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vfio: Improve error reporting when MMIO region mapping fails

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When the IOMMU address space width is smaller than the physical
address width, a MMIO region of a device can fail to map because the
region is outside the supported IOVA ranges of the VM. In this case,
PCI peer-to-peer transactions on BARs are not supported. This can
occur with the 39-bit IOMMU address space width, as can be the case on
some Intel consumer processors, or when using a vIOMMU device with
default settings.

The current error message is unclear, improve it and also change the
error report to a warning because it is a non fatal condition for the
VM. To prevent excessive log messages, restrict these recurring DMA
mapping errors to a single warning at runtime.

Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250206131438.1505542-6-clg@redhat.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>
This commit is contained in:
Cédric Le Goater 2025-02-06 14:14:33 +01:00
parent 80936cf7f3
commit aaec00422b
1 changed files with 16 additions and 1 deletions
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17
hw/vfio/common.c
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@ -555,6 +555,18 @@ static bool vfio_get_section_iova_range(VFIOContainerBase *bcontainer,
return true;
}
static void vfio_device_error_append(VFIODevice *vbasedev, Error **errp)
{
/*
* MMIO region mapping failures are not fatal but in this case PCI
* peer-to-peer transactions are broken.
*/
if (vbasedev && vbasedev->type == VFIO_DEVICE_TYPE_PCI) {
error_append_hint(errp, "%s: PCI peer-to-peer transactions "
"on BARs are not supported.\n", vbasedev->name);
}
}
static void vfio_listener_region_add(MemoryListener *listener,
MemoryRegionSection *section)
{
@ -670,7 +682,10 @@ static void vfio_listener_region_add(MemoryListener *listener,
strerror(-ret));
if (memory_region_is_ram_device(section->mr)) {
/* Allow unexpected mappings not to be fatal for RAM devices */
error_report_err(err);
VFIODevice *vbasedev =
vfio_get_vfio_device(memory_region_owner(section->mr));
vfio_device_error_append(vbasedev, &err);
warn_report_err_once(err);
return;
}
goto fail;