[PATCH v2 10/16] arm64: KVM: Report SMCCC_ARCH_WORKAROUND_1 BP hardening support
From: robin.murphy@arm.com (Robin Murphy)
Date: 2018-01-30 12:38:40
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kvmarm, lkml
On 29/01/18 17:45, Marc Zyngier wrote:
quoted hunk ↗ jump to hunk
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. Signed-off-by: Marc Zyngier <redacted> --- include/linux/arm-smccc.h | 5 +++++ virt/kvm/arm/psci.c | 17 +++++++++++++++-- 2 files changed, 20 insertions(+), 2 deletions(-)diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h index dc68aa5a7261..e1ef944ef1da 100644 --- 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>diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c index a021b62ed762..5677d16abc71 100644 --- a/virt/kvm/arm/psci.c +++ b/virt/kvm/arm/psci.c@@ -407,14 +407,27 @@ static int kvm_psci_call(struct kvm_vcpu *vcpu) int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) { u32 func_id = smccc_get_function(vcpu); - u32 val; + u32 val, feature; switch (func_id) { case ARM_SMCCC_VERSION_FUNC_ID: val = ARM_SMCCC_VERSION_1_1; break; case ARM_SMCCC_ARCH_FEATURES_FUNC_ID: - val = -1; /* Nothing supported yet */
Conceptually, might it still make sense to initialise val to NOT_SUPPORTED here, then overwrite it if and when a feature actually is present? It would in this case save a few lines as well, but I know multiple assignment can be one of those religious issues, so I'm not too fussed either way. Robin.
+ feature = smccc_get_arg1(vcpu);
+ switch(feature) {
+#ifdef CONFIG_ARM64
+ case ARM_SMCCC_ARCH_WORKAROUND_1:
+ if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR))
+ val = 0;
+ else
+ val = -1;
+ break;
+#endif
+ default:
+ val = -1;
+ break;
+ }
break;
default:
return kvm_psci_call(vcpu);