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Re: [Xen-devel] [PATCH 38/57] ARM: new VGIC: Add PENDING registers handlers
Hi Andre,
On 03/05/2018 04:03 PM, Andre Przywara wrote:
The pending 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.
For level triggered interrupts the real line level is unaffected by
this write, so we keep this state separate and combine it with the
device's level to get the actual pending state.
Hardware mapped IRQs need some special handling, as their hardware state
has to be coordinated with the virtual pending bit to avoid hanging
or masked interrupts.
This is based on Linux commit 96b298000db4, written by Andre Przywara.
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
---
Changelog RFC ... v1:
- propagate SET/CLEAR_PENDING requests to hardware
xen/arch/arm/vgic/vgic-mmio-v2.c | 4 +-
xen/arch/arm/vgic/vgic-mmio.c | 125 +++++++++++++++++++++++++++++++++++++++
xen/arch/arm/vgic/vgic-mmio.h | 11 ++++
3 files changed, 138 insertions(+), 2 deletions(-)
diff --git a/xen/arch/arm/vgic/vgic-mmio-v2.c b/xen/arch/arm/vgic/vgic-mmio-v2.c
index 3dd983f885..efdd73301d 100644
--- a/xen/arch/arm/vgic/vgic-mmio-v2.c
+++ b/xen/arch/arm/vgic/vgic-mmio-v2.c
@@ -86,10 +86,10 @@ static const struct vgic_register_region
vgic_v2_dist_registers[] = {
vgic_mmio_read_enable, vgic_mmio_write_cenable, 1,
VGIC_ACCESS_32bit),
REGISTER_DESC_WITH_BITS_PER_IRQ(GICD_ISPENDR,
- vgic_mmio_read_raz, vgic_mmio_write_wi, 1,
+ vgic_mmio_read_pending, vgic_mmio_write_spending, 1,
VGIC_ACCESS_32bit),
REGISTER_DESC_WITH_BITS_PER_IRQ(GICD_ICPENDR,
- vgic_mmio_read_raz, vgic_mmio_write_wi, 1,
+ vgic_mmio_read_pending, vgic_mmio_write_cpending, 1,
VGIC_ACCESS_32bit),
REGISTER_DESC_WITH_BITS_PER_IRQ(GICD_ISACTIVER,
vgic_mmio_read_raz, vgic_mmio_write_wi, 1,
diff --git a/xen/arch/arm/vgic/vgic-mmio.c b/xen/arch/arm/vgic/vgic-mmio.c
index f8f0252eff..2e939d5e39 100644
--- a/xen/arch/arm/vgic/vgic-mmio.c
+++ b/xen/arch/arm/vgic/vgic-mmio.c
@@ -156,6 +156,131 @@ void vgic_mmio_write_cenable(struct vcpu *vcpu,
}
}
+unsigned long vgic_mmio_read_pending(struct vcpu *vcpu,
+ paddr_t addr, unsigned int len)
+{
+ uint32_t intid = VGIC_ADDR_TO_INTID(addr, 1);
+ uint32_t value = 0;
+ unsigned int i;
+
+ /* Loop over all IRQs affected by this read */
+ for ( i = 0; i < len * 8; i++ )
+ {
+ struct vgic_irq *irq = vgic_get_irq(vcpu->domain, vcpu, intid + i);
+
+ if ( irq_is_pending(irq) )
+ value |= (1U << i);
+
+ vgic_put_irq(vcpu->domain, irq);
+ }
+
+ return value;
+}
+
+void vgic_mmio_write_spending(struct vcpu *vcpu,
+ paddr_t addr, unsigned int len,
+ unsigned long val)
+{
+ uint32_t intid = VGIC_ADDR_TO_INTID(addr, 1);
+ unsigned int i;
+ unsigned long flags;
+ irq_desc_t *desc;
+
+ for_each_set_bit( i, &val, len * 8 )
+ {
+ struct vgic_irq *irq = vgic_get_irq(vcpu->domain, vcpu, intid + i);
+
+ spin_lock_irqsave(&irq->irq_lock, flags);
+ irq->pending_latch = true;
+
+ /* To observe the locking order, just take the irq_desc pointer here.
