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From 9291ea1d33e70d9c01558da25ac6744ff2ef77ec Mon Sep 17 00:00:00 2001
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From: Alex Williamson <alex.williamson@redhat.com>
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Date: Fri, 29 Sep 2017 21:46:24 +0200
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Subject: [PATCH 16/27] vfio: Handle zero-length sparse mmap ranges
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RH-Author: Alex Williamson <alex.williamson@redhat.com>
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Message-id: <20170929214624.16765.84023.stgit@gimli.home>
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Patchwork-id: 76774
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O-Subject: [RHEL-7.5 qemu-kvm PATCH 16/16] vfio: Handle zero-length sparse mmap ranges
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Bugzilla: 1494181
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Auger Eric <eric.auger@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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Upstream: 24acf72b9a291cebfd05f2ecdf3a982ac01e6291
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As reported in the link below, user has a PCI device with a 4KB BAR
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which contains the MSI-X table. This seems to hit a corner case in
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the kernel where the region reports being mmap capable, but the sparse
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mmap information reports a zero sized range. It's not entirely clear
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that the kernel is incorrect in doing this, but regardless, we need
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to handle it. To do this, fill our mmap array only with non-zero
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sized sparse mmap entries and add an error return from the function
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so we can tell the difference between nr_mmaps being zero based on
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sparse mmap info vs lack of sparse mmap info.
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NB, this doesn't actually change the behavior of the device, it only
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removes the scary "Failed to mmap ... Performance may be slow" error
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message. We cannot currently create an mmap over the MSI-X table.
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Link: http://lists.nongnu.org/archive/html/qemu-discuss/2016-10/msg00009.html
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Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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hw/misc/vfio.c | 36 ++++++++++++++++++++++--------------
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1 file changed, 22 insertions(+), 14 deletions(-)
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diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
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index a27698b..68ff949 100644
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--- a/hw/misc/vfio.c
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+++ b/hw/misc/vfio.c
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@@ -2621,16 +2621,16 @@ vfio_get_region_info_cap(struct vfio_region_info *info, uint16_t id)
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return NULL;
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}
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-static void vfio_setup_region_sparse_mmaps(VFIORegion *region,
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- struct vfio_region_info *info)
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+static int vfio_setup_region_sparse_mmaps(VFIORegion *region,
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+ struct vfio_region_info *info)
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{
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struct vfio_info_cap_header *hdr;
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struct vfio_region_info_cap_sparse_mmap *sparse;
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- int i;
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+ int i, j;
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hdr = vfio_get_region_info_cap(info, VFIO_REGION_INFO_CAP_SPARSE_MMAP);
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if (!hdr) {
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- return;
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+ return -ENODEV;
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}
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sparse = container_of(hdr, struct vfio_region_info_cap_sparse_mmap, header);
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@@ -2638,16 +2638,24 @@ static void vfio_setup_region_sparse_mmaps(VFIORegion *region,
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trace_vfio_region_sparse_mmap_header(region->vbasedev->name,
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region->nr, sparse->nr_areas);
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- region->nr_mmaps = sparse->nr_areas;
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- region->mmaps = g_new0(VFIOMmap, region->nr_mmaps);
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+ region->mmaps = g_new0(VFIOMmap, sparse->nr_areas);
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- for (i = 0; i < region->nr_mmaps; i++) {
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- region->mmaps[i].offset = sparse->areas[i].offset;
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- region->mmaps[i].size = sparse->areas[i].size;
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- trace_vfio_region_sparse_mmap_entry(i, region->mmaps[i].offset,
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- region->mmaps[i].offset +
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- region->mmaps[i].size);
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+ for (i = 0, j = 0; i < sparse->nr_areas; i++) {
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+ trace_vfio_region_sparse_mmap_entry(i, sparse->areas[i].offset,
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+ sparse->areas[i].offset +
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+ sparse->areas[i].size);
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+
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+ if (sparse->areas[i].size) {
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+ region->mmaps[j].offset = sparse->areas[i].offset;
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+ region->mmaps[j].size = sparse->areas[i].size;
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+ j++;
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+ }
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}
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+
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+ region->nr_mmaps = j;
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+ region->mmaps = g_realloc(region->mmaps, j * sizeof(VFIOMmap));
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+
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+ return 0;
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}
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static int vfio_region_setup(Object *obj, VFIODevice *vbasedev,
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@@ -2676,9 +2684,9 @@ static int vfio_region_setup(Object *obj, VFIODevice *vbasedev,
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region->flags & VFIO_REGION_INFO_FLAG_MMAP &&
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!(region->size & ~TARGET_PAGE_MASK)) {
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- vfio_setup_region_sparse_mmaps(region, info);
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+ ret = vfio_setup_region_sparse_mmaps(region, info);
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- if (!region->nr_mmaps) {
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+ if (ret) {
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region->nr_mmaps = 1;
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region->mmaps = g_new0(VFIOMmap, region->nr_mmaps);
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region->mmaps[0].offset = 0;
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--
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1.8.3.1
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