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Commit 20e8175d authored by Marc Zyngier's avatar Marc Zyngier Committed by Catalin Marinas
Browse files

arm: KVM: Fix SMCCC handling of unimplemented SMC/HVC calls 



KVM doesn't follow the SMCCC when it comes to unimplemented calls,
and inject an UNDEF instead of returning an error. Since firmware
calls are now used for security mitigation, they are becoming more
common, and the undef is counter productive.

Instead, let's follow the SMCCC which states that -1 must be returned
to the caller when getting an unknown function number.

Cc: <stable@vger.kernel.org>
Tested-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent c0938c72

arch/arm/kvm/handle_exit.c

+11 −2
Original line number Diff line number Diff line
@@ -38,7 +38,7 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run) 


	ret = kvm_psci_call(vcpu);

	if (ret < 0) {

		kvm_inject_undefined(vcpu);

		vcpu_set_reg(vcpu, 0, ~0UL);

		return 1;

	}
@@ -47,7 +47,16 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run) 


static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)

{

	kvm_inject_undefined(vcpu);

	/*

	 * "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;

}