From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexey Kardashevskiy Subject: [RFC PATCH kernel] vfio-pci: Fix sparse capability when no parts of MSIX BAR can be mapped Date: Thu, 23 Nov 2017 15:56:26 +1100 Message-ID: <20171123045626.17542-1-aik@ozlabs.ru> Cc: Alexey Kardashevskiy , Alex Williamson To: kvm@vger.kernel.org Return-path: Received: from ozlabs.ru ([107.173.13.209]:53426 "EHLO ozlabs.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752233AbdKWE4d (ORCPT ); Wed, 22 Nov 2017 23:56:33 -0500 Sender: kvm-owner@vger.kernel.org List-ID: It is currently possible to have a sparse capability with 1 areas which starts at 0 and 0 bytes long. One example is: Texas Instruments TUSB73x0 SuperSpeed USB 3.0 xHCI Host Controller [...] Region 0: Memory at 3fe280000000 (64-bit, non-prefetchable) [size=64K] Region 2: Memory at 3fe280010000 (64-bit, non-prefetchable) [size=8K] [...] Capabilities: [c0] MSI-X: Enable+ Count=8 Masked- Vector table: BAR=2 offset=00000000 PBA: BAR=2 offset=00001000 With PAGE_SIZE=64K, MSIX BAR occupies the entire BAR2 and cannot be mapped. This makes it explicit - if sparse->areas is empty, then advertise nr_areas as 0. Signed-off-by: Alexey Kardashevskiy --- QEMU gets it right as vfio_setup_region_sparse_mmaps() checks for size after QEMU's 24acf72b9a291ce "vfio: Handle zero-length sparse mmap ranges" but why not make it explicit in the first place? --- drivers/vfio/pci/vfio_pci.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c index f041b1a..a201c45 100644 --- a/drivers/vfio/pci/vfio_pci.c +++ b/drivers/vfio/pci/vfio_pci.c @@ -597,6 +597,10 @@ static int msix_sparse_mmap_cap(struct vfio_pci_device *vdev, i++; } + /* With all alignments, there are no gaps left to mmap */ + if (i == 0) + sparse->nr_areas = 0; + ret = vfio_info_add_capability(caps, VFIO_REGION_INFO_CAP_SPARSE_MMAP, sparse); kfree(sparse); -- 2.11.0