xen: fix MSI setup and teardown for PV on HVM guests

When remapping MSIs into pirqs for PV on HVM guests, qemu is responsible for doing the actual mapping and unmapping. We only give qemu the desired pirq number when we ask to do the mapping the first time, after that we should be reading back the pirq number from qemu every time we want to re-enable the MSI. This fixes a bug in xen_hvm_setup_msi_irqs that manifests itself when trying to enable the same MSI for the second time: the old MSI to pirq mapping is still valid at this point but xen_hvm_setup_msi_irqs would try to assign a new pirq anyway. A simple way to reproduce this bug is to assign an MSI capable network card to a PV on HVM guest, if the user brings down the corresponding ethernet interface and up again, Linux would fail to enable MSIs on the device. Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

xen: fix MSI setup and teardown for PV on HVM guests
When remapping MSIs into pirqs for PV on HVM guests, qemu is responsible for doing the actual mapping and unmapping. We only give qemu the desired pirq number when we ask to do the mapping the first time, after that we should be reading back the pirq number from qemu every time we want to re-enable the MSI. This fixes a bug in xen_hvm_setup_msi_irqs that manifests itself when trying to enable the same MSI for the second time: the old MSI to pirq mapping is still valid at this point but xen_hvm_setup_msi_irqs would try to assign a new pirq anyway. A simple way to reproduce this bug is to assign an MSI capable network card to a PV on HVM guest, if the user brings down the corresponding ethernet interface and up again, Linux would fail to enable MSIs on the device. Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Stefano Stabellini
1 parent e5fc734541
Showing 3 changed files with 43 additions and 15 deletions Side-by-side Diff
arch/x86/pci/xen.c
drivers/xen/events.c
include/xen/events.h
@@ -70,6 +70,9 @@
 struct xen_pci_frontend_ops *xen_pci_frontend;
 EXPORT_SYMBOL_GPL(xen_pci_frontend);
  
+#define XEN_PIRQ_MSI_DATA  (MSI_DATA_TRIGGER_EDGE | \
+		MSI_DATA_LEVEL_ASSERT | (3 << 8) | MSI_DATA_VECTOR(0))
+
 static void xen_msi_compose_msg(struct pci_dev *pdev, unsigned int pirq,
 		struct msi_msg *msg)
 {
@@ -83,12 +86,7 @@
 		MSI_ADDR_REDIRECTION_CPU |
 		MSI_ADDR_DEST_ID(pirq);
  
-	msg->data =
-		MSI_DATA_TRIGGER_EDGE |
-		MSI_DATA_LEVEL_ASSERT |
-		/* delivery mode reserved */
-		(3 << 8) |
-		MSI_DATA_VECTOR(0);
+	msg->data = XEN_PIRQ_MSI_DATA;
 }
  
 static int xen_hvm_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
  
@@ -98,8 +96,23 @@
 	struct msi_msg msg;
  
 	list_for_each_entry(msidesc, &dev->msi_list, list) {
+		__read_msi_msg(msidesc, &msg);
+		pirq = MSI_ADDR_EXT_DEST_ID(msg.address_hi) |
+			((msg.address_lo >> MSI_ADDR_DEST_ID_SHIFT) & 0xff);
+		if (xen_irq_from_pirq(pirq) >= 0 && msg.data == XEN_PIRQ_MSI_DATA) {
+			xen_allocate_pirq_msi((type == PCI_CAP_ID_MSIX) ?
+					"msi-x" : "msi", &irq, &pirq, XEN_ALLOC_IRQ);
+			if (irq < 0)
+				goto error;
+			ret = set_irq_msi(irq, msidesc);
+			if (ret < 0)
+				goto error_while;
+			printk(KERN_DEBUG "xen: msi already setup: msi --> irq=%d"
+					" pirq=%d\n", irq, pirq);
+			return 0;
+		}
 		xen_allocate_pirq_msi((type == PCI_CAP_ID_MSIX) ?
-				"msi-x" : "msi", &irq, &pirq);
+				"msi-x" : "msi", &irq, &pirq, (XEN_ALLOC_IRQ | XEN_ALLOC_PIRQ));
 		if (irq < 0 || pirq < 0)
 			goto error;
 		printk(KERN_DEBUG "xen: msi --> irq=%d, pirq=%d\n", irq, pirq);
@@ -668,17 +668,21 @@
 #include <linux/msi.h>
 #include "../pci/msi.h"
  
