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Thu, 10 Jul 2025 09:47:49 -0700 (PDT) Received: from p183 ([46.53.250.196]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ae6e8264663sm157214966b.87.2025.07.10.09.47.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Jul 2025 09:47:49 -0700 (PDT) Date: Thu, 10 Jul 2025 19:47:47 +0300 From: Alexey Dobriyan To: Vlastimil Babka Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Subject: Re: [PATCH] mm: implement "memory.oops_if_bad_pte=1" boot option Message-ID: <1e49cfaf-4669-4b59-afdb-cc872dbcc950@p183> References: <4e1b7d2d-ed54-4e0a-a0a4-906b14d9cd41@p183> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 64609180005 X-Stat-Signature: g5fet3t16radhk44zs1tpi7wocyqe4ad X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1752166071-135920 X-HE-Meta: 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 dV1m+Zbq 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 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 Thu, Jul 10, 2025 at 09:35:41AM +0200, Vlastimil Babka wrote: > On 7/9/25 20:10, Alexey Dobriyan wrote: > > Implement > > > > memory.oops_if_bad_pte=1 > > > > boot option which oopses the machine instead of dreadful > > > > BUG: Bad page map in process > > > > message. > > > > This is intended > > for people who want to panic at the slightest provocation and > > for people who ruled out hardware problems which in turn means that > > delaying vmcore collection is counter-productive. > > > > Linux doesn't (never?) panicked on PTE corruption and even implemented > > ratelimited version of the message meaning it can go for minutes and > > even hours without anyone noticing which is exactly the opposite of what > > should be done to facilitate debugging. > > > > Not enabled by default. > > > > Not advertised. > > > > Signed-off-by: Alexey Dobriyan > > Could we just reuse the existing panic_on_oops? Would anyone want to panic > in this particular without the others, or vice versa? Yes, it is supposed to be used with panic_on_oops=1, otherwise lot of innocent processes might die. I'll rerhrase the comment. > > +/* > > + * Oops instead of printing "Bad page map in process" message and > > + * trying to continue. > > + */ > > +static bool oops_if_bad_pte __ro_after_init = false; > > +module_param(oops_if_bad_pte, bool, 0444); > > + > > /* > > * This function is called to print an error when a bad pte > > * is found. For example, we might have a PFN-mapped pte in > > @@ -490,6 +498,13 @@ static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss) > > static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr, > > pte_t pte, struct page *page) > > { > > + /* > > + * This line is a formality to collect vmcore ASAP. Real bug > > + * (hardware or software) happened earlier, current registers and > > + * backtrace aren't interesting. > > + */ > > + BUG_ON(oops_if_bad_pte);