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KVM: arm64: Only insert reserved ranges when SMCCC filter is used

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The reserved ranges are only useful for preventing userspace from
adding a rule that intersects with functions we must handle in KVM. If
userspace never writes to the SMCCC filter than this is all just wasted
work/memory.

Insert reserved ranges on the first call to KVM_ARM_VM_SMCCC_FILTER.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20231004234947.207507-3-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Oliver Upton
2023-10-04 23:49:46 +00:00
parent bb17fb31f0
commit d34b76489e
1 changed files with 16 additions and 6 deletions
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22
arch/arm64/kvm/hypercalls.c
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@@ -133,12 +133,10 @@ static bool kvm_smccc_test_fw_bmap(struct kvm_vcpu *vcpu, u32 func_id)
ARM_SMCCC_SMC_64, \
0, ARM_SMCCC_FUNC_MASK)
static void init_smccc_filter(struct kvm *kvm)
static int kvm_smccc_filter_insert_reserved(struct kvm *kvm)
{
int r;
mt_init(&kvm->arch.smccc_filter);
/*
* Prevent userspace from handling any SMCCC calls in the architecture
* range, avoiding the risk of misrepresenting Spectre mitigation status
@@ -148,14 +146,20 @@ static void init_smccc_filter(struct kvm *kvm)
SMC32_ARCH_RANGE_BEGIN, SMC32_ARCH_RANGE_END,
xa_mk_value(KVM_SMCCC_FILTER_HANDLE),
GFP_KERNEL_ACCOUNT);
WARN_ON_ONCE(r);
if (r)
goto out_destroy;
r = mtree_insert_range(&kvm->arch.smccc_filter,
SMC64_ARCH_RANGE_BEGIN, SMC64_ARCH_RANGE_END,
xa_mk_value(KVM_SMCCC_FILTER_HANDLE),
GFP_KERNEL_ACCOUNT);
WARN_ON_ONCE(r);
if (r)
goto out_destroy;
return 0;
out_destroy:
mtree_destroy(&kvm->arch.smccc_filter);
return r;
}
static bool kvm_smccc_filter_configured(struct kvm *kvm)
@@ -189,6 +193,12 @@ static int kvm_smccc_set_filter(struct kvm *kvm, struct kvm_smccc_filter __user
goto out_unlock;
}
if (!kvm_smccc_filter_configured(kvm)) {
r = kvm_smccc_filter_insert_reserved(kvm);
if (WARN_ON_ONCE(r))
goto out_unlock;
}
r = mtree_insert_range(&kvm->arch.smccc_filter, start, end,
xa_mk_value(filter.action), GFP_KERNEL_ACCOUNT);
if (r)
@@ -392,7 +402,7 @@ void kvm_arm_init_hypercalls(struct kvm *kvm)
smccc_feat->std_hyp_bmap = KVM_ARM_SMCCC_STD_HYP_FEATURES;
smccc_feat->vendor_hyp_bmap = KVM_ARM_SMCCC_VENDOR_HYP_FEATURES;
init_smccc_filter(kvm);
mt_init(&kvm->arch.smccc_filter);
}
void kvm_arm_teardown_hypercalls(struct kvm *kvm)