*/
+ if ( irq->hw )
+ desc = irq_to_desc(irq->hwintid);
+ else
+ desc = NULL;
+
+ vgic_queue_irq_unlock(vcpu->domain, irq, flags);
+
+ /*
+ * When the VM sets the pending state for a HW interrupt on the virtual
+ * distributor we set the active state on the physical distributor,
+ * because the virtual interrupt can become active and then the guest
+ * can deactivate it.
+ */
+ if ( desc )
+ {
+ spin_lock_irqsave(&desc->lock, flags);
+ spin_lock(&irq->irq_lock);
+
+ /* Is this h/w IRQ still assigned to the virtual IRQ? */
Same remark as for the enable in patch #37. What if the h/w IRQ has changed?
I am trying to think in potential use case where a physical interrupt
would be removed from a domain. The only one I can think is a interrupt
routed back to the hardware domain after a guest is destroyed.
But I am not entirely convinced this would work correctly today. Mostly
because we don't sync the vIRQ state back to the pIRQ state (e.g enable,
pending, active) in vgic_connect_hw_irq.
This could lead to interesting issue depending on the vIRQ state. So may
we should just enforce that a physical interrupt is routed to a domain
for its full life. Any opinions?
+ if ( irq->hw && desc->irq == irq->hwintid )
+ gic_set_active_state(desc, true);
+
+ spin_unlock(&irq->irq_lock);
+ spin_unlock_irqrestore(&desc->lock, flags);
+ }
+
+ vgic_put_irq(vcpu->domain, irq);
+ }
+}
+
+void vgic_mmio_write_cpending(struct vcpu *vcpu,
+ paddr_t addr, unsigned int len,
+ unsigned long val)
+{
+ uint32_t intid = VGIC_ADDR_TO_INTID(addr, 1);
+ unsigned int i;
+ unsigned long flags;
+ irq_desc_t *desc;
+
+ for_each_set_bit( i, &val, len * 8 )
+ {
+ struct vgic_irq *irq = vgic_get_irq(vcpu->domain, vcpu, intid + i);
+
+ spin_lock_irqsave(&irq->irq_lock, flags);
+ irq->pending_latch = false;
+
+ /* To observe the locking order, just take the irq_desc pointer here.
*/
+ if ( irq->hw )
+ desc = irq_to_desc(irq->hwintid);
+ else
+ desc = NULL;
+
+ spin_unlock_irqrestore(&irq->irq_lock, flags);
+
+ /*
+ * We don't want the guest to effectively mask the physical
+ * interrupt by doing a write to SPENDR followed by a write to
+ * CPENDR for HW interrupts, so we clear the active state on
+ * the physical side if the virtual interrupt is not active.
+ * This may lead to taking an additional interrupt on the
+ * host, but that should not be a problem as the worst that
+ * can happen is an additional vgic injection. We also clear
+ * the pending state to maintain proper semantics for edge HW
+ * interrupts.
+ */
+ if ( desc )
+ {
+ spin_lock_irqsave(&desc->lock, flags);
+ spin_lock(&irq->irq_lock);
+
+ /* Is this h/w IRQ still assigned to the virtual IRQ? */
+ if ( irq->hw && desc->irq == irq->hwintid )
+ {
+ gic_set_pending_state(desc, false);
+ if (!irq->active)
+ gic_set_active_state(desc, false);
+ }
+
+ spin_unlock(&irq->irq_lock);
+ spin_unlock_irqrestore(&desc->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 2ddcbbf58d..4465f3b7e5 100644
--- a/xen/arch/arm/vgic/vgic-mmio.h
+++ b/xen/arch/arm/vgic/vgic-mmio.h
@@ -107,6 +107,17 @@ void vgic_mmio_write_cenable(struct vcpu *vcpu,
paddr_t addr, unsigned int len,
unsigned long val);
+unsigned long vgic_mmio_read_pending(struct vcpu *vcpu,
+ paddr_t addr, unsigned int len);
+
+void vgic_mmio_write_spending(struct vcpu *vcpu,
+ paddr_t addr, unsigned int len,
+ unsigned long val);
+
+void vgic_mmio_write_cpending(struct vcpu *vcpu,
+ paddr_t addr, unsigned int len,
+ unsigned long val);
+
unsigned int vgic_v2_init_dist_iodev(struct vgic_io_device *dev);
#endif
Cheers,
--
Julien Grall
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