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KVM: x86/mmu: Move "invalid" check out of kvm_tdp_mmu_get_root()

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commit 04dc4e6ce2 upstream.

Move the check for an invalid root out of kvm_tdp_mmu_get_root() and into
the one place it actually matters, tdp_mmu_next_root(), as the other user
already has an implicit validity check.  A future bug fix will need to
get references to invalid roots to honor mmu_notifier requests; there's
no point in forcing what will be a common path to open code getting a
reference to a root.

No functional change intended.

Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211215011557.399940-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sean Christopherson 2021-12-15 01:15:55 +00:00 committed by Greg Kroah-Hartman
parent b441a8809c
commit 2bccda7d37
2 changed files with 10 additions and 5 deletions
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12
arch/x86/kvm/mmu/tdp_mmu.c
View file

@ -121,9 +121,14 @@ static struct kvm_mmu_page *tdp_mmu_next_root(struct kvm *kvm,
next_root = list_first_or_null_rcu(&kvm->arch.tdp_mmu_roots,
typeof(*next_root), link);
while (next_root && !kvm_tdp_mmu_get_root(kvm, next_root))
while (next_root) {
if (!next_root->role.invalid &&
kvm_tdp_mmu_get_root(kvm, next_root))
break;
next_root = list_next_or_null_rcu(&kvm->arch.tdp_mmu_roots,
&next_root->link, typeof(*next_root), link);
}
rcu_read_unlock();
@ -200,7 +205,10 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu)
role = page_role_for_level(vcpu, vcpu->arch.mmu->shadow_root_level);
/* Check for an existing root before allocating a new one. */
/*
* Check for an existing root before allocating a new one. Note, the
* role check prevents consuming an invalid root.
*/
for_each_tdp_mmu_root(kvm, root, kvm_mmu_role_as_id(role)) {
if (root->role.word == role.word &&
kvm_tdp_mmu_get_root(kvm, root))

3
arch/x86/kvm/mmu/tdp_mmu.h
View file

@ -10,9 +10,6 @@ hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu);
__must_check static inline bool kvm_tdp_mmu_get_root(struct kvm *kvm,
struct kvm_mmu_page *root)
{
if (root->role.invalid)
return false;
return refcount_inc_not_zero(&root->tdp_mmu_root_count);
}