[Xen-devel,RFC,7/8] xen/arm: Allow DOM0 to set the irq type when ACPI is inuse

Message ID 1465318123-3090-8-git-send-email-julien.grall@arm.com
State New
Headers show

Commit Message

Julien Grall June 7, 2016, 4:48 p.m.
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 it when ACPI is inuse.

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 will never be set, which is fine
because the field is only used to configure the type during the routing.

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

---

I am thinking to at least extend the behavior to DOM0 using DT. This
would make us resilient to a DT not providing the correct type without
having to workaround them in Xen.

Furthermore, it might be possible to let any domain configuring the IRQ
type (could be useful when passthrough an IRQ with ACPI). However, we would
need to consider any potential security impact beforehand.
---
 xen/arch/arm/gic.c        |  5 +++--
 xen/arch/arm/irq.c        | 14 +++++++++++++-
 xen/arch/arm/vgic.c       | 21 +++++++++++++++++++++
 xen/include/asm-arm/gic.h |  3 +++
 xen/include/asm-arm/irq.h |  6 ++++++
 5 files changed, 46 insertions(+), 3 deletions(-)

Comments

Julien Grall June 22, 2016, 11:46 a.m. | #1
Hi Stefano,

On 22/06/16 12:23, Stefano Stabellini wrote:
> On Tue, 7 Jun 2016, Julien Grall wrote:
>> 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 it when ACPI is inuse.
>>
>> 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 will never be set, which is fine
>> because the field is only used to configure the type during the routing.
>>
>> Signed-off-by: Julien Grall <julien.grall@arm.com>
>>
>> ---
>>
>> I am thinking to at least extend the behavior to DOM0 using DT. This
>> would make us resilient to a DT not providing the correct type without
>> having to workaround them in Xen.
>
> I agree with you. It is also better to have only one way of doing things
> rather than two.

I will update this patch to allow the hardware domain setting the IRQ type.

[...]

>> +#define NR_CFG_PER_ICFGR 16
>> +#define NR_BITS_PER_CFG (32U / NR_CFG_PER_ICFGR)
>> +
>> +/* The function should be called witht the rank lock taken. */
>                                        ^ with
>
>> +static int __vgic_get_virq_type(struct vcpu *v, unsigned int virq)
>> +{
>> +    struct vgic_irq_rank *rank = vgic_rank_irq(v, virq);
>> +    uint8_t index = virq & INTERRUPT_RANK_MASK;
>> +    uint32_t reg = rank->icfg[index / NR_CFG_PER_ICFGR];
>> +    uint8_t val;
>> +
>> +    ASSERT(spin_is_locked(&rank->lock));
>> +
>> +    val = reg >> ((index % NR_CFG_PER_ICFGR) * NR_BITS_PER_CFG);
>> +
>> +    return (val & 0x2) ? IRQ_TYPE_EDGE_RISING : IRQ_TYPE_LEVEL_HIGH;
>> +}
>
> I would stick to the function and definition we already had from "from
> Configure SPI interrupt type and route to Dom0 dynamically" by Shannon:

I found Shannon's function more difficult to understand. However the 
code is simpler, so I will use his function for the next version.

>    #define VGIC_ICFG_MASK(intr) (1 << ((2 * ((intr) % 16)) + 1))
>
>    static inline unsigned int get_the_irq_type(struct vcpu *v, int n, int index)
>    {
>        struct vgic_irq_rank *vr = vgic_get_rank(v, n);
>        uint32_t tr = vr->icfg[index >> 4];
>
>        if ( tr & VGIC_ICFG_MASK(index) )
>            return IRQ_TYPE_EDGE_BOTH;
>        else
>            return IRQ_TYPE_LEVEL_MASK;
>    }
>
>
>
>>   void vgic_migrate_irq(struct vcpu *old, struct vcpu *new, unsigned int irq)
>>   {
>>       unsigned long flags;
>> @@ -342,6 +360,7 @@ 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);
>> @@ -356,6 +375,8 @@ 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, irq));
>>               p->desc->handler->enable(p->desc);
>>               spin_unlock_irqrestore(&p->desc->lock, flags);
>>           }
>
> This is OK. But I am wondering if it wouldn't make sense to call
> gic_set_irq_type when the guest actually writes to the virtual icfg?

Hmmm it looks like that I forgot to explain in the commit message why I 
chose to call gic_set_irq_type here.

Changing the value of Int_config is UNPREDICTABLE when the corresponding
interrupt is not disabled (see 4.3.13 in ARM IHI 0048B.b).

So calling gic_set_irq_type when the guest actualy writes to the virtual 
cfg would require to disable the IRQ before hand.

Given that the behavior is UNPREDICTABLE, I chose to set the type before 
enabling the IRQ because the resulting code is simpler.

Regards,

Patch

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 27cd177..80d93a8 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
@@ -162,7 +162,8 @@  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 2f8af72..b9d7749 100644
--- a/xen/arch/arm/irq.c
+++ b/xen/arch/arm/irq.c
@@ -27,6 +27,7 @@ 
 
 #include <asm/gic.h>
 #include <asm/vgic.h>
+#include <asm/acpi.h>
 
 static unsigned int local_irqs_type[NR_LOCAL_IRQS];
 static DEFINE_SPINLOCK(local_irqs_type_lock);
@@ -395,6 +396,17 @@  bool_t is_assignable_irq(unsigned int irq)
 }
 
 /*
+ * When ACPI is inuse, only the hardware domain knows the interrupt
+ * type.
+ *
+ * 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) && !acpi_disabled);
+}
+
+/*
  * Route an IRQ to a specific guest.
  * For now only SPIs are assignable to the guest.
  */
@@ -449,7 +461,7 @@  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 ( desc->arch.type == IRQ_TYPE_INVALID && !irq_type_set_by_domain(d) )
     {
         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 ee35683..3e1c572 100644
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -249,6 +249,24 @@  static int vgic_get_virq_priority(struct vcpu *v, unsigned int virq)
     return priority;
 }
 
+#define NR_CFG_PER_ICFGR 16
+#define NR_BITS_PER_CFG (32U / NR_CFG_PER_ICFGR)
+
+/* The function should be called witht the rank lock taken. */
+static int __vgic_get_virq_type(struct vcpu *v, unsigned int virq)
+{
+    struct vgic_irq_rank *rank = vgic_rank_irq(v, virq);
+    uint8_t index = virq & INTERRUPT_RANK_MASK;
+    uint32_t reg = rank->icfg[index / NR_CFG_PER_ICFGR];
+    uint8_t val;
+
+    ASSERT(spin_is_locked(&rank->lock));
+
+    val = reg >> ((index % NR_CFG_PER_ICFGR) * NR_BITS_PER_CFG);
+
+    return (val & 0x2) ? IRQ_TYPE_EDGE_RISING : IRQ_TYPE_LEVEL_HIGH;
+}
+
 void vgic_migrate_irq(struct vcpu *old, struct vcpu *new, unsigned int irq)
 {
     unsigned long flags;
@@ -342,6 +360,7 @@  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);
@@ -356,6 +375,8 @@  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, irq));
             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 ddc45a8..44b9ef6 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, const cpumask_t *cpu_mask,
                                  unsigned int priority);
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: