Commit fdc9999e authored by Marc Zyngier's avatar Marc Zyngier
Browse files

KVM: arm64: PSCI: Forbid 64bit functions for 32bit guests 



Implementing (and even advertising) 64bit PSCI functions to 32bit
guests is at least a bit odd, if not altogether violating the
spec which says ("5.2.1 Register usage in arguments and return values"):

"Adherence to the SMC Calling Conventions implies that any AArch32
caller of an SMC64 function will get a return code of 0xFFFFFFFF(int32).
This matches the NOT_SUPPORTED error code used in PSCI"

Tighten the implementation by pretending these functions are not
there for 32bit guests.

Reviewed-by: default avatarChristoffer Dall <christoffer.dall@arm.com>
Reviewed-by: default avatarAlexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 2890ac99

virt/kvm/arm/psci.c

+24 −0
Original line number Diff line number Diff line
@@ -198,6 +198,21 @@ static void kvm_psci_narrow_to_32bit(struct kvm_vcpu *vcpu) 
		vcpu_set_reg(vcpu, i, lower_32_bits(vcpu_get_reg(vcpu, i)));

}



static unsigned long kvm_psci_check_allowed_function(struct kvm_vcpu *vcpu, u32 fn)

{

	switch(fn) {

	case PSCI_0_2_FN64_CPU_SUSPEND:

	case PSCI_0_2_FN64_CPU_ON:

	case PSCI_0_2_FN64_AFFINITY_INFO:

		/* Disallow these functions for 32bit guests */

		if (vcpu_mode_is_32bit(vcpu))

			return PSCI_RET_NOT_SUPPORTED;

		break;

	}



	return 0;

}



static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)

{

	struct kvm *kvm = vcpu->kvm;
@@ -205,6 +220,10 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) 
	unsigned long val;

	int ret = 1;



	val = kvm_psci_check_allowed_function(vcpu, psci_fn);

	if (val)

		goto out;



	switch (psci_fn) {

	case PSCI_0_2_FN_PSCI_VERSION:

		/*
@@ -272,6 +291,7 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu) 
		break;

	}



out:

	smccc_set_retval(vcpu, val, 0, 0, 0);

	return ret;

}
@@ -289,6 +309,10 @@ static int kvm_psci_1_0_call(struct kvm_vcpu *vcpu) 
		break;

	case PSCI_1_0_FN_PSCI_FEATURES:

		feature = smccc_get_arg1(vcpu);

		val = kvm_psci_check_allowed_function(vcpu, feature);

		if (val)

			break;



		switch(feature) {

		case PSCI_0_2_FN_PSCI_VERSION:

		case PSCI_0_2_FN_CPU_SUSPEND:

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