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AJvYcCV0dxAKuasPoN0LYrcxz5CsbNoShtQWunG+/8BY+UUHbB0vWqfUtIYYLzmjZX0K+x14fXf0aYln38VEiPxclaMjt1E= X-Gm-Message-State: AOJu0Yyw5turpTyrasaMJly9xDoInotkcaqtxcDOXuYu6ZRyuqdVpeVa ekDz5unKqv4AuO3dLYazBfGaPjC1+5zIZB2AvRqs7uZp9TFr/q9fQT7WvUuKdN8j2wf3jJ2enoh hCw== X-Google-Smtp-Source: AGHT+IEiVhcjMIh5HUWd1g2HbFSvaK6Ja8HiHcoC9dIXWYuIbXgLvSwXqZaaLQxebIQg4YAxeY37LXgLQ40= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a17:90a:d817:b0:2d3:cfe1:3205 with SMTP id 98e67ed59e1d1-2d3e041dd44mr104680a91.7.1724077147516; Mon, 19 Aug 2024 07:19:07 -0700 (PDT) Date: Mon, 19 Aug 2024 07:19:07 -0700 In-Reply-To: <20240819121926.GG2032816@nvidia.com> Mime-Version: 1.0 References: <20240809160909.1023470-1-peterx@redhat.com> <20240809160909.1023470-7-peterx@redhat.com> <20240814130525.GH2032816@nvidia.com> <81080764-7c94-463f-80d3-e3b2968ddf5f@redhat.com> <20240819121926.GG2032816@nvidia.com> Message-ID: Subject: Re: [PATCH 06/19] mm/pagewalk: Check pfnmap early for folio_walk_start() From: Sean Christopherson To: Jason Gunthorpe Cc: David Hildenbrand , Peter Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oscar Salvador , Axel Rasmussen , linux-arm-kernel@lists.infradead.org, x86@kernel.org, Will Deacon , Gavin Shan , Paolo Bonzini , Zi Yan , Andrew Morton , Catalin Marinas , Ingo Molnar , Alistair Popple , Borislav Petkov , Thomas Gleixner , kvm@vger.kernel.org, Dave Hansen , Alex Williamson , Yan Zhao Content-Type: text/plain; charset="us-ascii" X-Rspam-User: X-Stat-Signature: fts6c7e4yn7yg5gaobqu6nrc431omo5g X-Rspamd-Queue-Id: 208AA1C002F X-Rspamd-Server: rspam11 X-HE-Tag: 1724077148-129624 X-HE-Meta: U2FsdGVkX1/0YEi9obAonr15ozB4ZV6r6HSpTTyMG1IwF9KC31uSpNukNe46b2e/Xp9G+JSoVhT3+2kiTzLiVDWFnoBO4EwRzP8hxrO7yXyIj1qen4wlMsjmSF3H8rOpItjTDton3y6xGvf4DQ25l1Zk0OKA2hXdljpUUTmOt79EgDkCWkk1KipLqj3ndo00Go/9I3jTVr3XdHa3yjQYZeAozGMAiYreDSa2EjER9CG/0jLZnlGNW8/bJeSYJaxDLvhr0W7hoxKW7CvFhxTkgPO1TfgAXzn1z9EkvkwWoG9GwiuiHOHwYTEQiyQnexfcHtxQyOplBn3pN95kOsFOT49NAKN/NBgPLXgaqXrEYt6pv55w2t6TGZN9Z2FSQRhYvVe5l2HZv34fMw/aMdtSq/0slBDz5oMwlUS3uM/obWZNORdGQwmyGqxS+P/qi2eUfc9R+594A/F1D3iAj4w1/wjzQxtujNyNcu8uoMYP81B91QjaHSRonoo2mJkE/ypegRBQW9yi+oAx01aZ9onEYw9g0sv9aBavIJLe2F305vAxwTL4osaZw9KzqHzZ+5n/ck/GUK5rYxrwWVEzjNtWy2PpMIQbPY6riX8vGLpNiGYrWbWhESpp/CAH86K4SmipCQa5MPkqBUHqUuaWsgBX2RNmA6jnTcsqfOag+zHt0dejzKxRKVNUJuEkY2JU3MBljM1VHXw7cYrXgNOUa7ploZomet9IhMaZEqweklX2+yuWwu1Oai5xa3H34ATjyizT16vOwxybUZY7vEmjxfBqG0i+AQM//R0/ZQ094wjY5DhCFXWPU7RpOGYjX9OIZtetQJx91eEzsIDTvnCl5ttO71gTenywOAk7TBIfGxgt4YxR/9b5pk6m5/+ZYFil5jXniUaRGk4A28DEucVMjv059p7/WsoAEU73KFyUH++K0Gvu3ofdALLipHk3NSukdCpuvNbUQ6JHfjUk3GcqLGH UbdIXGU1 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000015, 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 Mon, Aug 19, 2024, Jason Gunthorpe wrote: > On Fri, Aug 16, 2024 at 07:56:30PM +0200, David Hildenbrand wrote: > > > I think KVM does something nasty: if it something with a "struct page", and > > it's not PageReserved, it would take a reference (if I get > > kvm_pfn_to_refcounted_page()) independent if it's a "normal" or "not normal" > > page -- it essentially ignores the vm_normal_page() information in the page > > tables ... > > Oh that's nasty. Nothing should be upgrading the output of the follow > functions to refcounted. That's what GUP is for. > > And PFNMAP pages, even if they have struct pages for some reason, > should *NEVER* be refcounted because they are in a PFNMAP VMA. That is > completely against the whole point :\ If they could be safely > refcounted then it would be a MIXEDMAP. Yeah yeah, I'm working on it. https://lore.kernel.org/all/20240726235234.228822-1-seanjc@google.com