[v4.4,29/45] arm64: KVM: Increment PC after handling an SMC trap

Message ID 2798950c13d82c9e5b4c9a94afe8eeeef052283a.1560480942.git.viresh.kumar@linaro.org
State New
Headers show
  • V4.4 backport of arm64 Spectre patches
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Commit Message

Viresh Kumar June 14, 2019, 3:08 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

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: Viresh Kumar <viresh.kumar@linaro.org>

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



diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 5295aef7c8f0..c43e0e100c11 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -51,7 +51,16 @@  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;