[Xen-devel] [RFC PATCH 33/49] ARM: new VGIC: Add PRIORITY registers handlers

[Andre Przywara <andre.przywara@xxxxxxxxxx>]

The priority register handlers are shared between the v2 and v3 emulation,
so their implementation goes into vgic-mmio.c, to be easily referenced
from the v3 emulation as well later.
There is a corner case when we change the priority of a pending
interrupt which we don't handle at the moment.

This is based on Linux commit dd238ec2b87b, written by Andre Przywara.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
---
 xen/arch/arm/vgic/vgic-mmio-v2.c |  4 ++--
 xen/arch/arm/vgic/vgic-mmio.c    | 47 ++++++++++++++++++++++++++++++++++++++++
 xen/arch/arm/vgic/vgic-mmio.h    |  7 ++++++
 xen/arch/arm/vgic/vgic.h         |  2 ++
 4 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/vgic/vgic-mmio-v2.c b/xen/arch/arm/vgic/vgic-mmio-v2.c
index eba24d9866..0574ff9b16 100644
--- a/xen/arch/arm/vgic/vgic-mmio-v2.c
+++ b/xen/arch/arm/vgic/vgic-mmio-v2.c
@@ -92,8 +92,8 @@ static const struct vgic_register_region 
vgic_v2_dist_registers[] = {
         vgic_mmio_read_active, vgic_mmio_write_cactive, NULL, NULL, 1,
         VGIC_ACCESS_32bit),
     REGISTER_DESC_WITH_BITS_PER_IRQ(GICD_IPRIORITYR,
-        vgic_mmio_read_raz, vgic_mmio_write_wi, NULL, NULL, 8,
-        VGIC_ACCESS_32bit | VGIC_ACCESS_8bit),
+        vgic_mmio_read_priority, vgic_mmio_write_priority, NULL, NULL,
+        8, VGIC_ACCESS_32bit | VGIC_ACCESS_8bit),
     REGISTER_DESC_WITH_BITS_PER_IRQ(GICD_ITARGETSR,
         vgic_mmio_read_raz, vgic_mmio_write_wi, NULL, NULL, 8,
         VGIC_ACCESS_32bit | VGIC_ACCESS_8bit),
diff --git a/xen/arch/arm/vgic/vgic-mmio.c b/xen/arch/arm/vgic/vgic-mmio.c
index ac3aa03fbc..14570d9d8e 100644
--- a/xen/arch/arm/vgic/vgic-mmio.c
+++ b/xen/arch/arm/vgic/vgic-mmio.c
@@ -309,6 +309,53 @@ void vgic_mmio_write_sactive(struct vcpu *vcpu,
     spin_unlock(&vcpu->domain->domain_lock);
 }
 
+unsigned long vgic_mmio_read_priority(struct vcpu *vcpu,
+                      paddr_t addr, unsigned int len)
+{
+    u32 intid = VGIC_ADDR_TO_INTID(addr, 8);
+    int i;
+    u64 val = 0;
+
+    for ( i = 0; i < len; i++ )
+    {
+        struct vgic_irq *irq = vgic_get_irq(vcpu->domain, vcpu, intid + i);
+
+        val |= (u64)irq->priority << (i * 8);
+
+        vgic_put_irq(vcpu->domain, irq);
+    }
+
+    return val;
+}
+
+/*
+ * We currently don't handle changing the priority of an interrupt that
+ * is already pending on a VCPU. If there is a need for this, we would
+ * need to make this VCPU exit and re-evaluate the priorities, potentially
+ * leading to this interrupt getting presented now to the guest (if it has
+ * been masked by the priority mask before).
+ */
+void vgic_mmio_write_priority(struct vcpu *vcpu,
+                  paddr_t addr, unsigned int len,
+                  unsigned long val)
+{
+    u32 intid = VGIC_ADDR_TO_INTID(addr, 8);
+    int i;
+    unsigned long flags;
+
+    for ( i = 0; i < len; i++ )
+    {
+        struct vgic_irq *irq = vgic_get_irq(vcpu->domain, vcpu, intid + i);
+
+        spin_lock_irqsave(&irq->irq_lock, flags);
+        /* Narrow the priority range to what we actually support */
+        irq->priority = (val >> (i * 8)) & GENMASK(7, 8 - VGIC_PRI_BITS);
+        spin_unlock_irqrestore(&irq->irq_lock, flags);
+
+        vgic_put_irq(vcpu->domain, irq);
+    }
+}
+
 static int match_region(const void *key, const void *elt)
 {
     const unsigned int offset = (unsigned long)key;
diff --git a/xen/arch/arm/vgic/vgic-mmio.h b/xen/arch/arm/vgic/vgic-mmio.h
index 39e854232e..30221096b9 100644
--- a/xen/arch/arm/vgic/vgic-mmio.h
+++ b/xen/arch/arm/vgic/vgic-mmio.h
@@ -170,6 +170,13 @@ void vgic_mmio_write_sactive(struct vcpu *vcpu,
                  paddr_t addr, unsigned int len,
                  unsigned long val);
 
+unsigned long vgic_mmio_read_priority(struct vcpu *vcpu,
+                      paddr_t addr, unsigned int len);
+
+void vgic_mmio_write_priority(struct vcpu *vcpu,
+                  paddr_t addr, unsigned int len,
+                  unsigned long val);
+
 unsigned int vgic_v2_init_dist_iodev(struct vgic_io_device *dev);
 
 /* Find the proper register handler entry given a certain address offset */
diff --git a/xen/arch/arm/vgic/vgic.h b/xen/arch/arm/vgic/vgic.h
index 82fe902e26..b104f8e964 100644
--- a/xen/arch/arm/vgic/vgic.h
+++ b/xen/arch/arm/vgic/vgic.h
@@ -20,6 +20,8 @@
 #define PRODUCT_ID_KVM      0x4b    /* ASCII code K */
 #define IMPLEMENTER_ARM     0x43b
 
+#define VGIC_PRI_BITS       5
+
 #define vgic_irq_is_sgi(intid) ((intid) < VGIC_NR_SGIS)
 
 static inline bool irq_is_pending(struct vgic_irq *irq)
-- 
2.14.1


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel