[Xen-devel] [PATCH RFC 5/6] xen/arm: Add function to query IRQ 'ownership'.

[Kyle Temkin <kyle@xxxxxxxxxxx>]

From: "Kyle J. Temkin" <temkink@xxxxxxxxxxxx>

The addition of new IRQ-related platform hooks now allow platforms to
perform platform-specific interrupt logic; allowing e.g. virtualization
of platform-specific interrupt controller hardware.

This commit adds the ability to for the platform to identify the domain
a given IRQ routes to, allowing platform logic to e.g. deny access to
registers associated with a given IRQ unless the requesting domain
'owns' the IRQ. This will be used on Tegra platforms, where the hardware
domain needs access to its legacy interrupt controller, but should not
be able to control registers that correspond to other domains' IRQs, or
sections associated with IRQs routed to Xen.

Signed-off-by: Kyle Temkin <temkink@xxxxxxxxxxxx>
---
 xen/arch/arm/irq.c        | 10 ++++++++++
 xen/include/asm-arm/irq.h |  2 ++
 2 files changed, 12 insertions(+)

diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
index dc42817..c6e1a24 100644
--- a/xen/arch/arm/irq.c
+++ b/xen/arch/arm/irq.c
@@ -144,6 +144,16 @@ static inline struct domain *irq_get_domain(struct 
irq_desc *desc)
     return irq_get_guest_info(desc)->d;
 }
 
+domid_t irq_get_domain_id(struct irq_desc *desc)
+{
+    // If this domain isn't routed to a guest, return DOMID_XEN.
+    if(!test_bit(_IRQ_GUEST, &desc->status))
+        return DOMID_XEN;
+
+    // Otherise, get the guest domain's information.
+    return irq_get_domain(desc)->domain_id;
+}
+
 void irq_set_affinity(struct irq_desc *desc, const cpumask_t *cpu_mask)
 {
     if ( desc != NULL )
diff --git a/xen/include/asm-arm/irq.h b/xen/include/asm-arm/irq.h
index 8f7a167..55300a8 100644
--- a/xen/include/asm-arm/irq.h
+++ b/xen/include/asm-arm/irq.h
@@ -45,6 +45,8 @@ int route_irq_to_guest(struct domain *d, unsigned int virq,
                        unsigned int irq, const char *devname);
 int release_guest_irq(struct domain *d, unsigned int irq);
 
+domid_t irq_get_domain_id(struct irq_desc *desc);
+
 void arch_move_irqs(struct vcpu *v);
 
 #define arch_evtchn_bind_pirq(d, pirq) ((void)((d) + (pirq)))
-- 
2.9.2


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