On Tue, May 13, 2014 at 11:35:24AM +1000, Gavin Shan wrote:
>The MSIx vector table lives in device memory, which may be cleared as
>part of a backdoor device reset. This is the case on the IBM IPR HBA
>when the BIST is run on the device. When assigned to a QEMU guest,
>the guest driver does a pci_save_state(), issues a BIST, then does a
>pci_restore_state(). The BIST clears the MSIx vector table, but due
>to the way interrupts are configured the pci_restore_state() does not
>restore the vector table as expected. Eventually this results in an
>EEH error on Power platforms when the device attempts to signal an
>interrupt with the zero'd table entry.
>
>Fix the problem by restoring the host cached MSI message prior to
>enabling each vector.
>
>Reported-by: Wen Xiong <wenxiong@xxxxxxxxxxxxxxxxxx>
>Signed-off-by: Gavin Shan <gwshan@xxxxxxxxxxxxxxxxxx>
>Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
>---
Sorry about that the following line was missed. I'll add that and send
"v3" out.
#include <linux/msi.h>
> drivers/vfio/pci/vfio_pci_intrs.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
>diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
>index 9dd49c9..409346f 100644
>--- a/drivers/vfio/pci/vfio_pci_intrs.c
>+++ b/drivers/vfio/pci/vfio_pci_intrs.c
>@@ -548,6 +548,20 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_device *vdev,
> return PTR_ERR(trigger);
> }
>
>+ /*
>+ * The MSIx vector table resides in device memory which may be cleared
>+ * via backdoor resets. We don't allow direct access to the vector
>+ * table so even if a userspace driver attempts to save/restore around
>+ * such a reset it would be unsuccessful. To avoid this, restore the
>+ * cached value of the message prior to enabling.
>+ */
>+ if (msix) {
>+ struct msi_msg msg;
>+
>+ get_cached_msi_msg(irq, &msg);
>+ write_msi_msg(irq, &msg);
>+ }
>+
> ret = request_irq(irq, vfio_msihandler, 0,
> vdev->ctx[vector].name, trigger);
> if (ret) {
Thanks,
Gavin
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