From: Will Deacon <will@kernel.org>
To: kvmarm@lists.cs.columbia.edu
Subject: [PATCH] KVM: arm64: Really propagate PSCI SYSTEM_RESET2 arguments to
 userspace
Date: Wed,  9 Mar 2022 18:13:08 +0000
Message-Id: <20220309181308.982-1-will@kernel.org>
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Cc: maz@kernel.org, Will Deacon <will@kernel.org>,
 Andrew Walbran <qwandor@google.com>, linux-arm-kernel@lists.infradead.org
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Commit d43583b890e7 ("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: d43583b890e7 ("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>
---
 arch/arm64/kvm/psci.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index ecb4b74cb12a..b0c920717632 100644
--- 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;
-- 
2.35.1.616.g0bdcbb4464-goog

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