[Xen-devel] [PATCH v2 7/9] xen/arm: Allow DOM0 to set the IRQ type

[Julien Grall <julien.grall@xxxxxxx>]

The function route_irq_to_guest mandates the IRQ type, stored in
desc->arch.type, to be valid. However, in case of ACPI, these
information is not part of the static tables. Therefore Xen needs to
rely on DOM0 to provide a valid type based on the firmware tables.

A new helper, irq_type_set_by_domain is provided to check whether a
domain is allowed to set the IRQ type. For now, only DOM0 is allowed to
configure.

When the helper returns 1, the routing function will not check whether
the IRQ type is correctly set and configure the GIC. Instead, this will
be done when the domain will enable the interrupt.

Note that irq_set_spi_type is not called because it validates the type
and does not allow it the domain to change the type after the first
write. It means that desc->arch.type may never be set, which is fine
because the field is only used to configure the type during the routing.

Based on 4.3.13 in ARM IHI 0048B.b, changing the value of Int_config is
UNPREDICTABLE when the corresponding interrupt is not disabled.

Therefore, setting the IRQ type when the guest is writing into ICFGR
would require more work to make sure the IRQ has been disabled before
writing into the host ICFGR. As the behavior is UNPREDICTABLE, the type
will be set before enabling the physical IRQ associated to the virtual IRQ.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

---

It might be possible to let any domain configure the IRQ
type (could be useful when passthrough an IRQ with ACPI). However, we would
need to consider any potential security impact beforehand.

    Changes in v2:
        - Rename the patch
        - Allow any DOM0 to set the IRQ type
        - Re-use in part of vgic_get_virq_type from
        "Configure SPI interrupt type and route to Dom0 dynamically".
        - Add rationale why the IRQ type is set in enable
---
 xen/arch/arm/gic.c        |  5 +++--
 xen/arch/arm/irq.c        | 13 ++++++++++++-
 xen/arch/arm/vgic.c       | 19 +++++++++++++++++++
 xen/include/asm-arm/gic.h |  3 +++
 xen/include/asm-arm/irq.h |  6 ++++++
 5 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 72bb885..63c744a 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -97,7 +97,7 @@ void gic_restore_state(struct vcpu *v)
 }
 
 /* desc->irq needs to be disabled before calling this function */
-static void gic_set_irq_type(struct irq_desc *desc, unsigned int type)
+void gic_set_irq_type(struct irq_desc *desc, unsigned int type)
 {
     /*
      * IRQ must be disabled before configuring it (see 4.3.13 in ARM IHI
@@ -160,7 +160,8 @@ int gic_route_irq_to_guest(struct domain *d, unsigned int 
virq,
     desc->handler = gic_hw_ops->gic_guest_irq_type;
     set_bit(_IRQ_GUEST, &desc->status);
 
-    gic_set_irq_type(desc, desc->arch.type);
+    if ( !irq_type_set_by_domain(d) )
+        gic_set_irq_type(desc, desc->arch.type);
     gic_set_irq_priority(desc, priority);
 
     p->desc = desc;
diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
index 3fc22f2..06d4843 100644
--- a/xen/arch/arm/irq.c
+++ b/xen/arch/arm/irq.c
@@ -395,6 +395,17 @@ bool_t is_assignable_irq(unsigned int irq)
 }
 
 /*
+ * Only the hardware domain is allowed to set the configure the
+ * interrupt type for now.
+ *
+ * XXX: See whether it is possible to let any domain configure the type.
+ */
+bool_t irq_type_set_by_domain(const struct domain *d)
+{
+    return (d == hardware_domain);
+}
+
+/*
  * Route an IRQ to a specific guest.
  * For now only SPIs are assignable to the guest.
  */
@@ -449,7 +460,7 @@ int route_irq_to_guest(struct domain *d, unsigned int virq,
 
     spin_lock_irqsave(&desc->lock, flags);
 
-    if ( desc->arch.type == IRQ_TYPE_INVALID )
+    if ( !irq_type_set_by_domain(d) && desc->arch.type == IRQ_TYPE_INVALID )
     {
         printk(XENLOG_G_ERR "IRQ %u has not been configured\n", irq);
         retval = -EIO;
diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index 5070452..a7ccfe7 100644
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -344,6 +344,22 @@ void vgic_disable_irqs(struct vcpu *v, uint32_t r, int n)
     }
 }
 
+#define VGIC_ICFG_MASK(intr) (1 << ((2 * ((intr) % 16)) + 1))
+
+/* The function should be called with the rank lock taken */
+static inline unsigned int vgic_get_virq_type(struct vcpu *v, int n, int index)
+{
+    struct vgic_irq_rank *r = vgic_get_rank(v, n);
+    uint32_t tr = r->icfg[index >> 4];
+
+    ASSERT(spin_is_locked(&r->lock));
+
+    if ( tr & VGIC_ICFG_MASK(index) )
+        return IRQ_TYPE_EDGE_RISING;
+    else
+        return IRQ_TYPE_LEVEL_HIGH;
+}
+
 void vgic_enable_irqs(struct vcpu *v, uint32_t r, int n)
 {
     const unsigned long mask = r;
@@ -352,6 +368,7 @@ void vgic_enable_irqs(struct vcpu *v, uint32_t r, int n)
     unsigned long flags;
     int i = 0;
     struct vcpu *v_target;
+    struct domain *d = v->domain;
 
     while ( (i = find_next_bit(&mask, 32, i)) < 32 ) {
         irq = i + (32 * n);
@@ -366,6 +383,8 @@ void vgic_enable_irqs(struct vcpu *v, uint32_t r, int n)
         {
             irq_set_affinity(p->desc, cpumask_of(v_target->processor));
             spin_lock_irqsave(&p->desc->lock, flags);
+            if ( irq_type_set_by_domain(d) )
+                gic_set_irq_type(p->desc, vgic_get_virq_type(v, n, i));
             p->desc->handler->enable(p->desc);
             spin_unlock_irqrestore(&p->desc->lock, flags);
         }
diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
index 2214e87..836a103 100644
--- a/xen/include/asm-arm/gic.h
+++ b/xen/include/asm-arm/gic.h
@@ -222,6 +222,9 @@ enum gic_version {
 
 extern enum gic_version gic_hw_version(void);
 
+/* Program the IRQ type into the GIC */
+void gic_set_irq_type(struct irq_desc *desc, unsigned int type);
+
 /* Program the GIC to route an interrupt */
 extern void gic_route_irq_to_xen(struct irq_desc *desc, unsigned int priority);
 extern int gic_route_irq_to_guest(struct domain *, unsigned int virq,
diff --git a/xen/include/asm-arm/irq.h b/xen/include/asm-arm/irq.h
index 493773c..8f7a167 100644
--- a/xen/include/asm-arm/irq.h
+++ b/xen/include/asm-arm/irq.h
@@ -58,6 +58,12 @@ int platform_get_irq(const struct dt_device_node *device, 
int index);
 
 void irq_set_affinity(struct irq_desc *desc, const cpumask_t *cpu_mask);
 
+/*
+ * Use this helper in places that need to know whether the IRQ type is
+ * set by the domain.
+ */
+bool_t irq_type_set_by_domain(const struct domain *d);
+
 #endif /* _ASM_HW_IRQ_H */
 /*
  * Local variables:
-- 
1.9.1


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