[PATCH] xen: use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq

[PATCH] xen: use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq

[Stefano Stabellini]

Use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq

Use the new hypercall PHYSDEVOP_get_free_pirq to ask Xen to allocate a
pirq. Remove the unsupported PHYSDEVOP_get_nr_pirqs hypercall to get the
amount of pirq available.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 321a0c8..ffd286e 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -382,12 +382,17 @@ static int get_nr_hw_irqs(void)
 	return ret;
 }
 
-/* callers of this function should make sure that PHYSDEVOP_get_nr_pirqs
- * succeeded otherwise nr_pirqs won't hold the right value */
-static int find_unbound_pirq(void)
+static int find_unbound_pirq(int type)
 {
-	int i;
-	for (i = nr_pirqs-1; i >= 0; i--) {
+	int rc, i;
+	struct physdev_get_free_pirq op_get_free_pirq;
+	op_get_free_pirq.type = type;
+
+	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_free_pirq, &op_get_free_pirq);
+	if (!rc)
+		return op_get_free_pirq.pirq;
+
+	for (i = 16; i <= nr_pirqs-1; i++) {
 		if (pirq_to_irq[i] < 0)
 			return i;
 	}
@@ -669,7 +674,7 @@ void xen_allocate_pirq_msi(char *name, int *irq, int *pirq)
 	if (*irq == -1)
 		goto out;
 
-	*pirq = find_unbound_pirq();
+	*pirq = find_unbound_pirq(MAP_PIRQ_TYPE_MSI);
 	if (*pirq == -1)
 		goto out;
 
@@ -1504,23 +1509,12 @@ void xen_callback_vector(void) {}
 void __init xen_init_IRQ(void)
 {
 	int i, rc;
-	struct physdev_nr_pirqs op_nr_pirqs;
 
 	cpu_evtchn_mask_p = kcalloc(nr_cpu_ids, sizeof(struct cpu_evtchn_s),
 				    GFP_KERNEL);
 	irq_info = kcalloc(nr_irqs, sizeof(*irq_info), GFP_KERNEL);
 
-	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_nr_pirqs, &op_nr_pirqs);
-	if (rc < 0) {
-		nr_pirqs = nr_irqs;
-		if (rc != -ENOSYS)
-			printk(KERN_WARNING "PHYSDEVOP_get_nr_pirqs returned rc=%d\n", rc);
-	} else {
-		if (xen_pv_domain() && !xen_initial_domain())
-			nr_pirqs = max((int)op_nr_pirqs.nr_pirqs, nr_irqs);
-		else
-			nr_pirqs = op_nr_pirqs.nr_pirqs;
-	}
+	nr_pirqs = nr_irqs;
 	pirq_to_irq = kcalloc(nr_pirqs, sizeof(*pirq_to_irq), GFP_KERNEL);
 	for (i = 0; i < nr_pirqs; i++)
 		pirq_to_irq[i] = -1;
diff --git a/include/xen/interface/physdev.h b/include/xen/interface/physdev.h
index 2b2c66c..534cac8 100644
--- a/include/xen/interface/physdev.h
+++ b/include/xen/interface/physdev.h
@@ -188,6 +188,16 @@ struct physdev_nr_pirqs {
     uint32_t nr_pirqs;
 };
 
+/* type is MAP_PIRQ_TYPE_GSI or MAP_PIRQ_TYPE_MSI
+ * the hypercall returns a free pirq */
+#define PHYSDEVOP_get_free_pirq    23
+struct physdev_get_free_pirq {
+    /* IN */ 
+    int type;
+    /* OUT */
+    uint32_t pirq;
+};
+
 /*
  * Notify that some PIRQ-bound event channels have been unmasked.
  * ** This command is obsolete since interface version 0x00030202 and is **

Re: [PATCH] xen: use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq

[Konrad Rzeszutek Wilk]

