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charset="us-ascii" X-Stat-Signature: q3qo719gm97d58qndrhuy1xd5rr4atrd X-Rspamd-Queue-Id: 18EF0A001C X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1723646103-776269 X-HE-Meta: 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 QIEGTzv0 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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 Wed, Aug 14, 2024, Jason Gunthorpe wrote: > On Fri, Aug 09, 2024 at 12:08:50PM -0400, Peter Xu wrote: > > Overview > > ======== > > > > This series is based on mm-unstable, commit 98808d08fc0f of Aug 7th latest, > > plus dax 1g fix [1]. Note that this series should also apply if without > > the dax 1g fix series, but when without it, mprotect() will trigger similar > > errors otherwise on PUD mappings. > > > > This series implements huge pfnmaps support for mm in general. Huge pfnmap > > allows e.g. VM_PFNMAP vmas to map in either PMD or PUD levels, similar to > > what we do with dax / thp / hugetlb so far to benefit from TLB hits. Now > > we extend that idea to PFN mappings, e.g. PCI MMIO bars where it can grow > > as large as 8GB or even bigger. > > FWIW, I've started to hear people talk about needing this in the VFIO > context with VMs. > > vfio/iommufd will reassemble the contiguous range from the 4k PFNs to > setup the IOMMU, but KVM is not able to do it so reliably. Heh, KVM should very reliably do the exact opposite, i.e. KVM should never create a huge page unless the mapping is huge in the primary MMU. And that's very much by design, as KVM has no knowledge of what actually resides at a given PFN, and thus can't determine whether or not its safe to create a huge page if KVM happens to realize the VM has access to a contiguous range of memory.