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[47.55.120.4]) by smtp.gmail.com with ESMTPSA id af79cd13be357-89f2421fc6fsm597656885a.9.2025.10.27.06.39.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Oct 2025 06:39:05 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1vDNRA-00000004F6U-3Inv; Mon, 27 Oct 2025 10:39:04 -0300 Date: Mon, 27 Oct 2025 10:39:04 -0300 From: Jason Gunthorpe To: Alex Mastro Cc: Alex Williamson , Alejandro Jimenez , David Matlack , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 0/3] vfio: handle DMA map/unmap up to the addressable limit Message-ID: <20251027133904.GE760669@ziepe.ca> References: <20251012-fix-unmap-v4-0-9eefc90ed14c@fb.com> Precedence: bulk X-Mailing-List: linux-kernel@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 Sat, Oct 25, 2025 at 11:11:49AM -0700, Alex Mastro wrote: > Alex and Jason, during my testing, I found that the behavior of range-based > (!VFIO_DMA_UNMAP_FLAG_ALL) VFIO_IOMMU_UNMAP_DMA differs slightly when using > /dev/iommu as the container. > > iommufd treats range-based unmap where there are no hits in the range as an > error, and the ioctl fails with ENOENT. > vfio_iommu_type1.c treats this as a success and reports zero bytes unmapped in > vfio_iommu_type1_dma_unmap.size. Oh, weird... What do you think about this: diff --git a/drivers/iommu/iommufd/io_pagetable.c b/drivers/iommu/iommufd/io_pagetable.c index c0360c450880b8..1124f68ec9020d 100644 --- a/drivers/iommu/iommufd/io_pagetable.c +++ b/drivers/iommu/iommufd/io_pagetable.c @@ -707,7 +707,8 @@ static int iopt_unmap_iova_range(struct io_pagetable *iopt, unsigned long start, struct iopt_area *area; unsigned long unmapped_bytes = 0; unsigned int tries = 0; - int rc = -ENOENT; + /* If there are no mapped entries then success */ + int rc = 0; /* * The domains_rwsem must be held in read mode any time any area->pages diff --git a/drivers/iommu/iommufd/ioas.c b/drivers/iommu/iommufd/ioas.c index 1542c5fd10a85c..ef5e56672dea56 100644 --- a/drivers/iommu/iommufd/ioas.c +++ b/drivers/iommu/iommufd/ioas.c @@ -367,6 +367,8 @@ int iommufd_ioas_unmap(struct iommufd_ucmd *ucmd) &unmapped); if (rc) goto out_put; + if (!unmapped) + rc = -ENOENT; } cmd->length = unmapped; Thanks, Jason