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Subject[PATCH v3] vfio_pci: Enable memory accesses before calling pci_map_rom
Date
pci_map_rom/pci_get_rom_size() performs memory access in the ROM.
In case the Memory Space accesses were disabled, readw() is likely
to trigger a synchronous external abort on some platforms.

In case memory accesses were disabled, re-enable them before the
call and disable them back again just after.

Fixes: 89e1f7d4c66d ("vfio: Add PCI device driver")

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Suggested-by: Alex Williamson <alex.williamson@redhat.com>

---
v2 -> v3:
- follow Alex re-writing

v1 -> v2:
- also re-enable in case of error
---
drivers/vfio/pci/vfio_pci.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index ff60bd1ea587..4b0d30f1eabc 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -708,6 +708,7 @@ static long vfio_pci_ioctl(void *device_data,
{
void __iomem *io;
size_t size;
+ u16 orig_cmd;

info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
info.flags = 0;
@@ -723,15 +724,23 @@ static long vfio_pci_ioctl(void *device_data,
break;
}

- /* Is it really there? */
- io = pci_map_rom(pdev, &size);
- if (!io || !size) {
- info.size = 0;
- break;
- }
- pci_unmap_rom(pdev, io);
+ /*
+ * Is it really there? Enable memory decode for
+ * implicit access in pci_map_rom().
+ */
+ pci_read_config_word(pdev, PCI_COMMAND, &orig_cmd);
+ pci_write_config_word(pdev, PCI_COMMAND,
+ orig_cmd | PCI_COMMAND_MEMORY);

- info.flags = VFIO_REGION_INFO_FLAG_READ;
+ io = pci_map_rom(pdev, &size);
+ if (io) {
+ info.flags = VFIO_REGION_INFO_FLAG_READ;
+ pci_unmap_rom(pdev, io);
+ } else {
+ info.size = 0;
+ }
+
+ pci_write_config_word(pdev, PCI_COMMAND, orig_cmd);
break;
}
case VFIO_PCI_VGA_REGION_INDEX:
--
2.20.1
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