On Fri, Nov 19, 2010 at 01:58:03PM +0000, Stefano Stabellini wrote:
> Use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq
> 
> Use the new hypercall PHYSDEVOP_get_free_pirq to ask Xen to allocate a
> pirq. Remove the unsupported PHYSDEVOP_get_nr_pirqs hypercall to get the
> amount of pirq available.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> 
> diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> index 321a0c8..ffd286e 100644
> --- a/drivers/xen/events.c
> +++ b/drivers/xen/events.c
> @@ -382,12 +382,17 @@ static int get_nr_hw_irqs(void)
>  	return ret;
>  }
>  
> -/* callers of this function should make sure that PHYSDEVOP_get_nr_pirqs
> - * succeeded otherwise nr_pirqs won't hold the right value */
> -static int find_unbound_pirq(void)
> +static int find_unbound_pirq(int type)
>  {
> -	int i;
> -	for (i = nr_pirqs-1; i >= 0; i--) {
> +	int rc, i;
> +	struct physdev_get_free_pirq op_get_free_pirq;
> +	op_get_free_pirq.type = type;
> +
> +	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_free_pirq, &op_get_free_pirq);
> +	if (!rc)
> +		return op_get_free_pirq.pirq;
> +
> +	for (i = 16; i <= nr_pirqs-1; i++) {

16? No no. Why not re-use the old loop, like so:

 	for (i = nr_pirqs-1; i >= 0; i--) {

>  		if (pirq_to_irq[i] < 0)
>  			return i;
>  	}
> @@ -669,7 +674,7 @@ void xen_allocate_pirq_msi(char *name, int *irq, int *pirq)
>  	if (*irq == -1)
>  		goto out;
>  
> -	*pirq = find_unbound_pirq();
> +	*pirq = find_unbound_pirq(MAP_PIRQ_TYPE_MSI);
>  	if (*pirq == -1)
>  		goto out;
>  
> @@ -1504,23 +1509,12 @@ void xen_callback_vector(void) {}
>  void __init xen_init_IRQ(void)
>  {
>  	int i, rc;
> -	struct physdev_nr_pirqs op_nr_pirqs;
>  
>  	cpu_evtchn_mask_p = kcalloc(nr_cpu_ids, sizeof(struct cpu_evtchn_s),
>  				    GFP_KERNEL);
>  	irq_info = kcalloc(nr_irqs, sizeof(*irq_info), GFP_KERNEL);
>  
> -	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_nr_pirqs, &op_nr_pirqs);
> -	if (rc < 0) {
> -		nr_pirqs = nr_irqs;
> -		if (rc != -ENOSYS)
> -			printk(KERN_WARNING "PHYSDEVOP_get_nr_pirqs returned rc=%d\n", rc);
> -	} else {
> -		if (xen_pv_domain() && !xen_initial_domain())
> -			nr_pirqs = max((int)op_nr_pirqs.nr_pirqs, nr_irqs);
> -		else
> -			nr_pirqs = op_nr_pirqs.nr_pirqs;
> -	}
> +	nr_pirqs = nr_irqs;

Why not just get rid of nr_pirgs altogether then? And use 'nr_irqs' instead?

Re: [PATCH] xen: use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq

[Stefano Stabellini]

On Fri, 19 Nov 2010, Konrad Rzeszutek Wilk wrote:
> On Fri, Nov 19, 2010 at 01:58:03PM +0000, Stefano Stabellini wrote:
> > Use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq
> > 
> > Use the new hypercall PHYSDEVOP_get_free_pirq to ask Xen to allocate a
> > pirq. Remove the unsupported PHYSDEVOP_get_nr_pirqs hypercall to get the
> > amount of pirq available.
> > 
> > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > 
> > diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> > index 321a0c8..ffd286e 100644
> > --- a/drivers/xen/events.c
> > +++ b/drivers/xen/events.c
> > @@ -382,12 +382,17 @@ static int get_nr_hw_irqs(void)
> >  	return ret;
> >  }
> >  
> > -/* callers of this function should make sure that PHYSDEVOP_get_nr_pirqs
> > - * succeeded otherwise nr_pirqs won't hold the right value */
> > -static int find_unbound_pirq(void)
> > +static int find_unbound_pirq(int type)
> >  {
> > -	int i;
> > -	for (i = nr_pirqs-1; i >= 0; i--) {
> > +	int rc, i;
> > +	struct physdev_get_free_pirq op_get_free_pirq;
> > +	op_get_free_pirq.type = type;
> > +
> > +	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_free_pirq, &op_get_free_pirq);
> > +	if (!rc)
> > +		return op_get_free_pirq.pirq;
> > +
> > +	for (i = 16; i <= nr_pirqs-1; i++) {
> 
> 16? No no. Why not re-use the old loop, like so:
> 
>  	for (i = nr_pirqs-1; i >= 0; i--) {
> 

Because we don't know the real nr_pirqs anymore (PHYSDEVOP_get_nr_pirqs
has been removed), so it is highly possible that starting from the top
down would give us pirq numbers out of range in Xen.  Therefore we need
to start from the bottom up, and the bottom for Xen is 16.


