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i6aRPBr9g7ej4S9krUjOdNf2krAZkRiSlxoWt9c6dufHMawrowzGCtkbeDIfReDSW6CFLP6+lkkG7ni0TdIOtgLqF9MycHwVlu0PW6TLEW+GIMn4dj4OuUXHl32R3bFyi81a4bBUA4YmGAvaM9Z0SIbRRi//GD3HKkdWrhSyj23fyfaokV68o7I5mmBShHWRfnO7Osb57iZvyqIF+EO75uNIml+SiS0JewfLpaYIOraigmA7cGdIxRUoF7VnanrGa/e+dBa4s6a152bZBaLHhj4XjLgMs9R5RnG2P4Ydlt+8g50yDhN1DA/qTZKBx4pK37GveeYfhczHIWGFSV7POEf/PzZilIqWHpDvBUA6sg18vz2bXuu1broN6/q1pPjuIvz+dwlnd/7lwcOJECcpJtCSSp3WS8Fm4ZKOY 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, Sep 04, 2024 at 09:38:22AM -0700, Jiaqi Yan wrote: > On Wed, Sep 4, 2024 at 8:52 AM Jason Gunthorpe wrote: > > > > On Thu, Aug 29, 2024 at 12:21:39PM -0700, Jiaqi Yan wrote: > > > > > I think we still want to attempt to SIGBUS userspace, regardless of > > > doing unmap_mapping_range or not. > > > > IMHO we need to eliminate this path if we actually want to keep things > > mapped. > > > > There is no way to generate the SIGBUS without poking a 4k hole in the > > 1G page, as only that 4k should get SIGBUS, every other byte of the 1G > > is clean. > > Ah, sorry I wasn't clear. The SIGBUS will be only for poisoned PFN; > clean PFNs under the same PUD/PMD for sure don't need any SIGBUS, > which is the whole purpose of not unmapping. You can't get a SIGBUS if the things are still mapped. This is why the SIGBUS flow requires poking a non-present hole around the poisoned memory. So keeping things mapped at 1G also means giving up on SIGBUS. Jason