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h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=HUvp73ijpQYic3gRaURF4D3OSbULFRnhHTQh5Kic03/1ZO+YRcy/dsR5zGvdl0hPH znrLxImKjFswYuAqJUYOCBDVBWcDUna+fcIbdRRe3TQSt469Z2xLrtt65RTvOVrth0 Gd+MaGyE61KwnWtvs7ClEhgwGfH73C8fUoBBK1k8= Date: Wed, 5 Jun 2024 15:05:43 -0700 From: Andrew Morton To: Peter Xu 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: <20240605150543.87c81189fa7cb562e73fa0b8@linux-foundation.org> In-Reply-To: <20240605212146.994486-1-peterx@redhat.com> References: <20240605212146.994486-1-peterx@redhat.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 61C40A0012 X-Rspam-User: X-Rspamd-Server: rspam12 X-Stat-Signature: spy49t93eyf3qmcdhdancxniacc5rcmz X-HE-Tag: 1717625149-998162 X-HE-Meta: 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 QQQCMzE3 uOqDEZ0uxSOU3Jcii+NweBaHPM1qfeaJHzi+wXbe00IQL7SQfVWrMHNounHUgHbjDmuBydnzewlu27Rialzz/cwy7vKsKlBZny3CRlqA9DIm4bM7SdUyX5sr5WrYHbWOzCwhst2/yFDmHBAJjkXsZBUsJ1yd+eE0Ic6NjNqkfcTgNSgQQ4omEu+jMtRFxOk28XAI60zQAawYLwpjeYu3cVQr6Rh8YgVWx0EVPp2kFpMqkMBSWI+nnVVud4mPWX8zOYWUWbEx9ZpdVPl5E9dV1LCmkAMDP/9fJ8zU7Hze6hPeWLYU= 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, 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? And a Fixes? It looks like df4e817b7108?