[PATCH v7 14/17] KVM: Update Posted-Interrupts Descriptor when vCPU is preempted

[Feng Wu]

This patch updates the Posted-Interrupts Descriptor when vCPU
is preempted.

sched out:
- Set 'SN' to suppress furture non-urgent interrupts posted for
the vCPU.

sched in:
- Clear 'SN'
- Change NDST if vCPU is scheduled to a different CPU
- Set 'NV' to POSTED_INTR_VECTOR

Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
---
 arch/x86/kvm/vmx.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 234f720..9c87064 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -45,6 +45,7 @@
 #include <asm/debugreg.h>
 #include <asm/kexec.h>
 #include <asm/apic.h>
+#include <asm/irq_remapping.h>
 
 #include "trace.h"
 #include "pmu.h"
@@ -2001,10 +2002,60 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 		vmcs_writel(HOST_IA32_SYSENTER_ESP, sysenter_esp); /* 22.2.3 */
 		vmx->loaded_vmcs->cpu = cpu;
 	}
+
+	if (irq_remapping_cap(IRQ_POSTING_CAP)) {
+		struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
+		struct pi_desc old, new;
+		unsigned int dest;
+
+		do {
+			old.control = new.control = pi_desc->control;
+
+			/*
+			 * If 'nv' field is POSTED_INTR_WAKEUP_VECTOR, there
+			 * are two possible cases:
+			 * 1. After running 'pi_pre_block', context switch
+			 *    happened. For this case, 'sn' was set in
+			 *    vmx_vcpu_put(), so we need to clear it here.
+			 * 2. After running 'pi_pre_block', we were blocked,
+			 *    and woken up by some other guy. For this case,
+			 *    we don't need to do anything, 'pi_post_block'
+			 *    will do everything for us. However, we cannot
+			 *    check whether it is case #1 or case #2 here
+			 *    (maybe, not needed), so we also clear sn here,
+			 *    I think it is not a big deal.
+			 */
+			if (pi_desc->nv != POSTED_INTR_WAKEUP_VECTOR) {
+				if (vcpu->cpu != cpu) {
+					dest = cpu_physical_id(cpu);
+
+					if (x2apic_enabled())
+						new.ndst = dest;
+					else
+						new.ndst = (dest << 8) & 0xFF00;
+				}
+
+				/* set 'NV' to 'notification vector' */
+				new.nv = POSTED_INTR_VECTOR;
+			}
+
+			/* Allow posting non-urgent interrupts */
+			new.sn = 0;
+		} while (cmpxchg(&pi_desc->control, old.control,
+				new.control) != old.control);
+	}
 }
 
 static void vmx_vcpu_put(struct kvm_vcpu *vcpu)
 {
+	if (irq_remapping_cap(IRQ_POSTING_CAP)) {
+		struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
+
+		/* Set SN when the vCPU is preempted */
+		if (vcpu->preempted)
+			pi_set_sn(pi_desc);
+	}
+
 	__vmx_load_host_state(to_vmx(vcpu));
 	if (!vmm_exclusive) {
 		__loaded_vmcs_clear(to_vmx(vcpu)->loaded_vmcs);
-- 
2.1.0

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