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[34.142.255.199]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84337bbbfacsm2163232b3a.20.2026.06.11.07.43.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Jun 2026 07:43:44 -0700 (PDT) Date: Thu, 11 Jun 2026 14:43:38 +0000 From: Pranjal Shrivastava To: Jason Gunthorpe Cc: linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Bjorn Helgaas , Logan Gunthorpe , Alex Williamson , Kevin Tian , Ankit Agrawal , Matt Evans , Vivek Kasireddy , Leon Romanovsky , Shivaji Kant , Samiullah Khawaja Subject: Re: [RFC PATCH 0/5] vfio/pci: Support ZONE_DEVICE-backed P2P Registration Message-ID: References: <20260610151853.3608948-1-praan@google.com> <20260610162848.GO2764304@ziepe.ca> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Jun 11, 2026 at 02:40:17PM +0000, Pranjal Shrivastava wrote: > On Wed, Jun 10, 2026 at 01:28:48PM -0300, Jason Gunthorpe wrote: > > On Wed, Jun 10, 2026 at 03:18:48PM +0000, Pranjal Shrivastava wrote: > > [...] > > > An alternative implementation has been explored which integrates with the > > > ongoing VFIO DMABUF-mmap refactor [1]. In that approach, rather than > > > registering a BAR as a system-wide P2P provider, VFIO optionally > > > allocates ZONE_DEVICE pages only for specifically exported DMABUFs via a > > > new VFIO_DMA_BUF_FLAG_ALLOC_STRUCT_PAGES flag. > > > > That's probably more sensible but you can't have a DMABUF mmap > > actually install non-special memory. The native vfio mmap still can, > > but not mmap on the dmabuf fd. That's still workable, just keep in > > mind. > > Ack. I guess, we could have a separate mmap path in case of BARs that are > struct page backed which doesn't go through the dmabuf exporter. > > That said, we don't mind moving away from the old API if VFIO mmap can > support this, we don't mind open-coding with devmem_remap_pages. Minor correction, I meant: devm_memremap_pages Thanks, Praan