[PATCH] RISC-V: KVM: Preserve LCOFIP when checking pending interrupts

[Pengpeng Hou]

KVM injects the guest counter-overflow interrupt into HVIP bit 13 and
records the same bit in irqs_pending. The guest enables it through VSIE
LCOFIE, also at bit 13.

kvm_riscv_vcpu_has_interrupts() shifts the complete VSIP valid mask by
VSIP_TO_HVIP_SHIFT before matching it against irqs_pending. That maps
SSIP, STIP, and SEIP to VSSIP, VSTIP, and VSEIP, but incorrectly moves
LCOFIP from bit 13 to bit 14. The following high-interrupt term excludes
all local interrupt bits, so it cannot recover LCOFIP.

As a result, kvm_arch_vcpu_runnable() can report false for a vCPU waiting
in WFI even though an enabled PMU overflow interrupt is pending.

Keep LCOFIP in place while shifting the three interrupt classes that have
distinct VS-level bit positions. This makes a vCPU halted in WFI runnable
when its PMU overflow interrupt is pending.

Fixes: 16b0bde9a37c ("RISC-V: KVM: Add perf sampling support for guests")
Signed-off-by: Pengpeng Hou <pengpeng at iscas.ac.cn>
---
 arch/riscv/kvm/vcpu.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index e062ca1..c6eb3bd 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -487,12 +487,14 @@ int kvm_riscv_vcpu_unset_interrupt(struct kvm_vcpu *vcpu, unsigned int irq)
 bool kvm_riscv_vcpu_has_interrupts(struct kvm_vcpu *vcpu, u64 mask)
 {
 	unsigned long flags;
-	unsigned long ie;
+	unsigned long ie, vsie;
 	bool ret;
 
 	raw_spin_lock_irqsave(&vcpu->arch.irqs_pending_lock, flags);
-	ie = ((vcpu->arch.guest_csr.vsie & VSIP_VALID_MASK)
-		<< VSIP_TO_HVIP_SHIFT) & (unsigned long)mask;
+	vsie = vcpu->arch.guest_csr.vsie & VSIP_VALID_MASK;
+	ie = ((vsie & ~SIP_LCOFIP) << VSIP_TO_HVIP_SHIFT) |
+	     (vsie & SIP_LCOFIP);
+	ie &= (unsigned long)mask;
 	ie |= vcpu->arch.guest_csr.vsie & ~IRQ_LOCAL_MASK &
 		(unsigned long)mask;
 	ret = vcpu->arch.irqs_pending[0] & ie;