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[47.55.120.4]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8846e445922sm102547566d6.8.2025.11.24.09.16.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Nov 2025 09:16:46 -0800 (PST) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vNaBC-00000001wY9-0IF7; Mon, 24 Nov 2025 13:16:46 -0400 Date: Mon, 24 Nov 2025 13:16:46 -0400 From: Jason Gunthorpe To: Shameer Kolothum Cc: Ankit Agrawal , Yishai Hadas , "kevin.tian@intel.com" , "alex@shazbot.org" , Aniket Agashe , Vikram Sethi , Matt Ochs , "Yunxiang.Li@amd.com" , "yi.l.liu@intel.com" , "zhangdongdong@eswincomputing.com" , Avihai Horon , "bhelgaas@google.com" , "peterx@redhat.com" , "pstanner@redhat.com" , Alistair Popple , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Neo Jia , Kirti Wankhede , "Tarun Gupta (SW-GPU)" , Zhi Wang , Dan Williams , Dheeraj Nigam , Krishnakant Jaju Subject: Re: [PATCH v5 1/7] vfio/nvgrace-gpu: Use faults to map device memory Message-ID: <20251124171646.GU233636@ziepe.ca> References: <20251124115926.119027-1-ankita@nvidia.com> <20251124115926.119027-2-ankita@nvidia.com> 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 Mon, Nov 24, 2025 at 05:09:30PM +0000, Shameer Kolothum wrote: > > +static vm_fault_t nvgrace_gpu_vfio_pci_fault(struct vm_fault *vmf) > > +{ > > + struct vm_area_struct *vma = vmf->vma; > > + struct nvgrace_gpu_pci_core_device *nvdev = vma->vm_private_data; > > + int index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT - > > PAGE_SHIFT); > > + vm_fault_t ret = VM_FAULT_SIGBUS; > > + struct mem_region *memregion; > > + unsigned long pgoff, pfn; > > + > > + memregion = nvgrace_gpu_memregion(index, nvdev); > > + if (!memregion) > > + return ret; > > + > > + pgoff = (vmf->address - vma->vm_start) >> PAGE_SHIFT; > > + pfn = PHYS_PFN(memregion->memphys) + pgoff; > > The core fault code seems to calculate the BAR offset in vma_to_pfn() > which is missing here. > > pgoff = vma->vm_pgoff & > ((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1); Yes, that should be included for this reason: > Is the assumption here is user space will always map at BAR offset 0? It should not be assumed. Jason