-void xen_allocate_pirq_msi(char *name, int *irq, int *pirq)
+void xen_allocate_pirq_msi(char *name, int *irq, int *pirq, int alloc)
 {
 	spin_lock(&irq_mapping_update_lock);
  
-	*irq = find_unbound_irq();
-	if (*irq == -1)
-		goto out;
+	if (alloc & XEN_ALLOC_IRQ) {
+		*irq = find_unbound_irq();
+		if (*irq == -1)
+			goto out;
+	}
  
-	*pirq = find_unbound_pirq(MAP_PIRQ_TYPE_MSI);
-	if (*pirq == -1)
-		goto out;
+	if (alloc & XEN_ALLOC_PIRQ) {
+		*pirq = find_unbound_pirq(MAP_PIRQ_TYPE_MSI);
+		if (*pirq == -1)
+			goto out;
+	}
  
 	set_irq_chip_and_handler_name(*irq, &xen_pirq_chip,
 				      handle_level_irq, name);
@@ -766,6 +770,7 @@
 			printk(KERN_WARNING "unmap irq failed %d\n", rc);
 			goto out;
 		}
+		pirq_to_irq[info->u.pirq.pirq] = -1;
 	}
 	irq_info[irq] = mk_unbound_info();
  
@@ -784,6 +789,11 @@
 int xen_gsi_from_irq(unsigned irq)
 {
 	return gsi_from_irq(irq);
+}
+
+int xen_irq_from_pirq(unsigned pirq)
+{
+	return pirq_to_irq[pirq];
 }
  
 int bind_evtchn_to_irq(unsigned int evtchn)
@@ -76,7 +76,9 @@
  
 #ifdef CONFIG_PCI_MSI
 /* Allocate an irq and a pirq to be used with MSIs. */
-void xen_allocate_pirq_msi(char *name, int *irq, int *pirq);
+#define XEN_ALLOC_PIRQ (1 << 0)
+#define XEN_ALLOC_IRQ  (1 << 1)
+void xen_allocate_pirq_msi(char *name, int *irq, int *pirq, int alloc_mask);
 int xen_create_msi_irq(struct pci_dev *dev, struct msi_desc *msidesc, int type);
 #endif
  
@@ -88,6 +90,9 @@
  
 /* Return gsi allocated to pirq */
 int xen_gsi_from_irq(unsigned pirq);
+
+/* Return irq from pirq */
+int xen_irq_from_pirq(unsigned pirq);
  
