[PATCH] x86: irq_comm: Add check for RH bit in kvm_set_msi_irq

[James Sullivan <sullivan.james.f@gmail.com>]

Hi folks,

This is a small patch that implements logic to handle the RH bit
being set in the msi message address register. Currently the DM bit is
the only thing used to decide irq->dest_mode (logical when DM set,
physical when unset). Documentation indicates that the DM bit will be
ignored when the RH bit is unset, and physical destination mode is used
in this case.

Fixed this to set irq->dest_mode to logical just when both bits are set,
and physical otherwise.

Signed-off-by: James Sullivan <sullivan.james.f@gmail.com>
---
 arch/x86/kvm/irq_comm.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index 72298b3..26bbab8 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -97,18 +97,26 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
 static inline void kvm_set_msi_irq(struct kvm_kernel_irq_routing_entry *e,
 				   struct kvm_lapic_irq *irq)
 {
+	bool phys;
 	trace_kvm_msi_set_irq(e->msi.address_lo, e->msi.data);

 	irq->dest_id = (e->msi.address_lo &
 			MSI_ADDR_DEST_ID_MASK) >> MSI_ADDR_DEST_ID_SHIFT;
 	irq->vector = (e->msi.data &
 			MSI_DATA_VECTOR_MASK) >> MSI_DATA_VECTOR_SHIFT;
-	irq->dest_mode = (1 << MSI_ADDR_DEST_MODE_SHIFT) & e->msi.address_lo;
+	/*
+	 * Set dest_mode to logical just in case both the RH and DM
+	 * bits are set, otherwise default to physical.
+	 */
+	phys = ((e->msi.address_lo & (MSI_ADDR_REDIRECTION_LOWPRI |
+			MSI_ADDR_DEST_MODE_LOGICAL)) !=
+		(MSI_ADDR_REDIRECTION_LOWPRI |
+			MSI_ADDR_DEST_MODE_LOGICAL));
+	irq->dest_mode = phys ? 0 : (MSI_ADDR_DEST_MODE_LOGICAL);
 	irq->trig_mode = (1 << MSI_DATA_TRIGGER_SHIFT) & e->msi.data;
 	irq->delivery_mode = e->msi.data & 0x700;
 	irq->level = 1;
 	irq->shorthand = 0;
-	/* TODO Deal with RH bit of MSI message address */
 }

 int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
-- 
2.3.1