpLpXNS5a4iDoLMC/96MFEcSUDmlS/vl3UfJFsGMk3Oo1a3h9UqwUZuw0JzmeOjNq61gobtf+WgljReV9fBFH1fpIHih7UfjbTWzeWnCb9nk4ljoFzSpQg1TtCdr454nuG/LBTqJGAbAXjlEDCgCwkOOwAyvi0YkEKmSbWQLSSuADhSkJ2nQ= 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 Sat, Jul 22, 2023 at 7:59=E2=80=AFPM Randy Dunlap wrote: > > Hi-- > > On 7/22/23 16:15, Pasha Tatashin wrote: > > The default behavior of page table check was changed from panicking > > kernel to printing a warning. > > > > Add a note how to still panic the kernel when error is detected. > > > > Signed-off-by: Pasha Tatashin > > --- > > Documentation/mm/page_table_check.rst | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/Documentation/mm/page_table_check.rst b/Documentation/mm/p= age_table_check.rst > > index c12838ce6b8d..f534c80ee9c9 100644 > > --- a/Documentation/mm/page_table_check.rst > > +++ b/Documentation/mm/page_table_check.rst > > @@ -14,13 +14,14 @@ Page table check performs extra verifications at th= e time when new pages become > > accessible from the userspace by getting their page table entries (PT= Es PMDs > > etc.) added into the table. > > > > -In case of detected corruption, the kernel is crashed. There is a smal= l > > +In case of detected corruption, a warning is printed. There is a small > > performance and memory overhead associated with the page table check.= Therefore, > > it is disabled by default, but can be optionally enabled on systems w= here the > > extra hardening outweighs the performance costs. Also, because page t= able check > > is synchronous, it can help with debugging double map memory corrupti= on issues, > > by crashing kernel at the time wrong mapping occurs instead of later = which is > > -often the case with memory corruptions bugs. > > +often the case with memory corruptions bugs. In order to crash kernel = sysctl > > +panic_on_warn should be set to 1. > > Better as: > In order to crash the kernel, the sysctl panic_on_warn should be set > to 1. Will update in the next version. Thanks, Pasha >