[v4.9.y,27/42] arm64: KVM: Increment PC after handling an SMC trap

Message ID 20180412111138.40990-28-mark.rutland@arm.com
State New
Headers show
Series
  • arm64 spectre patches
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Commit Message

Mark Rutland April 12, 2018, 11:11 a.m.
From: Marc Zyngier <marc.zyngier@arm.com>


commit f5115e8869e1dfafac0e414b4f1664f3a84a4683 upstream.

When handling an SMC trap, the "preferred return address" is set
to that of the SMC, and not the next PC (which is a departure from
the behaviour of an SMC that isn't trapped).

Increment PC in the handler, as the guest is otherwise forever
stuck...

Cc: stable@vger.kernel.org
Fixes: acfb3b883f6d ("arm64: KVM: Fix SMCCC handling of unimplemented SMC/HVC calls")
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>

Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Signed-off-by: Mark Rutland <mark.rutland@arm.com> [v4.9 backport]

---
 arch/arm64/kvm/handle_exit.c | 9 +++++++++
 1 file changed, 9 insertions(+)

-- 
2.11.0

Patch

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 2e6e9e99977b..5b56b09d317b 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -53,7 +53,16 @@  static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
 
 static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
 {
+	/*
+	 * "If an SMC instruction executed at Non-secure EL1 is
+	 * trapped to EL2 because HCR_EL2.TSC is 1, the exception is a
+	 * Trap exception, not a Secure Monitor Call exception [...]"
+	 *
+	 * We need to advance the PC after the trap, as it would
+	 * otherwise return to the same address...
+	 */
 	vcpu_set_reg(vcpu, 0, ~0UL);
+	kvm_skip_instr(vcpu, kvm_vcpu_trap_il_is32bit(vcpu));
 	return 1;
 }