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KVM: x86/mmu: Zap invalid roots with mmu_lock holding for write at uninit

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Prepare for a future TDX patch which asserts that atomic zapping
(i.e. zapping with mmu_lock taken for read) don't operate on mirror roots.
When tearing down a VM, all roots have to be zapped (including mirror
roots once they're in place) so do that with the mmu_lock taken for write.

kvm_mmu_uninit_tdp_mmu() is invoked either before or after executing any
atomic operations on SPTEs by vCPU threads. Therefore, it will not impact
vCPU threads performance if kvm_tdp_mmu_zap_invalidated_roots() acquires
mmu_lock for write to zap invalid roots.

Co-developed-by: Yan Zhao <yan.y.zhao@intel.com>
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Message-ID: <20240718211230.1492011-2-rick.p.edgecombe@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Rick Edgecombe
2024-07-18 14:12:13 -07:00
committed by Paolo Bonzini
parent 67b43038ce
commit 35be969d1e
3 changed files with 13 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/kvm/mmu/mmu.c
View File

@@ -6467,7 +6467,7 @@ static void kvm_mmu_zap_all_fast(struct kvm *kvm)
* lead to use-after-free.
*/
if (tdp_mmu_enabled)
kvm_tdp_mmu_zap_invalidated_roots(kvm);
kvm_tdp_mmu_zap_invalidated_roots(kvm, true);
}
void kvm_mmu_init_vm(struct kvm *kvm)

16
arch/x86/kvm/mmu/tdp_mmu.c
View File

@@ -38,7 +38,7 @@ void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm)
* ultimately frees all roots.
*/
kvm_tdp_mmu_invalidate_all_roots(kvm);
kvm_tdp_mmu_zap_invalidated_roots(kvm);
kvm_tdp_mmu_zap_invalidated_roots(kvm, false);
WARN_ON(atomic64_read(&kvm->arch.tdp_mmu_pages));
WARN_ON(!list_empty(&kvm->arch.tdp_mmu_roots));
@@ -883,11 +883,14 @@ void kvm_tdp_mmu_zap_all(struct kvm *kvm)
* Zap all invalidated roots to ensure all SPTEs are dropped before the "fast
* zap" completes.
*/
void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm)
void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm, bool shared)
{
struct kvm_mmu_page *root;
read_lock(&kvm->mmu_lock);
if (shared)
read_lock(&kvm->mmu_lock);
else
write_lock(&kvm->mmu_lock);
for_each_tdp_mmu_root_yield_safe(kvm, root) {
if (!root->tdp_mmu_scheduled_root_to_zap)
@@ -905,7 +908,7 @@ void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm)
* that may be zapped, as such entries are associated with the
* ASID on both VMX and SVM.
*/
tdp_mmu_zap_root(kvm, root, true);
tdp_mmu_zap_root(kvm, root, shared);
/*
* The referenced needs to be put *after* zapping the root, as
@@ -915,7 +918,10 @@ void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm)
kvm_tdp_mmu_put_root(kvm, root);
}
read_unlock(&kvm->mmu_lock);
if (shared)
read_unlock(&kvm->mmu_lock);
else
write_unlock(&kvm->mmu_lock);
}
/*

2
arch/x86/kvm/mmu/tdp_mmu.h
View File

@@ -23,7 +23,7 @@ bool kvm_tdp_mmu_zap_leafs(struct kvm *kvm, gfn_t start, gfn_t end, bool flush);
bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp);
void kvm_tdp_mmu_zap_all(struct kvm *kvm);
void kvm_tdp_mmu_invalidate_all_roots(struct kvm *kvm);
void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm);
void kvm_tdp_mmu_zap_invalidated_roots(struct kvm *kvm, bool shared);
int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault);