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vfio/pci: Expose setup ROM at ROM bar when needed

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If ROM bar is missing for any reason, we can fallback to using pdev->rom
to expose the ROM content to the guest. This fixes some passthrough use
cases where the upstream bridge does not have enough address window.

Signed-off-by: Yunxiang Li <Yunxiang.Li@amd.com>
Link: https://lore.kernel.org/r/20250102185013.15082-3-Yunxiang.Li@amd.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Yunxiang Li 2025-01-02 13:50:13 -05:00 committed by Alex Williamson
parent c5a8b5d740
commit e021e6cbfb
3 changed files with 38 additions and 22 deletions
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4
drivers/vfio/pci/vfio_pci_config.c
View File

@ -511,6 +511,10 @@ static void vfio_bar_fixup(struct vfio_pci_core_device *vdev)
mask = ~(pci_resource_len(pdev, PCI_ROM_RESOURCE) - 1);
mask |= PCI_ROM_ADDRESS_ENABLE;
*vbar &= cpu_to_le32((u32)mask);
} else if (pdev->rom && pdev->romlen) {
mask = ~(roundup_pow_of_two(pdev->romlen) - 1);
mask |= PCI_ROM_ADDRESS_ENABLE;
*vbar &= cpu_to_le32((u32)mask);
} else {
*vbar = 0;
}

34
drivers/vfio/pci/vfio_pci_core.c
View File

@ -1054,25 +1054,27 @@ static int vfio_pci_ioctl_get_region_info(struct vfio_pci_core_device *vdev,
info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
info.flags = 0;
info.size = 0;
/* Report the BAR size, not the ROM size */
info.size = pci_resource_len(pdev, info.index);
if (!info.size)
break;
/*
* Is it really there? Enable memory decode for implicit access
* in pci_map_rom().
*/
cmd = vfio_pci_memory_lock_and_enable(vdev);
io = pci_map_rom(pdev, &size);
if (io) {
if (pci_resource_start(pdev, PCI_ROM_RESOURCE)) {
/*
* Check ROM content is valid. Need to enable memory
* decode for ROM access in pci_map_rom().
*/
cmd = vfio_pci_memory_lock_and_enable(vdev);
io = pci_map_rom(pdev, &size);
if (io) {
info.flags = VFIO_REGION_INFO_FLAG_READ;
/* Report the BAR size, not the ROM size. */
info.size = pci_resource_len(pdev, PCI_ROM_RESOURCE);
pci_unmap_rom(pdev, io);
}
vfio_pci_memory_unlock_and_restore(vdev, cmd);
} else if (pdev->rom && pdev->romlen) {
info.flags = VFIO_REGION_INFO_FLAG_READ;
pci_unmap_rom(pdev, io);
} else {
info.size = 0;
/* Report BAR size as power of two. */
info.size = roundup_pow_of_two(pdev->romlen);
}
vfio_pci_memory_unlock_and_restore(vdev, cmd);
break;
}

22
drivers/vfio/pci/vfio_pci_rdwr.c
View File

@ -237,6 +237,8 @@ ssize_t vfio_pci_bar_rw(struct vfio_pci_core_device *vdev, char __user *buf,
if (pci_resource_start(pdev, bar))
end = pci_resource_len(pdev, bar);
else if (bar == PCI_ROM_RESOURCE && pdev->rom && pdev->romlen)
end = roundup_pow_of_two(pdev->romlen);
else
return -EINVAL;
@ -251,11 +253,14 @@ ssize_t vfio_pci_bar_rw(struct vfio_pci_core_device *vdev, char __user *buf,
* excluded range at the end of the actual ROM. This makes
* filling large ROM BARs much faster.
*/
io = pci_map_rom(pdev, &x_start);
if (!io) {
done = -ENOMEM;
goto out;
if (pci_resource_start(pdev, bar)) {
io = pci_map_rom(pdev, &x_start);
} else {
io = ioremap(pdev->rom, pdev->romlen);
x_start = pdev->romlen;
}
if (!io)
return -ENOMEM;
x_end = end;
} else {
int ret = vfio_pci_core_setup_barmap(vdev, bar);
@ -278,8 +283,13 @@ ssize_t vfio_pci_bar_rw(struct vfio_pci_core_device *vdev, char __user *buf,
if (done >= 0)
*ppos += done;
if (bar == PCI_ROM_RESOURCE)
pci_unmap_rom(pdev, io);
if (bar == PCI_ROM_RESOURCE) {
if (pci_resource_start(pdev, bar))
pci_unmap_rom(pdev, io);
else
iounmap(io);
}
out:
return done;
}