Re: [PATCH 4/4] vfio/pci: Restore MSIx message prior to enabling

[Alex Williamson <alex.williamson@redhat.com>]

On Fri, 2014-09-26 at 13:19 +1000, Gavin Shan wrote:
> On Wed, Sep 10, 2014 at 06:13:42PM +1000, Gavin Shan wrote:
> >On Mon, May 19, 2014 at 01:01:10PM +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@linux.vnet.ibm.com>
> >>Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
> >>Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> >
> >Alex, please let me know if I need resend this one to you. The patch
> >has been pending for long time, I'm not sure if you still can grab
> >it somewhere.
> >
> >As you might see, Bjorn will take that one with PCI changes. This patch
> >depends on the changes.
> >
> 
> Alex, I guess you probably missed last reply. Bjorn acked the first
> patch and you can pick both of them if I understand correctly. Please
> let me know if I need resend those 2 patches?

Please update the patches, add Bjorn's ACK, test and resend.  I'd like
to at least know that it still applies and resolves the problem on the
current code base since the patch is 4 months old.  Thanks,

Alex

> >>---
> >> drivers/vfio/pci/vfio_pci_intrs.c | 15 +++++++++++++++
> >> 1 file changed, 15 insertions(+)
> >>
> >>diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> >>index 9dd49c9..553212f 100644
> >>--- a/drivers/vfio/pci/vfio_pci_intrs.c
> >>+++ b/drivers/vfio/pci/vfio_pci_intrs.c
> >>@@ -16,6 +16,7 @@
> >> #include <linux/device.h>
> >> #include <linux/interrupt.h>
> >> #include <linux/eventfd.h>
> >>+#include <linux/msi.h>
> >> #include <linux/pci.h>
> >> #include <linux/file.h>
> >> #include <linux/poll.h>
> >>@@ -548,6 +549,20 @@ 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) {
> >>-- 
> >>1.8.3.2
> >>
>