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b=cpOf350q1+IqKbjq3pAaHeVGWsdV2XTQIVpzRCzS5t+71aK85iZ/VSu+PQs0YIAtq QTzbVeLMZ7h7PO+YudkRqENz+QtL8biLtdQ5ZoY94rKhWfrf/38jl+/iz7QtIMc4hK pMPLdl9EY4aYBw/uNdoe7yF2uZaLuDYv6fOBug3bRtzB7Aek5ikndYSLeSSXuq37Pp ZY3jDxwC8bCuyK1sDrwnLwYI4079YamJ3eVvgFf16V5EELUXKPFBfFUSGjybGKU3Z0 2bVoTh2vNwl6q5KhVzSr0SC+P8I3XSyrK7JpWcJk7l56gtBbWlgA1kV6Oei0e9xRLz 97qvr0v/yuLgA== Message-ID: <494d436c-e3b3-4b65-8a6c-1059d9f468d4@kernel.org> Date: Fri, 2 Oct 2026 14:19:00 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: don't ioremap COWed anon pages in generic_access_phys() To: "Lorenzo Stoakes (ARM)" Cc: Nguyen Ngoc Thang , akpm@linux-foundation.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, peterx@redhat.com, dave.hansen@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, syzbot+49b1021becba70c1f3f6@syzkaller.appspotmail.com References: <699ae98c.050a0220.340abe.0d31.GAE@google.com> <20261001152524.171115-1-ngocthang2710.1999@gmail.com> <32fe40e2-854a-47ec-9d95-93e23f9a7af4@kernel.org> <9d43234f-93cb-4c86-a2a6-a3cdebf48f3b@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 3BC671C0009 X-Stat-Signature: 171jrzd758ir7o6okeyi7gkz97emhb6q X-Rspam-User: X-HE-Tag: 1790943548-240819 X-HE-Meta: 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 9rxMCjxH eh/KZcCIdriXhEv7xcXBTEEF40P1Z46HJ6LszyHmVoOe60Tll6ogZw78XH2uigYwQ0TO9zq/EkhPmjGNaJhWUE36Lj4Dk2jlhgykPBwnmRJ/L2HIaNRECFrV+Dq0BO4zdb97+kApuNr+v0fgfrTtFMVVnyLPkZ6Ns7ZjmDfFrLgSDrB8fYpQyzW0uXAB7+AqehXNOEmvyHLqtI8EAIchQoXXAo8+BJj2lG59zoznTgMae9LmnqrBnwML24PA1+gqgzii1vzLQu4dhCziIXtPOwOGMQ7uaW+UNvs0ldTPvyMiXUGVsCTuGCJJ6i8VTuj0bHj/Rbbt4QTEfMIN9xYEYmIkgVXz9MXzIIptsWSsfpytxTA6TjOcUMxwM6DFDeKIkBHlPP1DkHhA4gkmfCCdqyKjsK1sc+U5GNJITigEBuFUjcN3IQr8KVmKuA+QPkjnegYG1 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/2/26 12:09, Lorenzo Stoakes (ARM) wrote: > On Fri, Oct 02, 2026 at 12:04:27PM +0200, David Hildenbrand (Arm) wrote: >> On 10/2/26 12:02, David Hildenbrand (Arm) wrote: >>> >>> Yes, I'll take care of it. >>> >>> [...] >>> >>> After sending this yesterday, I concluded that we can do this cleaner: just have >>> >>> bool normal_page; >>> >>> (naming suggestions?) >>> >>> that express that this is something refcounted with a struct page, like >>> documented for vm_normal_page(). >> >> Hmm, have to think about that once more, regarding VM_IO and if there are some >> cases that would actually have to work in generic_access_phys(). > > Well, my series at least makes it easier to reason about VMA_IO_BIT! > > Though not sure if it really touches PFN map cases specifically. I'm more concerned about someone using this function on VM_MIXEDMAP | VM_IO with a memory page that has a struct page but is actually not memory. So we could get something that vm_normal_page() would flag but generic_access_phys() could actually read ... I'll have to explore the generic_access_phys() users once more. All way to complicated (and you series improves things). -- Cheers, David