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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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