Hello Farhan,
On 12/19/25 18:30, Farhan Ali wrote:
On 12/19/2025 8:30 AM, Cédric Le Goater wrote:
On 12/19/25 17:21, Philippe Mathieu-Daudé wrote:
On 19/12/25 15:51, Cédric Le Goater wrote:
Hello,
On 12/17/25 19:42, Farhan Ali wrote:
The VFIO pread/pwrite functions use little-endian data format.
When enabling the Bus Master bit, the value must be correctly converted
from the CPU's native endianess to little-endian format.
How did you find the issue ?
I presumed using VFIO on s390x hosts...
yes. I have been using a nvme drive for over 2y in an s390x VM and never
saw any issue.
C.
Hi Cedric,
I have recently been experimenting with QEMU NVMe userspace driver and PCI
instructions from userspace [1]. On some of our test systems I noticed the
driver being hung. After some investigation we realized it was due to this
issue.
Do you think you could provide a test case for it ?
Also, I think the LE conversion should be done in routines
qemu_vfio_pci_read_config() and qemu_vfio_pci_write_config().
Thanks,
C.
[1] https://lore.kernel.org/all/[email protected]/
Thanks
Farhan
Thanks,
C.
Signed-off-by: Farhan Ali <[email protected]>
---
util/vfio-helpers.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
index fdff042ab4..3c8284284f 100644
--- a/util/vfio-helpers.c
+++ b/util/vfio-helpers.c
@@ -443,7 +443,7 @@ static int qemu_vfio_init_pci(QEMUVFIOState *s, const char
*device,
if (ret) {
goto fail;
}
- pci_cmd |= PCI_COMMAND_MASTER;
+ pci_cmd = cpu_to_le16(le16_to_cpu(pci_cmd) | PCI_COMMAND_MASTER);
ret = qemu_vfio_pci_write_config(s, &pci_cmd, sizeof(pci_cmd),
PCI_COMMAND);
if (ret) {
goto fail;
