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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: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Marc Zyngier 2018-02-06 17:56:14 +00:00 committed by Catalin Marinas
parent a4097b3511
commit 6167ec5c91
4 changed files with 26 additions and 1 deletions
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7
arch/arm/include/asm/kvm_host.h
View File

@ -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_enter(void) {}
static inline void kvm_arm_vhe_guest_exit(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__ */ #endif /* __ARM_KVM_HOST_H__ */

6
arch/arm64/include/asm/kvm_host.h
View File

@ -415,4 +415,10 @@ static inline void kvm_arm_vhe_guest_exit(void)
{ {
local_daif_restore(DAIF_PROCCTX_NOIRQ); 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__ */ #endif /* __ARM64_KVM_HOST_H__ */

5
include/linux/arm-smccc.h
View File

@ -73,6 +73,11 @@
ARM_SMCCC_SMC_32, \ ARM_SMCCC_SMC_32, \
0, 1) 0, 1)
#define ARM_SMCCC_ARCH_WORKAROUND_1 \
ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
ARM_SMCCC_SMC_32, \
0, 0x8000)
#ifndef __ASSEMBLY__ #ifndef __ASSEMBLY__
#include <linux/linkage.h> #include <linux/linkage.h>

9
virt/kvm/arm/psci.c
View File

@ -405,13 +405,20 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
{ {
u32 func_id = smccc_get_function(vcpu); u32 func_id = smccc_get_function(vcpu);
u32 val = PSCI_RET_NOT_SUPPORTED; u32 val = PSCI_RET_NOT_SUPPORTED;
u32 feature;
switch (func_id) { switch (func_id) {
case ARM_SMCCC_VERSION_FUNC_ID: case ARM_SMCCC_VERSION_FUNC_ID:
val = ARM_SMCCC_VERSION_1_1; val = ARM_SMCCC_VERSION_1_1;
break; break;
case ARM_SMCCC_ARCH_FEATURES_FUNC_ID: 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; break;
default: default:
return kvm_psci_call(vcpu); return kvm_psci_call(vcpu);