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Re: [Xen-devel] [PATCH v2 06/21] xen/arm: Allow virq != irq

Hi Ian,

On 09/09/14 06:29, Ian Campbell wrote:
Mostly spelling/grammar nits, a couple of questions but mostly looks

On Thu, 2014-07-31 at 16:00 +0100, Julien Grall wrote:
Actually Xen is assuming that the virtual IRQ will always be equal the IRQ.

"be equal to" or better "always be the same as".

Modify, route_guest_irq to take the virtual IRQ in parameter and let Xen

Spurious comma.

assigned a different IRQ number. Also store the vIRQ in the desc action to


retrieve easily the IRQ target when we need to inject the interrupt.

"easily retrieve" (or "be able to easily retrieve")

As DOM0 will get most the device, the vIRQ is equal to the IRQ.

"most of the devices".

I suppose the sentence should end with "in that case" or something?

Yes. I will fix all the grammar nits in the next version.

@@ -122,18 +129,20 @@ void __cpuinit init_secondary_IRQ(void)
      BUG_ON(init_local_irq_data() < 0);

-static inline struct domain *irq_get_domain(struct irq_desc *desc)
+static inline struct irq_guest *irq_get_guest_info(struct irq_desc *desc)
-    if ( !test_bit(_IRQ_GUEST, &desc->status) )
-        return dom_xen;
+    ASSERT(test_bit(_IRQ_GUEST, &desc->status));
      ASSERT(desc->action != NULL);

      return desc->action->dev_id;

+static inline struct domain *irq_get_domain(struct irq_desc *desc)
+    return irq_get_guest_info(desc)->d;

Previously irq_get_domain could return dom_xen for !_IRQ_GUEST domains.
What happened to this logic? If it is never possible to get here with a
Xen owned IRQ then I think that is worth mentioning in the commit log
and/or a comment.

This was a safe guard in case of developer were misusing the function. Actually every callers of this function are checking that the IRQ is assigned to a guest before calling irq_get_domain.

I will mention it in the commit log.

@@ -206,7 +215,7 @@ void do_IRQ(struct cpu_user_regs *regs, unsigned int irq, 
int is_fiq)

          /* the irq cannot be a PPI, we only support delivery of SPIs to
           * guests */
-        vgic_vcpu_inject_spi(d, irq);
+        vgic_vcpu_inject_spi(info->d, info->virq);

Could this function take an irq_guest* or are there other callers?

I haven't thought about this possibility. This is the only caller, so I will pass irq_guest.


Julien Grall

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