> >  		if (pirq_to_irq[i] < 0)
> >  			return i;
> >  	}
> > @@ -669,7 +674,7 @@ void xen_allocate_pirq_msi(char *name, int *irq, int *pirq)
> >  	if (*irq == -1)
> >  		goto out;
> >  
> > -	*pirq = find_unbound_pirq();
> > +	*pirq = find_unbound_pirq(MAP_PIRQ_TYPE_MSI);
> >  	if (*pirq == -1)
> >  		goto out;
> >  
> > @@ -1504,23 +1509,12 @@ void xen_callback_vector(void) {}
> >  void __init xen_init_IRQ(void)
> >  {
> >  	int i, rc;
> > -	struct physdev_nr_pirqs op_nr_pirqs;
> >  
> >  	cpu_evtchn_mask_p = kcalloc(nr_cpu_ids, sizeof(struct cpu_evtchn_s),
> >  				    GFP_KERNEL);
> >  	irq_info = kcalloc(nr_irqs, sizeof(*irq_info), GFP_KERNEL);
> >  
> > -	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_nr_pirqs, &op_nr_pirqs);
> > -	if (rc < 0) {
> > -		nr_pirqs = nr_irqs;
> > -		if (rc != -ENOSYS)
> > -			printk(KERN_WARNING "PHYSDEVOP_get_nr_pirqs returned rc=%d\n", rc);
> > -	} else {
> > -		if (xen_pv_domain() && !xen_initial_domain())
> > -			nr_pirqs = max((int)op_nr_pirqs.nr_pirqs, nr_irqs);
> > -		else
> > -			nr_pirqs = op_nr_pirqs.nr_pirqs;
> > -	}
> > +	nr_pirqs = nr_irqs;
> 
> Why not just get rid of nr_pirgs altogether then? And use 'nr_irqs' instead?
> 

Yeah, I guess we could do that. I kept it around just to make it more
obvious that the max pirq number is different from nr_irqs and we don't
know what the exact value is.

Re: [PATCH] xen: use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq

[Konrad Rzeszutek Wilk]

On Sat, Nov 20, 2010 at 01:19:31AM +0000, Stefano Stabellini wrote:
> On Fri, 19 Nov 2010, Konrad Rzeszutek Wilk wrote:
> > On Fri, Nov 19, 2010 at 01:58:03PM +0000, Stefano Stabellini wrote:
> > > Use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq
> > > 
> > > Use the new hypercall PHYSDEVOP_get_free_pirq to ask Xen to allocate a
> > > pirq. Remove the unsupported PHYSDEVOP_get_nr_pirqs hypercall to get the
> > > amount of pirq available.
> > > 
> > > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > > 
> > > diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> > > index 321a0c8..ffd286e 100644
> > > --- a/drivers/xen/events.c
> > > +++ b/drivers/xen/events.c
> > > @@ -382,12 +382,17 @@ static int get_nr_hw_irqs(void)
> > >  	return ret;
> > >  }
> > >  
> > > -/* callers of this function should make sure that PHYSDEVOP_get_nr_pirqs
> > > - * succeeded otherwise nr_pirqs won't hold the right value */
> > > -static int find_unbound_pirq(void)
> > > +static int find_unbound_pirq(int type)
> > >  {
> > > -	int i;
> > > -	for (i = nr_pirqs-1; i >= 0; i--) {
> > > +	int rc, i;
> > > +	struct physdev_get_free_pirq op_get_free_pirq;
> > > +	op_get_free_pirq.type = type;
> > > +
> > > +	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_free_pirq, &op_get_free_pirq);
> > > +	if (!rc)
> > > +		return op_get_free_pirq.pirq;
> > > +
> > > +	for (i = 16; i <= nr_pirqs-1; i++) {
> > 
> > 16? No no. Why not re-use the old loop, like so:
> > 
> >  	for (i = nr_pirqs-1; i >= 0; i--) {
> > 
> 
> Because we don't know the real nr_pirqs anymore (PHYSDEVOP_get_nr_pirqs
> has been removed), so it is highly possible that starting from the top
> down would give us pirq numbers out of range in Xen.  Therefore we need
> to start from the bottom up, and the bottom for Xen is 16.

