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U2FsdGVkX18GtG+FwVr2ZstCSAhxetMnJiHcMPEZXaU9oAQsW0txi4rPr5iyxdSq4vv4115/vIcc8EU23EnHGj5+R2V/jmRgTa1HXoOc2HTfl72sr9uHtgGg0P7JcPoDhZwSdUZZVajz2bsQjn/X00ANj/BgVTwQlwpX6pdmSkVAZZDcEk882aFZEl/b8qh/nqq+woFTrLKtIHd2G0WCkZn5MkPIleit+gX+K80EHfLaVyDwCqtPWxGa1fWwItsUBgdMsndbfUNO9mqac8kiuR0ugzc9LCub0x8BpgGNrFaIsPznN4aRZ8QY/EhhxDV/Rp85q8ncRKkTASx7yZoaJ9aXIsnA/k5XrSJgyF8HH+CfxtEUtvYbX5KWaR3k4rWGX59Gypf5v0gVXJfbDqTS0nCNxZnW3Al4K16TE5CAuo3CoXkhmH8Rmxxsl6WG4Wowv+ykiOtU04ixhb0XPXc2OfMaREQYtUd1AVR957strvm1EinARdkuPVmyQyd+nRdCUo3mDlAej//nv7Y+bXjj4oBBLeGuIa30ttlhq+sN4pKyoiVCYzUy2Xnbo5iE5H6CpdbzmYfgYIFB2dVaxi+634HwxnXJchhl8JfV0ACKLsyIsOCyihWrSPKtxbvPjy/89UI9z+O3eFO5KwFXJNY7v+/5S1DREazf3onBocJpNNn8eT/lu5hx7fXGFN9D1o8tWS7g0msxDbDbFQJ2+glWFpxbJ+W6CO6pbpUyYCS+N+DFdoR/LorhMYymYik7ePkeAy7K3Phe4Qm9cw1jr9PfGwcIC88l2jj5KP8XPVsGD9DbEVUlPJg+3YX86UuootQgmt8SvKwhTFSuHtGC1Ek4jZfRRcamkaqw+8gTE7rj/5zKndqxhAqJPbKVMEDQ0iXKKjPR7kpo/m5vTBbf72+nG+Ys9XaN3+h/Gb10Z+Rxku1FVgi8+KNbMz1QSl6fS6QXE1S4gl77no9i9KaW+tu cVEGK1rF 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 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 10/2/24 4:11 PM, Dave Hansen wrote: > About TLB flushing... > > The quick and dirty thing to do is just flush_tlb_all() after you remove > the PTE from the host mm. That will surely work everywhere and it's as > dirt simple as you get. Honestly, it might even be cheaper than the > alternative. I think this a good place to start from. My concern is that unnecessary flushes will potentially impact unrelated loads. Performance testing as things progress can help determine if a more involved approach is needed. > > Also, I don't think PCIDs actually complicate the problem at all. We > basically do remote mm TLB flushes using two mechanisms: > > 1. If the mm is loaded, use INVLPG and friends to zap the TLB > 2. Bump mm->context.tlb_gen so that the next time it _gets_ > loaded, the TLB is flushed. > > flush_tlb_func() really only cares about #1 since if the mm isn't > loaded, it'll get flushed anyway at the next context switch. > > The alternatives I can think of: > > Make flush_tlb_mm_range(host_mm) work somehow. You'd need to somehow > keep mm_cpumask(host_mm) up to date and also make do something to > flush_tlb_func() to tell it that 'loaded_mm' isn't relevant and it > should flush regardless. > > The other way is to use the msharefs's inode ->i_mmap to find all the > VMAs mapping the file, and find all *their* mm's: > > for each vma in inode->i_mmap > mm = vma->vm_mm > flush_tlb_mm_range() > > But that might be even worse than flush_tlb_all() because it might end > up sending more than one IPI per CPU. > > You can fix _that_ by keeping a single cpumask that you build up: > > mask = 0 > for each vma in inode->i_mmap > mm = vma->vm_mm > mask |= mm_cpumask(mm) > > flush_tlb_multi(mask, info); > > Unfortunately, 'info->mm' needs to be more than one mm, so you probably > still need a new flush_tlb_func() flush type to tell it to ignore > 'info->mm' and flush anyway. What about something like arch_tlbbatch_flush() which sets info->mm to NULL and uses a batch cpumask? That seems perfect though there would be a bit more work needed to ensure things work on other architectures. flush_tlb_all() it is then, for now. :-) > > After all that, I kinda like flush_tlb_all(). ;)