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x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 23 Aug 2023 12:16:23 -0300 Jason Gunthorpe wrote: > On Wed, Aug 23, 2023 at 09:14:07AM -0600, Alex Williamson wrote: > > On Wed, 23 Aug 2023 14:50:31 +0000 > > Ankit Agrawal wrote: > > > > > >> + if (index == VFIO_PCI_BAR2_REGION_INDEX) { > > > >> + if (!nvdev->opregion) { > > > >> + nvdev->opregion = memremap(nvdev->hpa, nvdev->mem_length, MEMREMAP_WB); > > > >> + if (!nvdev->opregion) > > > >> + return -ENOMEM; > > > >> + } > > > > > > > > [AW] Seems like this would be susceptible to concurrent accesses causing > > > > duplicate mappings. > > > > > > > > [JG] Needs some kind of locking on opregion > > > > > > Right, will add a new lock item in nvdev to control the access to opregion/memmap. > > > Please let me know if it is preferable to do memremap in open_device instead of > > > read/write. > > > > That's a valid option also, certainly avoids the locking and > > serialization per access. Thanks, > > open_device is no good, that would waste large amounts of kernel > memory for page tables to support something we don't expect to be > used. A lock it is then, I guess this is a very large range of memory. The contention/serialization is also not a priority, we expect access through the mmap for anything other than debug. Thanks, Alex