[PULL 3/7] vfio: Do not reattempt a failed rom read

Alex Williamson
2014-01-17T19:25:30Z

From: Bandan Das <bsd@redhat.com>

During lazy rom loading, if rom read fails, and the
guest attempts a read again, vfio will again attempt it.
Add a boolean to prevent this. There could be a case where
a failed rom read might succeed the next time because of
a device reset or such, but it's best to exclude unpredictable
behavior

Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
hw/misc/vfio.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
index ef615fc..30b1a78 100644
--- a/hw/misc/vfio.c
+++ b/hw/misc/vfio.c
@@ -191,6 +191,7 @@ typedef struct VFIODevice {
bool has_flr;
bool has_pm_reset;
bool needs_reset;
+ bool rom_read_failed;
} VFIODevice;

typedef struct VFIOGroup {
@@ -1125,6 +1126,7 @@ static void vfio_pci_load_rom(VFIODevice *vdev)
vdev->rom_offset = reg_info.offset;

if (!vdev->rom_size) {
+ vdev->rom_read_failed = true;
error_report("vfio-pci: Cannot read device rom at "
"%04x:%02x:%02x.%x\n",
vdev->host.domain, vdev->host.bus, vdev->host.slot,
@@ -1163,6 +1165,9 @@ static uint64_t vfio_rom_read(void *opaque, hwaddr addr, unsigned size)
/* Load the ROM lazily when the guest tries to read it */
if (unlikely(!vdev->rom)) {
vfio_pci_load_rom(vdev);
+ if (unlikely(!vdev->rom && !vdev->rom_read_failed)) {
+ vfio_pci_load_rom(vdev);
+ }
}

memcpy(&val, vdev->rom + addr,
@@ -1230,6 +1235,7 @@ static void vfio_pci_size_rom(VFIODevice *vdev)
PCI_BASE_ADDRESS_SPACE_MEMORY, &vdev->pdev.rom);

vdev->pdev.has_rom = true;
+ vdev->rom_read_failed = false;
}

static void vfio_vga_write(void *opaque, hwaddr addr,