Right, I forgot about the hypercall call. How about using LEGACY_IRQ instead then?

> 
> 
> > >  		if (pirq_to_irq[i] < 0)
> > >  			return i;
> > >  	}
> > > @@ -669,7 +674,7 @@ void xen_allocate_pirq_msi(char *name, int *irq, int *pirq)
> > >  	if (*irq == -1)
> > >  		goto out;
> > >  
> > > -	*pirq = find_unbound_pirq();
> > > +	*pirq = find_unbound_pirq(MAP_PIRQ_TYPE_MSI);
> > >  	if (*pirq == -1)
> > >  		goto out;
> > >  
> > > @@ -1504,23 +1509,12 @@ void xen_callback_vector(void) {}
> > >  void __init xen_init_IRQ(void)
> > >  {
> > >  	int i, rc;
> > > -	struct physdev_nr_pirqs op_nr_pirqs;
> > >  
> > >  	cpu_evtchn_mask_p = kcalloc(nr_cpu_ids, sizeof(struct cpu_evtchn_s),
> > >  				    GFP_KERNEL);
> > >  	irq_info = kcalloc(nr_irqs, sizeof(*irq_info), GFP_KERNEL);
> > >  
> > > -	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_nr_pirqs, &op_nr_pirqs);
> > > -	if (rc < 0) {
> > > -		nr_pirqs = nr_irqs;
> > > -		if (rc != -ENOSYS)
> > > -			printk(KERN_WARNING "PHYSDEVOP_get_nr_pirqs returned rc=%d\n", rc);
> > > -	} else {
> > > -		if (xen_pv_domain() && !xen_initial_domain())
> > > -			nr_pirqs = max((int)op_nr_pirqs.nr_pirqs, nr_irqs);
> > > -		else
> > > -			nr_pirqs = op_nr_pirqs.nr_pirqs;
> > > -	}
> > > +	nr_pirqs = nr_irqs;
> > 
> > Why not just get rid of nr_pirgs altogether then? And use 'nr_irqs' instead?
> > 
> 
> Yeah, I guess we could do that. I kept it around just to make it more
> obvious that the max pirq number is different from nr_irqs and we don't
> know what the exact value is.


But with this change it is the same, is it not?

	"nr_pirgs = nr_irqs;"

Or when you say "max pirq" you are referring to something else altogether?

Re: [PATCH] xen: use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq

[Stefano Stabellini]

On Mon, 22 Nov 2010, Konrad Rzeszutek Wilk wrote:
> On Sat, Nov 20, 2010 at 01:19:31AM +0000, Stefano Stabellini wrote:
> > On Fri, 19 Nov 2010, Konrad Rzeszutek Wilk wrote:
> > > On Fri, Nov 19, 2010 at 01:58:03PM +0000, Stefano Stabellini wrote:
> > > > Use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq
> > > > 
> > > > Use the new hypercall PHYSDEVOP_get_free_pirq to ask Xen to allocate a
> > > > pirq. Remove the unsupported PHYSDEVOP_get_nr_pirqs hypercall to get the
> > > > amount of pirq available.
> > > > 
> > > > Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > > > 
> > > > diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> > > > index 321a0c8..ffd286e 100644
> > > > --- a/drivers/xen/events.c
> > > > +++ b/drivers/xen/events.c
> > > > @@ -382,12 +382,17 @@ static int get_nr_hw_irqs(void)
> > > >  	return ret;
> > > >  }
> > > >  
> > > > -/* callers of this function should make sure that PHYSDEVOP_get_nr_pirqs
> > > > - * succeeded otherwise nr_pirqs won't hold the right value */
> > > > -static int find_unbound_pirq(void)
> > > > +static int find_unbound_pirq(int type)
> > > >  {
> > > > -	int i;
> > > > -	for (i = nr_pirqs-1; i >= 0; i--) {
> > > > +	int rc, i;
> > > > +	struct physdev_get_free_pirq op_get_free_pirq;
> > > > +	op_get_free_pirq.type = type;
> > > > +
> > > > +	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_free_pirq, &op_get_free_pirq);
> > > > +	if (!rc)
> > > > +		return op_get_free_pirq.pirq;
> > > > +
> > > > +	for (i = 16; i <= nr_pirqs-1; i++) {
> > > 
> > > 16? No no. Why not re-use the old loop, like so:
> > > 
> > >  	for (i = nr_pirqs-1; i >= 0; i--) {
> > > 
> > 
> > Because we don't know the real nr_pirqs anymore (PHYSDEVOP_get_nr_pirqs
> > has been removed), so it is highly possible that starting from the top
> > down would give us pirq numbers out of range in Xen.  Therefore we need
> > to start from the bottom up, and the bottom for Xen is 16.
> 
> Right, I forgot about the hypercall call. How about using LEGACY_IRQ instead then?
> 

