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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6b04f9f8343sm5986836d6.126.2024.06.06.06.14.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Jun 2024 06:14:04 -0700 (PDT) Date: Thu, 6 Jun 2024 09:14:01 -0400 From: Peter Xu To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dan Williams , Pasha Tatashin Subject: Re: [PATCH] mm/page_table_check: Fix crash on ZONE_DEVICE Message-ID: References: <20240605212146.994486-1-peterx@redhat.com> <20240605150543.87c81189fa7cb562e73fa0b8@linux-foundation.org> MIME-Version: 1.0 In-Reply-To: <20240605150543.87c81189fa7cb562e73fa0b8@linux-foundation.org> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 2597440020 X-Rspam-User: X-Stat-Signature: uc1p53jobpmnsfoa43ozswgq37ye9iim X-HE-Tag: 1717679647-749855 X-HE-Meta: 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 bz0p3Ztu fR8NI7p0pKWGuDeLHi4BOFDOd/iqnXOdOCi6Zu4kch8C3Nqofx4tOJCVTUyRBUU40qWmOWaHCk75KYZdaen/qLPXPpT3NqLfNY7BgU+3i/Rt9mAlF10QdnzrUoUMR0c5828t5Sh4m/kH/YRo1Z08DKWe2VTjHSV1x5K5Vc0SMxuO1jOKEKS1b5FAlwIy9nyRvJBArOS8eHSZtRZiVyyPvkBdyjjNGneiNPD/4NWs8IGJXd8nxBfoOFKYQSnLqX5px3JDKeyUWRGxuFExkpLynDOQqidaYx3KXYgAe89Pl/MGU2WK2mSCAVNTSF0UhBfYLmCf5XiEeDGIvlWgpSHgyLcZDWjtNjDHiwetX9w/TxhWiLBqDwKxkxDC1ztkkThszd17mEmB3ZZoXZHK1LdhS6yEbRBvFstUCZVdeQWKs5pSkJR0/w86/4hSQSVXXIxiXO5ALk87Zw7FHLT+warB1fqCSkcrnubClMaFZ 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 Wed, Jun 05, 2024 at 03:05:43PM -0700, Andrew Morton wrote: > On Wed, 5 Jun 2024 17:21:46 -0400 Peter Xu wrote: > > > Not all pages may apply to pgtable check. One example is ZONE_DEVICE > > pages: they map PFNs directly, and they don't allocate page_ext at all even > > if there's struct page around. One may reference devm_memremap_pages(). > > > > When both ZONE_DEVICE and page-table-check enabled, then try to map some > > dax memories, one can trigger kernel bug constantly now when the kernel was > > trying to inject some pfn maps on the dax device: > > > > kernel BUG at mm/page_table_check.c:55! > > > > While it's pretty legal to use set_pxx_at() for ZONE_DEVICE pages for page > > fault resolutions, skip all the checks if page_ext doesn't even exist in > > pgtable checker, which applies to ZONE_DEVICE but maybe more. > > Do we have a Reported-by: for this one? Nop, I just hit that when I started to look at the dax issues. > > And a Fixes? It looks like df4e817b7108? Yes that commit should be proper. Thanks, -- Peter Xu