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KVM: x86/mmu: Allocate pae_root and lm_root pages in dedicated helper

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Move the on-demand allocation of the pae_root and lm_root pages, used by
nested NPT for 32-bit L1s, into a separate helper.  This will allow a
future patch to hold mmu_lock while allocating the non-special roots so
that make_mmu_pages_available() can be checked once at the start of root
allocation, and thus avoid having to deal with failure in the middle of
root allocation.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2021-03-04 17:10:49 -08:00 committed by Paolo Bonzini
parent ba0a194ffb
commit 748e52b9b7
1 changed files with 54 additions and 30 deletions
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84
arch/x86/kvm/mmu/mmu.c
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@ -3314,38 +3314,10 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
* the shadow page table may be a PAE or a long mode page table.
*/
pm_mask = PT_PRESENT_MASK;
if (mmu->shadow_root_level == PT64_ROOT_4LEVEL)
if (mmu->shadow_root_level == PT64_ROOT_4LEVEL) {
pm_mask |= PT_ACCESSED_MASK | PT_WRITABLE_MASK | PT_USER_MASK;
/*
* When shadowing 32-bit or PAE NPT with 64-bit NPT, the PML4 and PDP
* tables are allocated and initialized at root creation as there is no
* equivalent level in the guest's NPT to shadow. Allocate the tables
* on demand, as running a 32-bit L1 VMM is very rare. Unlike 32-bit
* NPT, the PDP table doesn't need to be in low mem. Preallocate the
* pages so that the PAE roots aren't leaked on failure.
*/
if (mmu->shadow_root_level == PT64_ROOT_4LEVEL &&
(!mmu->pae_root || !mmu->lm_root)) {
u64 *lm_root, *pae_root;
if (WARN_ON_ONCE(!tdp_enabled || mmu->pae_root || mmu->lm_root))
return -EIO;
pae_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
if (!pae_root)
return -ENOMEM;
lm_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
if (!lm_root) {
free_page((unsigned long)pae_root);
return -ENOMEM;
}
mmu->pae_root = pae_root;
mmu->lm_root = lm_root;
lm_root[0] = __pa(mmu->pae_root) | pm_mask;
mmu->lm_root[0] = __pa(mmu->pae_root) | pm_mask;
}
for (i = 0; i < 4; ++i) {
@ -3379,6 +3351,55 @@ set_root_pgd:
return 0;
}
static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu)
{
struct kvm_mmu *mmu = vcpu->arch.mmu;
u64 *lm_root, *pae_root;
/*
* When shadowing 32-bit or PAE NPT with 64-bit NPT, the PML4 and PDP
* tables are allocated and initialized at root creation as there is no
* equivalent level in the guest's NPT to shadow. Allocate the tables
* on demand, as running a 32-bit L1 VMM on 64-bit KVM is very rare.
*/
if (mmu->direct_map || mmu->root_level >= PT64_ROOT_4LEVEL ||
mmu->shadow_root_level < PT64_ROOT_4LEVEL)
return 0;
/*
* This mess only works with 4-level paging and needs to be updated to
* work with 5-level paging.
*/
if (WARN_ON_ONCE(mmu->shadow_root_level != PT64_ROOT_4LEVEL))
return -EIO;
if (mmu->pae_root && mmu->lm_root)
return 0;
/*
* The special roots should always be allocated in concert. Yell and
* 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->lm_root))
return -EIO;
/* Unlike 32-bit NPT, the PDP table doesn't need to be in low mem. */
pae_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
if (!pae_root)
return -ENOMEM;
lm_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
if (!lm_root) {
free_page((unsigned long)pae_root);
return -ENOMEM;
}
mmu->pae_root = pae_root;
mmu->lm_root = lm_root;
return 0;
}
static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
{
if (vcpu->arch.mmu->direct_map)
@ -4812,6 +4833,9 @@ int kvm_mmu_load(struct kvm_vcpu *vcpu)
int r;
r = mmu_topup_memory_caches(vcpu, !vcpu->arch.mmu->direct_map);
if (r)
goto out;
r = mmu_alloc_special_roots(vcpu);
if (r)
goto out;
r = mmu_alloc_roots(vcpu);