arm64: KVM: Make PSCI_VERSION a fast path

From: Marc Zyngier <marc.zyngier@arm.com>

commit 90348689d500410ca7a55624c667f956771dce7f upstream.

For those CPUs that require PSCI to perform a BP invalidation,
going all the way to the PSCI code for not much is a waste of
precious cycles. Let's terminate that call as early as possible.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com> [v4.9 backport]
Tested-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 5640f1d..b63a528 100644 (file)
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -17,6 +17,7 @@
 
 #include <linux/types.h>
 #include <linux/jump_label.h>
+#include <uapi/linux/psci.h>
 
 #include <asm/kvm_asm.h>
 #include <asm/kvm_emulate.h>
@@ -308,6 +309,18 @@ again:
        if (exit_code == ARM_EXCEPTION_TRAP && !__populate_fault_info(vcpu))
                goto again;
 
+       if (exit_code == ARM_EXCEPTION_TRAP &&
+           (kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_HVC64 ||
+            kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_HVC32) &&
+           vcpu_get_reg(vcpu, 0) == PSCI_0_2_FN_PSCI_VERSION) {
+               u64 val = PSCI_RET_NOT_SUPPORTED;
+               if (test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features))
+                       val = 2;
+
+               vcpu_set_reg(vcpu, 0, val);
+               goto again;
+       }
+
        if (static_branch_unlikely(&vgic_v2_cpuif_trap) &&
            exit_code == ARM_EXCEPTION_TRAP) {
                bool valid;