4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Mark Rutland <mark.rutl...@arm.com>
From: Marc Zyngier <marc.zyng...@arm.com>
commit 6167ec5c9145cdf493722dfd80a5d48bafc4a18a upstream.
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.biesheu...@linaro.org>
Reviewed-by: Christoffer Dall <christoffer.d...@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyng...@arm.com>
Signed-off-by: Catalin Marinas <catalin.mari...@arm.com>
[v4.9: account for files moved to virt/ upstream]
Signed-off-by: Mark Rutland <mark.rutl...@arm.com> [v4.9 backport]
Tested-by: Greg Hackmann <ghackm...@google.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
arch/arm/include/asm/kvm_host.h | 6 ++++++
arch/arm/kvm/psci.c | 9 ++++++++-
arch/arm64/include/asm/kvm_host.h | 5 +++++
include/linux/arm-smccc.h | 5 +++++
4 files changed, 24 insertions(+), 1 deletion(-)
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -318,4 +318,10 @@ static inline int kvm_arm_vcpu_arch_has_
return -ENXIO;
}
+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__ */
--- a/arch/arm/kvm/psci.c
+++ b/arch/arm/kvm/psci.c
@@ -403,13 +403,20 @@ int kvm_hvc_call_handler(struct kvm_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);
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -393,4 +393,9 @@ static inline void __cpu_init_stage2(voi
"PARange is %d bits, unsupported configuration!", parange);
}
+static inline bool kvm_arm_harden_branch_predictor(void)
+{
+ return cpus_have_cap(ARM64_HARDEN_BRANCH_PREDICTOR);
+}
+
#endif /* __ARM64_KVM_HOST_H__ */
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -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>
