[PATCH 2/4] xen/pciback: Save the number of MSI-X entries to be copied later.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

c/s  8135cf8b092723dbfcc611fe6fdcb3a36c9951c5
"xen/pciback: Save xen_pci_op commands before processing it"
would copyback the processed values - which was great.

However it missed the case that xen_pcibk_enable_msix - when
completing would overwrite op->value (which had the number
of MSI-X vectors requested) with the return value (which for
success was zero). Hence the copy-back routine (which would use
op->value) would copy exactly zero MSI-X vectors back.

CC: stable@vger.kernel.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 drivers/xen/xen-pciback/pciback_ops.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/xen/xen-pciback/pciback_ops.c b/drivers/xen/xen-pciback/pciback_ops.c
index 8c86a53..2fc5880 100644
--- a/drivers/xen/xen-pciback/pciback_ops.c
+++ b/drivers/xen/xen-pciback/pciback_ops.c
@@ -335,7 +335,9 @@ void xen_pcibk_do_op(struct work_struct *data)
 	struct xen_pcibk_dev_data *dev_data = NULL;
 	struct xen_pci_op *op = &pdev->op;
 	int test_intx = 0;
-
+#ifdef CONFIG_PCI_MSI
+	unsigned int nr = 0;
+#endif
 	*op = pdev->sh_info->op;
 	barrier();
 	dev = xen_pcibk_get_pci_dev(pdev, op->domain, op->bus, op->devfn);
@@ -363,6 +365,7 @@ void xen_pcibk_do_op(struct work_struct *data)
 			op->err = xen_pcibk_disable_msi(pdev, dev, op);
 			break;
 		case XEN_PCI_OP_enable_msix:
+			nr = op->value;
 			op->err = xen_pcibk_enable_msix(pdev, dev, op);
 			break;
 		case XEN_PCI_OP_disable_msix:
@@ -385,7 +388,7 @@ void xen_pcibk_do_op(struct work_struct *data)
 	if (op->cmd == XEN_PCI_OP_enable_msix && op->err == 0) {
 		unsigned int i;
 
-		for (i = 0; i < op->value; i++)
+		for (i = 0; i < nr; i++)
 			pdev->sh_info->op.msix_entries[i].vector =
 				op->msix_entries[i].vector;
 	}
-- 
2.1.0