KVM: arm64: Don't miss pending interrupts for suspended vCPU

In order to properly emulate the WFI instruction, KVM reads back
ICH_VMCR_EL2 and enables doorbells for GICv4. These preparations are
necessary in order to recognize pending interrupts in
kvm_arch_vcpu_runnable() and return to the guest. Until recently, this
work was done by kvm_arch_vcpu_{blocking,unblocking}(). Since commit
6109c5a6ab7f ("KVM: arm64: Move vGIC v4 handling for WFI out arch
callback hook"), these callbacks were gutted and superseded by
kvm_vcpu_wfi().

It is important to note that KVM implements PSCI CPU_SUSPEND calls as
a WFI within the guest. However, the implementation calls directly into
kvm_vcpu_halt(), which skips the needed work done in kvm_vcpu_wfi()
to detect pending interrupts. Fix the issue by calling the WFI helper.

Fixes: 6109c5a6ab7f ("KVM: arm64: Move vGIC v4 handling for WFI out arch callback hook")
Signed-off-by: Oliver Upton <oupton@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220217101242.3013716-1-oupton@google.com

diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index 3eae328..2ce60fe 100644 (file)
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -46,8 +46,7 @@ static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
         * specification (ARM DEN 0022A). This means all suspend states
         * for KVM will preserve the register state.
         */
-       kvm_vcpu_halt(vcpu);
-       kvm_clear_request(KVM_REQ_UNHALT, vcpu);
+       kvm_vcpu_wfi(vcpu);
 
        return PSCI_RET_SUCCESS;
 }