KVM: arm64: Really propagate PSCI SYSTEM_RESET2 arguments to userspace

Commit ed47efd863d9 ("KVM: arm64: Expose PSCI SYSTEM_RESET2 call to the
guest") hooked up the SYSTEM_RESET2 PSCI call for guests but failed to
preserve its arguments for userspace, instead overwriting them with
zeroes via smccc_set_retval(). As Linux only passes zeroes for these
arguments, this appeared to be working for Linux guests. Oh well.

Don't call smccc_set_retval() for a SYSTEM_RESET2 heading to userspace
and instead set X0 (and only X0) explicitly to PSCI_RET_INTERNAL_FAILURE
just in case the vCPU re-enters the guest.

Fixes: ed47efd863d9 ("KVM: arm64: Expose PSCI SYSTEM_RESET2 call to the guest")
Reported-by: Andrew Walbran <qwandor@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220309181308.982-1-will@kernel.org

diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index 0d48d1e7291d5ad18ade9279fabc969e3a96b2cf..3e007d6982af06698360d528a369645446afe43c 100644 (file)
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -367,14 +367,14 @@ static int kvm_psci_1_x_call(struct kvm_vcpu *vcpu, u32 minor)
                if (minor >= 1) {
                        arg = smccc_get_arg1(vcpu);
 
-                       if (arg > PSCI_1_1_RESET_TYPE_SYSTEM_WARM_RESET &&
-                           arg < PSCI_1_1_RESET_TYPE_VENDOR_START) {
-                               val = PSCI_RET_INVALID_PARAMS;
-                       } else {
+                       if (arg <= PSCI_1_1_RESET_TYPE_SYSTEM_WARM_RESET ||
+                           arg >= PSCI_1_1_RESET_TYPE_VENDOR_START) {
                                kvm_psci_system_reset2(vcpu);
-                               val = PSCI_RET_INTERNAL_FAILURE;
-                               ret = 0;
+                               vcpu_set_reg(vcpu, 0, PSCI_RET_INTERNAL_FAILURE);
+                               return 0;
                        }
+
+                       val = PSCI_RET_INVALID_PARAMS;
                        break;
                }
                fallthrough;