lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <4fd5f74f-3739-f469-fd8a-ad0ea22ec966@redhat.com> Date: Tue, 2 May 2023 17:45:40 +0200 From: David Hildenbrand <david@...hat.com> To: Jason Gunthorpe <jgg@...dia.com>, Peter Xu <peterx@...hat.com> Cc: Matthew Rosato <mjrosato@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, Lorenzo Stoakes <lstoakes@...il.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, Jens Axboe <axboe@...nel.dk>, Matthew Wilcox <willy@...radead.org>, Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>, Leon Romanovsky <leon@...nel.org>, Christian Benvenuti <benve@...co.com>, Nelson Escobar <neescoba@...co.com>, Bernard Metzler <bmt@...ich.ibm.com>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, Bjorn Topel <bjorn@...nel.org>, Magnus Karlsson <magnus.karlsson@...el.com>, Maciej Fijalkowski <maciej.fijalkowski@...el.com>, Jonathan Lemon <jonathan.lemon@...il.com>, "David S . Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Christian Brauner <brauner@...nel.org>, Richard Cochran <richardcochran@...il.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, linux-fsdevel@...r.kernel.org, linux-perf-users@...r.kernel.org, netdev@...r.kernel.org, bpf@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>, John Hubbard <jhubbard@...dia.com>, Jan Kara <jack@...e.cz>, "Kirill A . Shutemov" <kirill@...temov.name>, Pavel Begunkov <asml.silence@...il.com>, Mika Penttila <mpenttil@...hat.com>, Dave Chinner <david@...morbit.com>, Theodore Ts'o <tytso@....edu> Subject: Re: [PATCH v6 3/3] mm/gup: disallow FOLL_LONGTERM GUP-fast writing to file-backed mappings On 02.05.23 17:36, Jason Gunthorpe wrote: > On Tue, May 02, 2023 at 11:32:57AM -0400, Peter Xu wrote: >>> How does s390 avoid mmu notifiers without having lots of problems?? It >>> is not really optional to hook the invalidations if you need to build >>> a shadow page table.. >> >> Totally no idea on s390 details, but.. per my read above, if the firmware >> needs to make sure the page is always available (so no way to fault it in >> on demand), which means a longterm pinning seems appropriate here. >> >> Then if pinned a must, there's no need for mmu notifiers (as the page will >> simply not be invalidated anyway)? > > And what if someone deliberately changes the mapping? memory hotplug > in the VM, or whatever? Besides s390 not supporting memory hotplug in VMs (yet): if the guest wants a different guest physical address, I guess that's the problem of the guest, and it can update it: KVM_S390_ZPCIOP_REG_AEN is triggered from QEMU via s390_pci_kvm_aif_enable(), triggered by the guest via a special instruction. If the hypervisor changes the mapping, it's just the same thing as mixing e.g. MADV_DONTNEED with longterm pinning in vfio: don't do it. And if you do it, you get to keep the mess you created for your VM. Linux will make sure to not change the mapping: for example, page migration of a pinned page will fail. But maybe I am missing something important here. -- Thanks, David / dhildenb
Powered by blists - more mailing lists