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KVM: arm64: Hoist MTE validation check out of MMU lock path

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Simplify the non-cacheable attributes assignment by using a ternary
operator. Additionally, hoist the MTE validation check (mte_allowed) out
of kvm_s2_fault_map() and into kvm_s2_fault_compute_prot(). This allows
us to fail faster and avoid acquiring the KVM MMU lock unnecessarily
when the VMM introduces a disallowed VMA for an MTE-enabled guest.

Signed-off-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Fuad Tabba 2026-03-06 14:02:31 +00:00 committed by Marc Zyngier
parent 3456943e87
commit 84699747aa
1 changed files with 12 additions and 16 deletions
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28
arch/arm64/kvm/mmu.c
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@ -1870,18 +1870,21 @@ static int kvm_s2_fault_compute_prot(struct kvm_s2_fault *fault)
if (fault->exec_fault)
fault->prot |= KVM_PGTABLE_PROT_X;
if (fault->s2_force_noncacheable) {
if (fault->vm_flags & VM_ALLOW_ANY_UNCACHED)
fault->prot |= KVM_PGTABLE_PROT_NORMAL_NC;
else
fault->prot |= KVM_PGTABLE_PROT_DEVICE;
} else if (cpus_have_final_cap(ARM64_HAS_CACHE_DIC)) {
if (fault->s2_force_noncacheable)
fault->prot |= (fault->vm_flags & VM_ALLOW_ANY_UNCACHED) ?
KVM_PGTABLE_PROT_NORMAL_NC : KVM_PGTABLE_PROT_DEVICE;
else if (cpus_have_final_cap(ARM64_HAS_CACHE_DIC))
fault->prot |= KVM_PGTABLE_PROT_X;
}
if (fault->nested)
adjust_nested_exec_perms(kvm, fault->nested, &fault->prot);
if (!fault->fault_is_perm && !fault->s2_force_noncacheable && kvm_has_mte(kvm)) {
/* Check the VMM hasn't introduced a new disallowed VMA */
if (!fault->mte_allowed)
return -EFAULT;
}
return 0;
}
@ -1918,15 +1921,8 @@ static int kvm_s2_fault_map(struct kvm_s2_fault *fault, void *memcache)
}
}
if (!fault->fault_is_perm && !fault->s2_force_noncacheable && kvm_has_mte(kvm)) {
/* Check the VMM hasn't introduced a new disallowed VMA */
if (fault->mte_allowed) {
sanitise_mte_tags(kvm, fault->pfn, fault->vma_pagesize);
} else {
ret = -EFAULT;
goto out_unlock;
}
}
if (!fault->fault_is_perm && !fault->s2_force_noncacheable && kvm_has_mte(kvm))
sanitise_mte_tags(kvm, fault->pfn, fault->vma_pagesize);
/*
* Under the premise of getting a FSC_PERM fault, we just need to relax