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Subject[ 72/91] xen: do not map the same GSI twice in PVHVM guests.
3.4-stable review patch.  If anyone has any objections, please let me know.

------------------
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

commit 68c2c39a76b094e9b2773e5846424ea674bf2c46 upstream.

PV on HVM guests map GSIs into event channels. At restore time the
event channels are resumed by restore_pirqs.

Device drivers might try to register the same GSI again through ACPI at
restore time, but the GSI has already been mapped and bound by
restore_pirqs. This patch detects these situations and avoids
mapping the same GSI multiple times.

Without this patch we get:
(XEN) irq.c:2235: dom4: pirq 23 or emuirq 28 already mapped
and waste a pirq.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/pci/xen.c | 4 ++++
drivers/xen/events.c | 5 +++--
include/xen/events.h | 3 +++
3 files changed, 10 insertions(+), 2 deletions(-)
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -64,6 +64,10 @@ static int xen_register_pirq(u32 gsi, in
int shareable = 0;
char *name;

+ irq = xen_irq_from_gsi(gsi);
+ if (irq > 0)
+ return irq;
+
if (set_pirq)
pirq = gsi;

--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -611,7 +611,7 @@ static void disable_pirq(struct irq_data
disable_dynirq(data);
}

-static int find_irq_by_gsi(unsigned gsi)
+int xen_irq_from_gsi(unsigned gsi)
{
struct irq_info *info;

@@ -625,6 +625,7 @@ static int find_irq_by_gsi(unsigned gsi)

return -1;
}
+EXPORT_SYMBOL_GPL(xen_irq_from_gsi);

/*
* Do not make any assumptions regarding the relationship between the
@@ -644,7 +645,7 @@ int xen_bind_pirq_gsi_to_irq(unsigned gs

mutex_lock(&irq_mapping_update_lock);

- irq = find_irq_by_gsi(gsi);
+ irq = xen_irq_from_gsi(gsi);
if (irq != -1) {
printk(KERN_INFO "xen_map_pirq_gsi: returning irq %d for gsi %u\n",
irq, gsi);
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -103,6 +103,9 @@ int xen_irq_from_pirq(unsigned pirq);
/* Return the pirq allocated to the irq. */
int xen_pirq_from_irq(unsigned irq);

+/* Return the irq allocated to the gsi */
+int xen_irq_from_gsi(unsigned gsi);
+
/* Determine whether to ignore this IRQ if it is passed to a guest. */
int xen_test_irq_shared(int irq);




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