arm/arm64: KVM: Allow a VCPU to fully reset itself

The current kvm_psci_vcpu_on implementation will directly try to
manipulate the state of the VCPU to reset it.  However, since this is
not done on the thread that runs the VCPU, we can end up in a strangely
corrupted state when the source and target VCPUs are running at the same
time.

Fix this by factoring out all reset logic from the PSCI implementation
and forwarding the required information along with a request to the
target VCPU.

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/arch/arm/kvm/reset.c b/arch/arm/kvm/reset.c
index 5ed0c3ee33d6..e53327912adc 100644
--- a/arch/arm/kvm/reset.c
+++ b/arch/arm/kvm/reset.c
@@ -26,6 +26,7 @@
 #include <asm/cputype.h>
 #include <asm/kvm_arm.h>
 #include <asm/kvm_coproc.h>
+#include <asm/kvm_emulate.h>
 
 #include <kvm/arm_arch_timer.h>
 
@@ -69,6 +70,29 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 	/* Reset CP15 registers */
 	kvm_reset_coprocs(vcpu);
 
+	/*
+	 * Additional reset state handling that PSCI may have imposed on us.
+	 * Must be done after all the sys_reg reset.
+	 */
+	if (READ_ONCE(vcpu->arch.reset_state.reset)) {
+		unsigned long target_pc = vcpu->arch.reset_state.pc;
+
+		/* Gracefully handle Thumb2 entry point */
+		if (target_pc & 1) {
+			target_pc &= ~1UL;
+			vcpu_set_thumb(vcpu);
+		}
+
+		/* Propagate caller endianness */
+		if (vcpu->arch.reset_state.be)
+			kvm_vcpu_set_be(vcpu);
+
+		*vcpu_pc(vcpu) = target_pc;
+		vcpu_set_reg(vcpu, 0, vcpu->arch.reset_state.r0);
+
+		vcpu->arch.reset_state.reset = false;
+	}
+
 	/* Reset arch_timer context */
 	return kvm_timer_vcpu_reset(vcpu);
 }