Messages in this thread |  | | Subject | Re: [PATCH v2 10/16] arm64: KVM: Report SMCCC_ARCH_WORKAROUND_1 BP hardening support | From | Robin Murphy <> | Date | Tue, 30 Jan 2018 12:38:35 +0000 |
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On 29/01/18 17:45, Marc Zyngier wrote: > 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 <marc.zyngier@arm.com> > --- > 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); >
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