[Xen-devel] [PATCH 23/57] ARM: GIC: allow reading pending state of a hardware IRQ

[Andre Przywara <andre.przywara@xxxxxxxxxx>]

To synchronize level triggered interrupts which are mapped into a guest,
we need to update the virtual line level at certain points in time.
For a hardware mapped interrupt the GIC is the only place where we can
easily access this information.
Implement a gic_hw_operations member to return the pending state of a
particular interrupt. Due to hardware limitations this only works for
private interrupts of the current CPU, so there is no CPU field in the
prototype.
This adds gicv2/3_peek_irq() helper functions, to read a bit in a bitmap
spread over several MMIO registers.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
---
Changelog RFC ... v1:
- add gicv2/3_peek_irq() helpers
- use struct irq_desc* in the interface (instead of just the IRQ number)

 xen/arch/arm/gic-v2.c     | 15 +++++++++++++++
 xen/arch/arm/gic-v3.c     | 19 +++++++++++++++++++
 xen/arch/arm/gic.c        |  5 +++++
 xen/include/asm-arm/gic.h |  5 +++++
 4 files changed, 44 insertions(+)

diff --git a/xen/arch/arm/gic-v2.c b/xen/arch/arm/gic-v2.c
index 74169b5633..48352f6499 100644
--- a/xen/arch/arm/gic-v2.c
+++ b/xen/arch/arm/gic-v2.c
@@ -241,6 +241,15 @@ static void gicv2_poke_irq(struct irq_desc *irqd, uint32_t 
offset)
     writel_gicd(1U << (irqd->irq % 32), offset + (irqd->irq / 32) * 4);
 }
 
+static bool gicv2_peek_irq(struct irq_desc *irqd, uint32_t offset)
+{
+    uint32_t reg;
+
+    reg = readl_gicd(offset + (irqd->irq / 32) * 4) & (1U << (irqd->irq % 32));
+
+    return reg;
+}
+
 static void gicv2_set_active_state(struct irq_desc *irqd, bool active)
 {
     ASSERT(spin_is_locked(&irqd->lock));
@@ -549,6 +558,11 @@ static unsigned int gicv2_read_apr(int apr_reg)
    return readl_gich(GICH_APR);
 }
 
+static bool gicv2_read_pending_state(struct irq_desc *irqd)
+{
+    return gicv2_peek_irq(irqd, GICD_ISPENDR);
+}
+
 static void gicv2_irq_enable(struct irq_desc *desc)
 {
     unsigned long flags;
@@ -1294,6 +1308,7 @@ const static struct gic_hw_operations gicv2_ops = {
     .write_lr            = gicv2_write_lr,
     .read_vmcr_priority  = gicv2_read_vmcr_priority,
     .read_apr            = gicv2_read_apr,
+    .read_pending_state  = gicv2_read_pending_state,
     .make_hwdom_dt_node  = gicv2_make_hwdom_dt_node,
     .make_hwdom_madt     = gicv2_make_hwdom_madt,
     .get_hwdom_extra_madt_size = gicv2_get_hwdom_extra_madt_size,
diff --git a/xen/arch/arm/gic-v3.c b/xen/arch/arm/gic-v3.c
index c96469f09d..3e75d06c3b 100644
--- a/xen/arch/arm/gic-v3.c
+++ b/xen/arch/arm/gic-v3.c
@@ -444,6 +444,19 @@ static void gicv3_poke_irq(struct irq_desc *irqd, u32 
offset, bool wait_for_rwp)
         gicv3_wait_for_rwp(irqd->irq);
 }
 
+static bool gicv3_peek_irq(struct irq_desc *irqd, u32 offset)
+{
+    void __iomem *base;
+    unsigned int irq = irqd->irq;
+
+    if ( irq >= NR_GIC_LOCAL_IRQS)
+        base = GICD + (irq / 32) * 4;
+    else
+        base = GICD_RDIST_SGI_BASE;
+
+    return !!(readl(base + offset) & (1U << (irq % 32)));
+}
+
 static void gicv3_unmask_irq(struct irq_desc *irqd)
 {
     gicv3_poke_irq(irqd, GICD_ISENABLER, false);
@@ -1094,6 +1107,11 @@ static unsigned int gicv3_read_apr(int apr_reg)
     }
 }
 
+static bool gicv3_read_pending_state(struct irq_desc *irqd)
+{
+    return gicv3_peek_irq(irqd, GICD_ISPENDR);
+}
+
 static void gicv3_irq_enable(struct irq_desc *desc)
 {
     unsigned long flags;
@@ -1762,6 +1780,7 @@ static const struct gic_hw_operations gicv3_ops = {
     .write_lr            = gicv3_write_lr,
     .read_vmcr_priority  = gicv3_read_vmcr_priority,
     .read_apr            = gicv3_read_apr,
+    .read_pending_state  = gicv3_read_pending_state,
     .secondary_init      = gicv3_secondary_cpu_init,
     .make_hwdom_dt_node  = gicv3_make_hwdom_dt_node,
     .make_hwdom_madt     = gicv3_make_hwdom_madt,
diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index f1329a630a..67c3b4d86d 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -116,6 +116,11 @@ static void gic_set_irq_priority(struct irq_desc *desc, 
unsigned int priority)
     gic_hw_ops->set_irq_priority(desc, priority);
 }
 
+bool gic_read_pending_state(struct irq_desc *irqd)
+{
+    return gic_hw_ops->read_pending_state(irqd);
+}
+
 /* Program the GIC to route an interrupt to the host (i.e. Xen)
  * - needs to be called with desc.lock held
  */
diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
index 46dcb0fe7c..03667f00cf 100644
--- a/xen/include/asm-arm/gic.h
+++ b/xen/include/asm-arm/gic.h
@@ -248,6 +248,9 @@ void gic_set_pending_state(struct irq_desc *irqd, bool 
state);
 /* Program the IRQ type into the GIC */
 void gic_set_irq_type(struct irq_desc *desc, unsigned int type);
 
+/* Read the pending state of an interrupt from the distributor. */
+bool gic_read_pending_state(struct irq_desc *irqd);
+
 /* 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,
@@ -382,6 +385,8 @@ struct gic_hw_operations {
     unsigned int (*read_vmcr_priority)(void);
     /* Read APRn register */
     unsigned int (*read_apr)(int apr_reg);
+    /* Query the pending state of an interrupt at the distributor level. */
+    bool (*read_pending_state)(struct irq_desc *irqd);
     /* Secondary CPU init */
     int (*secondary_init)(void);
     /* Create GIC node for the hardware domain */
-- 
2.14.1


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