 #endif	/* _XEN_EVENTS_H */
...	...	@@ -70,6 +70,9 @@
70	70	struct xen_pci_frontend_ops *xen_pci_frontend;
71	71	EXPORT_SYMBOL_GPL(xen_pci_frontend);
72	72
	73	+#define XEN_PIRQ_MSI_DATA (MSI_DATA_TRIGGER_EDGE \| \
	74	+ MSI_DATA_LEVEL_ASSERT \| (3 << 8) \| MSI_DATA_VECTOR(0))
	75	+
73	76	static void xen_msi_compose_msg(struct pci_dev *pdev, unsigned int pirq,
74	77	struct msi_msg *msg)
75	78	{
...	...	@@ -83,12 +86,7 @@
83	86	MSI_ADDR_REDIRECTION_CPU \|
84	87	MSI_ADDR_DEST_ID(pirq);
85	88
86		- msg->data =
87		- MSI_DATA_TRIGGER_EDGE \|
88		- MSI_DATA_LEVEL_ASSERT \|
89		- /* delivery mode reserved */
90		- (3 << 8) \|
91		- MSI_DATA_VECTOR(0);
	89	+ msg->data = XEN_PIRQ_MSI_DATA;
92	90	}
93	91
94	92	static int xen_hvm_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
95	93
...	...	@@ -98,8 +96,23 @@
98	96	struct msi_msg msg;
99	97
100	98	list_for_each_entry(msidesc, &dev->msi_list, list) {
	99	+ __read_msi_msg(msidesc, &msg);
	100	+ pirq = MSI_ADDR_EXT_DEST_ID(msg.address_hi) \|
	101	+ ((msg.address_lo >> MSI_ADDR_DEST_ID_SHIFT) & 0xff);
	102	+ if (xen_irq_from_pirq(pirq) >= 0 && msg.data == XEN_PIRQ_MSI_DATA) {
	103	+ xen_allocate_pirq_msi((type == PCI_CAP_ID_MSIX) ?
	104	+ "msi-x" : "msi", &irq, &pirq, XEN_ALLOC_IRQ);
	105	+ if (irq < 0)
	106	+ goto error;
	107	+ ret = set_irq_msi(irq, msidesc);
	108	+ if (ret < 0)
	109	+ goto error_while;
	110	+ printk(KERN_DEBUG "xen: msi already setup: msi --> irq=%d"
	111	+ " pirq=%d\n", irq, pirq);
	112	+ return 0;
	113	+ }
101	114	xen_allocate_pirq_msi((type == PCI_CAP_ID_MSIX) ?
102		- "msi-x" : "msi", &irq, &pirq);
	115	+ "msi-x" : "msi", &irq, &pirq, (XEN_ALLOC_IRQ \| XEN_ALLOC_PIRQ));
103	116	if (irq < 0 \|\| pirq < 0)
104	117	goto error;
105	118	printk(KERN_DEBUG "xen: msi --> irq=%d, pirq=%d\n", irq, pirq);
...	...	@@ -668,17 +668,21 @@
668	668	#include <linux/msi.h>
669	669	#include "../pci/msi.h"
670	670
671		-void xen_allocate_pirq_msi(char name, int irq, int *pirq)
	671	+void xen_allocate_pirq_msi(char name, int irq, int *pirq, int alloc)
672	672	{
673	673	spin_lock(&irq_mapping_update_lock);
674	674
675		- *irq = find_unbound_irq();
676		- if (*irq == -1)
677		- goto out;
	675	+ if (alloc & XEN_ALLOC_IRQ) {
	676	+ *irq = find_unbound_irq();
	677	+ if (*irq == -1)
	678	+ goto out;
	679	+ }
678	680
679		- *pirq = find_unbound_pirq(MAP_PIRQ_TYPE_MSI);
680		- if (*pirq == -1)
681		- goto out;
	681	+ if (alloc & XEN_ALLOC_PIRQ) {
	682	+ *pirq = find_unbound_pirq(MAP_PIRQ_TYPE_MSI);
	683	+ if (*pirq == -1)
	684	+ goto out;
	685	+ }
682	686
683	687	set_irq_chip_and_handler_name(*irq, &xen_pirq_chip,
684	688	handle_level_irq, name);
...	...	@@ -766,6 +770,7 @@
766	770	printk(KERN_WARNING "unmap irq failed %d\n", rc);
767	771	goto out;
768	772	}
	773	+ pirq_to_irq[info->u.pirq.pirq] = -1;
769	774	}
770	775	irq_info[irq] = mk_unbound_info();
771	776
...	...	@@ -784,6 +789,11 @@
784	789	int xen_gsi_from_irq(unsigned irq)
785	790	{
786	791	return gsi_from_irq(irq);
	792	+}
	793	+
	794	+int xen_irq_from_pirq(unsigned pirq)
	795	+{
	796	+ return pirq_to_irq[pirq];
787	797	}
788	798
789	799	int bind_evtchn_to_irq(unsigned int evtchn)
...	...	@@ -76,7 +76,9 @@
76	76
77	77	#ifdef CONFIG_PCI_MSI
78	78	/* Allocate an irq and a pirq to be used with MSIs. */
79		-void xen_allocate_pirq_msi(char name, int irq, int *pirq);
	79	+#define XEN_ALLOC_PIRQ (1 << 0)
	80	+#define XEN_ALLOC_IRQ (1 << 1)
	81	+void xen_allocate_pirq_msi(char name, int irq, int *pirq, int alloc_mask);
80	82	int xen_create_msi_irq(struct pci_dev dev, struct msi_desc msidesc, int type);
81	83	#endif
82	84
...	...	@@ -88,6 +90,9 @@
88	90
89	91	/* Return gsi allocated to pirq */
90	92	int xen_gsi_from_irq(unsigned pirq);
	93	+
	94	+/* Return irq from pirq */
	95	+int xen_irq_from_pirq(unsigned pirq);
91	96
92	97	#endif /* _XEN_EVENTS_H */