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Commit 6167ec5c authored by Marc Zyngier's avatar Marc Zyngier Committed by Catalin Marinas
Browse files

arm64: KVM: Report SMCCC_ARCH_WORKAROUND_1 BP hardening support 



A new feature of SMCCC 1.1 is that it offers firmware-based CPU
workarounds. In particular, SMCCC_ARCH_WORKAROUND_1 provides
BP hardening for CVE-2017-5715.

If the host has some mitigation for this issue, report that
we deal with it using SMCCC_ARCH_WORKAROUND_1, as we apply the
host workaround on every guest exit.

Tested-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent a4097b35

arch/arm/include/asm/kvm_host.h

+7 −0
Original line number Diff line number Diff line
@@ -306,4 +306,11 @@ static inline void kvm_fpsimd_flush_cpu_state(void) {} 


static inline void kvm_arm_vhe_guest_enter(void) {}

static inline void kvm_arm_vhe_guest_exit(void) {}



static inline bool kvm_arm_harden_branch_predictor(void)

{

	/* No way to detect it yet, pretend it is not there. */

	return false;

}



#endif /* __ARM_KVM_HOST_H__ */

arch/arm64/include/asm/kvm_host.h

+6 −0
Original line number Diff line number Diff line
@@ -415,4 +415,10 @@ static inline void kvm_arm_vhe_guest_exit(void) 
{

	local_daif_restore(DAIF_PROCCTX_NOIRQ);

}



static inline bool kvm_arm_harden_branch_predictor(void)

{

	return cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR);

}



#endif /* __ARM64_KVM_HOST_H__ */

include/linux/arm-smccc.h

+5 −0
Original line number Diff line number Diff line
@@ -73,6 +73,11 @@ 
			   ARM_SMCCC_SMC_32,				\

			   0, 1)



#define ARM_SMCCC_ARCH_WORKAROUND_1					\

	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\

			   ARM_SMCCC_SMC_32,				\

			   0, 0x8000)



#ifndef __ASSEMBLY__



#include <linux/linkage.h>

virt/kvm/arm/psci.c

+8 −1
Original line number Diff line number Diff line
@@ -405,13 +405,20 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) 
{

	u32 func_id = smccc_get_function(vcpu);

	u32 val = PSCI_RET_NOT_SUPPORTED;

	u32 feature;



	switch (func_id) {

	case ARM_SMCCC_VERSION_FUNC_ID:

		val = ARM_SMCCC_VERSION_1_1;

		break;

	case ARM_SMCCC_ARCH_FEATURES_FUNC_ID:

		/* Nothing supported yet */

		feature = smccc_get_arg1(vcpu);

		switch(feature) {

		case ARM_SMCCC_ARCH_WORKAROUND_1:

			if (kvm_arm_harden_branch_predictor())

				val = 0;

			break;

		}

		break;

	default:

		return kvm_psci_call(vcpu);