diff options
| author | Sean Christopherson <seanjc@google.com> | 2021-08-23 17:58:24 -0700 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2021-09-06 05:56:38 -0400 |
| commit | a717a780fc4e1dddd3fbf9ad08f180eec2a78194 (patch) | |
| tree | 7eeb7a6e4ffb8e8686152dcb91d1ff88f4721a11 /arch | |
| parent | 43e540cc9f2ca12a2364ddf64e5ef929a546550d (diff) | |
KVM: x86/mmu: Don't freak out if pml5_root is NULL on 4-level host
Include pml5_root in the set of special roots if and only if the host,
and thus NPT, is using 5-level paging. mmu_alloc_special_roots() expects
special roots to be allocated as a bundle, i.e. they're either all valid
or all NULL. But for pml5_root, that expectation only holds true if the
host uses 5-level paging, which causes KVM to WARN about pml5_root being
NULL when the other special roots are valid.
The silver lining of 4-level vs. 5-level NPT being tied to the host
kernel's paging level is that KVM's shadow root level is constant; unlike
VMX's EPT, KVM can't choose 4-level NPT based on guest.MAXPHYADDR. That
means KVM can still expect pml5_root to be bundled with the other special
roots, it just needs to be conditioned on the shadow root level.
Fixes: cb0f722aff6e ("KVM: x86/mmu: Support shadowing NPT when 5-level paging is enabled in host")
Reported-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210824005824.205536-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index c04e30f6e0db..e7bac871747c 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3588,6 +3588,7 @@ out_unlock: static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu) { struct kvm_mmu *mmu = vcpu->arch.mmu; + bool need_pml5 = mmu->shadow_root_level > PT64_ROOT_4LEVEL; u64 *pml5_root = NULL; u64 *pml4_root = NULL; u64 *pae_root; @@ -3602,7 +3603,14 @@ static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu) mmu->shadow_root_level < PT64_ROOT_4LEVEL) return 0; - if (mmu->pae_root && mmu->pml4_root && mmu->pml5_root) + /* + * NPT, the only paging mode that uses this horror, uses a fixed number + * of levels for the shadow page tables, e.g. all MMUs are 4-level or + * all MMus are 5-level. Thus, this can safely require that pml5_root + * is allocated if the other roots are valid and pml5 is needed, as any + * prior MMU would also have required pml5. + */ + if (mmu->pae_root && mmu->pml4_root && (!need_pml5 || mmu->pml5_root)) return 0; /* @@ -3610,7 +3618,7 @@ static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu) * bail if KVM ends up in a state where only one of the roots is valid. */ if (WARN_ON_ONCE(!tdp_enabled || mmu->pae_root || mmu->pml4_root || - mmu->pml5_root)) + (need_pml5 && mmu->pml5_root))) return -EIO; /* @@ -3626,7 +3634,7 @@ static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu) if (!pml4_root) goto err_pml4; - if (mmu->shadow_root_level > PT64_ROOT_4LEVEL) { + if (need_pml5) { pml5_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT); if (!pml5_root) goto err_pml5; |