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| author | Sean Christopherson <seanjc@google.com> | 2024-01-11 03:00:46 +0100 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2024-02-23 01:28:45 +0100 |
| commit | f5238c2a60f1e0eb48ce21037bce6f4781afa37f (patch) | |
| tree | 0c4b42d809c9aea798d8213540c903af985551d7 /arch/x86/kvm/mmu/mmu.c | |
| parent | KVM: x86/mmu: Skip invalid TDP MMU roots when write-protecting SPTEs (diff) | |
| download | linux-f5238c2a60f1e0eb48ce21037bce6f4781afa37f.tar.xz linux-f5238c2a60f1e0eb48ce21037bce6f4781afa37f.zip | |
KVM: x86/mmu: Check for usable TDP MMU root while holding mmu_lock for read
When allocating a new TDP MMU root, check for a usable root while holding
mmu_lock for read and only acquire mmu_lock for write if a new root needs
to be created. There is no need to serialize other MMU operations if a
vCPU is simply grabbing a reference to an existing root, holding mmu_lock
for write is "necessary" (spoiler alert, it's not strictly necessary) only
to ensure KVM doesn't end up with duplicate roots.
Allowing vCPUs to get "new" roots in parallel is beneficial to VM boot and
to setups that frequently delete memslots, i.e. which force all vCPUs to
reload all roots.
Link: https://lore.kernel.org/r/20240111020048.844847-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/x86/kvm/mmu/mmu.c')
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 3c193b096b45..c9150080fbd2 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3693,15 +3693,15 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu) unsigned i; int r; + if (tdp_mmu_enabled) + return kvm_tdp_mmu_alloc_root(vcpu); + write_lock(&vcpu->kvm->mmu_lock); r = make_mmu_pages_available(vcpu); if (r < 0) goto out_unlock; - if (tdp_mmu_enabled) { - root = kvm_tdp_mmu_get_vcpu_root_hpa(vcpu); - mmu->root.hpa = root; - } else if (shadow_root_level >= PT64_ROOT_4LEVEL) { + if (shadow_root_level >= PT64_ROOT_4LEVEL) { root = mmu_alloc_root(vcpu, 0, 0, shadow_root_level); mmu->root.hpa = root; } else if (shadow_root_level == PT32E_ROOT_LEVEL) { |