Do you mean NR_IRQS_LEGACY? Yeah, I could do that.

> > 
> > 
> > > >  		if (pirq_to_irq[i] < 0)
> > > >  			return i;
> > > >  	}
> > > > @@ -669,7 +674,7 @@ void xen_allocate_pirq_msi(char *name, int *irq, int *pirq)
> > > >  	if (*irq == -1)
> > > >  		goto out;
> > > >  
> > > > -	*pirq = find_unbound_pirq();
> > > > +	*pirq = find_unbound_pirq(MAP_PIRQ_TYPE_MSI);
> > > >  	if (*pirq == -1)
> > > >  		goto out;
> > > >  
> > > > @@ -1504,23 +1509,12 @@ void xen_callback_vector(void) {}
> > > >  void __init xen_init_IRQ(void)
> > > >  {
> > > >  	int i, rc;
> > > > -	struct physdev_nr_pirqs op_nr_pirqs;
> > > >  
> > > >  	cpu_evtchn_mask_p = kcalloc(nr_cpu_ids, sizeof(struct cpu_evtchn_s),
> > > >  				    GFP_KERNEL);
> > > >  	irq_info = kcalloc(nr_irqs, sizeof(*irq_info), GFP_KERNEL);
> > > >  
> > > > -	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_nr_pirqs, &op_nr_pirqs);
> > > > -	if (rc < 0) {
> > > > -		nr_pirqs = nr_irqs;
> > > > -		if (rc != -ENOSYS)
> > > > -			printk(KERN_WARNING "PHYSDEVOP_get_nr_pirqs returned rc=%d\n", rc);
> > > > -	} else {
> > > > -		if (xen_pv_domain() && !xen_initial_domain())
> > > > -			nr_pirqs = max((int)op_nr_pirqs.nr_pirqs, nr_irqs);
> > > > -		else
> > > > -			nr_pirqs = op_nr_pirqs.nr_pirqs;
> > > > -	}
> > > > +	nr_pirqs = nr_irqs;
> > > 
> > > Why not just get rid of nr_pirgs altogether then? And use 'nr_irqs' instead?
> > > 
> > 
> > Yeah, I guess we could do that. I kept it around just to make it more
> > obvious that the max pirq number is different from nr_irqs and we don't
> > know what the exact value is.
> 
> 
> But with this change it is the same, is it not?
> 
> 	"nr_pirgs = nr_irqs;"
> 
> Or when you say "max pirq" you are referring to something else altogether?
> 

Yes, it is the same. I guess a comment would be better then.

Appended the updated version of this patch.

---

Use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq

Use the new hypercall PHYSDEVOP_get_free_pirq to ask Xen to allocate a
pirq. Remove the unsupported PHYSDEVOP_get_nr_pirqs hypercall to get the
amount of pirq available.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>


diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 2811bb9..9f19daa 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -105,7 +105,6 @@ struct irq_info
 
 static struct irq_info *irq_info;
 static int *pirq_to_irq;
-static int nr_pirqs;
 
 static int *evtchn_to_irq;
 struct cpu_evtchn_s {
@@ -385,12 +384,17 @@ static int get_nr_hw_irqs(void)
 	return ret;
 }
 
-/* callers of this function should make sure that PHYSDEVOP_get_nr_pirqs
- * succeeded otherwise nr_pirqs won't hold the right value */
-static int find_unbound_pirq(void)
+static int find_unbound_pirq(int type)
 {
-	int i;
-	for (i = nr_pirqs-1; i >= 0; i--) {
+	int rc, i;
+	struct physdev_get_free_pirq op_get_free_pirq;
+	op_get_free_pirq.type = type;
+
+	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_free_pirq, &op_get_free_pirq);
+	if (!rc)
+		return op_get_free_pirq.pirq;
+
+	for (i = NR_IRQS_LEGACY; i <= nr_irqs-1; i++) {
 		if (pirq_to_irq[i] < 0)
 			return i;
 	}
@@ -611,9 +615,9 @@ int xen_map_pirq_gsi(unsigned pirq, unsigned gsi, int shareable, char *name)
 
 	spin_lock(&irq_mapping_update_lock);
 
-	if ((pirq > nr_pirqs) || (gsi > nr_irqs)) {
+	if ((pirq > nr_irqs) || (gsi > nr_irqs)) {
 		printk(KERN_WARNING "xen_map_pirq_gsi: %s %s is incorrect!\n",
-			pirq > nr_pirqs ? "nr_pirqs" :"",
+			pirq > nr_irqs ? "nr_pirqs" :"",
 			gsi > nr_irqs ? "nr_irqs" : "");
 		goto out;
 	}
@@ -672,7 +676,7 @@ void xen_allocate_pirq_msi(char *name, int *irq, int *pirq)
 	if (*irq == -1)
 		goto out;
 
-	*pirq = find_unbound_pirq();
+	*pirq = find_unbound_pirq(MAP_PIRQ_TYPE_MSI);
 	if (*pirq == -1)
 		goto out;
 
@@ -1506,26 +1510,17 @@ void xen_callback_vector(void) {}
 
 void __init xen_init_IRQ(void)
 {
-	int i, rc;
-	struct physdev_nr_pirqs op_nr_pirqs;
+	int i;
 
 	cpu_evtchn_mask_p = kcalloc(nr_cpu_ids, sizeof(struct cpu_evtchn_s),
 				    GFP_KERNEL);
 	irq_info = kcalloc(nr_irqs, sizeof(*irq_info), GFP_KERNEL);
 
-	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_nr_pirqs, &op_nr_pirqs);
-	if (rc < 0) {
-		nr_pirqs = nr_irqs;
-		if (rc != -ENOSYS)
-			printk(KERN_WARNING "PHYSDEVOP_get_nr_pirqs returned rc=%d\n", rc);
-	} else {
-		if (xen_pv_domain() && !xen_initial_domain())
-			nr_pirqs = max((int)op_nr_pirqs.nr_pirqs, nr_irqs);
-		else
-			nr_pirqs = op_nr_pirqs.nr_pirqs;
-	}
-	pirq_to_irq = kcalloc(nr_pirqs, sizeof(*pirq_to_irq), GFP_KERNEL);
-	for (i = 0; i < nr_pirqs; i++)
+	/* We are using nr_irqs as the maximum number of pirq available but
+	 * that number is actually chosen by Xen and we don't know exactly
+	 * what it is. Be careful choosing high pirq numbers. */
+	pirq_to_irq = kcalloc(nr_irqs, sizeof(*pirq_to_irq), GFP_KERNEL);
+	for (i = 0; i < nr_irqs; i++)
 		pirq_to_irq[i] = -1;
 
 	evtchn_to_irq = kcalloc(NR_EVENT_CHANNELS, sizeof(*evtchn_to_irq),
diff --git a/include/xen/interface/physdev.h b/include/xen/interface/physdev.h
index 2b2c66c..534cac8 100644
--- a/include/xen/interface/physdev.h
+++ b/include/xen/interface/physdev.h
@@ -188,6 +188,16 @@ struct physdev_nr_pirqs {
     uint32_t nr_pirqs;
 };
 
+/* type is MAP_PIRQ_TYPE_GSI or MAP_PIRQ_TYPE_MSI
+ * the hypercall returns a free pirq */
+#define PHYSDEVOP_get_free_pirq    23
+struct physdev_get_free_pirq {
+    /* IN */ 
+    int type;
+    /* OUT */
+    uint32_t pirq;
+};
+
 /*
  * Notify that some PIRQ-bound event channels have been unmasked.
  * ** This command is obsolete since interface version 0x00030202 and is **