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KVM: x86/mmu: Allocate the lm_root before allocating PAE roots

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Allocate lm_root before the PAE roots so that the PAE roots aren't
leaked if the memory allocation for the lm_root happens to fail.

Note, KVM can still leak PAE roots if mmu_check_root() fails on a guest's
PDPTR, or if mmu_alloc_root() fails due to MMU pages not being available.
Those issues will be fixed in future commits.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-5-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2021-03-04 17:10:48 -08:00 committed by Paolo Bonzini
parent b37233c911
commit ba0a194ffb
1 changed files with 31 additions and 33 deletions
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64
arch/x86/kvm/mmu/mmu.c
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@ -3314,21 +3314,38 @@ 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;
/*
* Allocate the page for the PDPTEs when shadowing 32-bit NPT
* with 64-bit only when needed. Unlike 32-bit NPT, it doesn't
* need to be in low mem. See also lm_root below.
*/
if (!mmu->pae_root) {
WARN_ON_ONCE(!tdp_enabled);
/*
* 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;
mmu->pae_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
if (!mmu->pae_root)
return -ENOMEM;
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;
}
for (i = 0; i < 4; ++i) {
@ -3350,30 +3367,11 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
return -ENOSPC;
mmu->pae_root[i] = root | pm_mask;
}
mmu->root_hpa = __pa(mmu->pae_root);
/*
* When shadowing 32-bit or PAE NPT with 64-bit NPT, the PML4 and PDP
* tables are allocated and initialized at MMU 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. The PDP is
* handled above (to share logic with PAE), deal with the PML4 here.
*/
if (mmu->shadow_root_level == PT64_ROOT_4LEVEL) {
if (mmu->lm_root == NULL) {
u64 *lm_root;
lm_root = (void*)get_zeroed_page(GFP_KERNEL_ACCOUNT);
if (!lm_root)
return -ENOMEM;
lm_root[0] = __pa(mmu->pae_root) | pm_mask;
mmu->lm_root = lm_root;
}
if (mmu->shadow_root_level == PT64_ROOT_4LEVEL)
mmu->root_hpa = __pa(mmu->lm_root);
}
else
mmu->root_hpa = __pa(mmu->pae_root);
set_root_pgd:
mmu->root_pgd = root_pgd;