vfio_pci: Enable memory accesses before calling pci_map_rom

[ Upstream commit 0cfd027be1d6def4a462cdc180c055143af24069 ]

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>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 4b62eb3..7a82735 100644 (file)
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -496,6 +496,7 @@ 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;
@@ -505,15 +506,23 @@ static long vfio_pci_ioctl(void *device_data,
                        if (!info.size)
                                break;
 
-                       /* Is it really there? */
+                       /*
+                        * 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);
+
                        io = pci_map_rom(pdev, &size);
-                       if (!io || !size) {
+                       if (io) {
+                               info.flags = VFIO_REGION_INFO_FLAG_READ;
+                               pci_unmap_rom(pdev, io);
+                       } else {
                                info.size = 0;
-                               break;
                        }
-                       pci_unmap_rom(pdev, io);
 
-                       info.flags = VFIO_REGION_INFO_FLAG_READ;
+                       pci_write_config_word(pdev, PCI_COMMAND, orig_cmd);
                        break;
                }
                case VFIO_PCI_VGA_REGION_INDEX: