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kvm: Nested KVM MMUs need PAE root too 

On AMD processors, in PAE 32bit mode, nested KVM instances don't
work. The L0 host get a kernel OOPS, which is related to
arch.mmu->pae_root being NULL.

The reason for this is that when setting up nested KVM instance,
arch.mmu is set to &arch.guest_mmu (while normally, it would be
&arch.root_mmu). However, the initialization and allocation of
pae_root only creates it in root_mmu. KVM code (ie. in
mmu_alloc_shadow_roots) then accesses arch.mmu->pae_root, which is the
unallocated arch.guest_mmu->pae_root.

This fix just allocates (and frees) pae_root in both guest_mmu and
root_mmu (and also lm_root if it was allocated). The allocation is
subject to previous restrictions ie. it won't allocate anything on
64-bit and AFAIK not on Intel.

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=203923
Fixes: 14c07ad89f ("x86/kvm/mmu: introduce guest_mmu")
Signed-off-by: Jiri Palecek <jpalecek@web.de>
Tested-by: Jiri Palecek <jpalecek@web.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
alistair/sunxi64-5.4-dsi
Jiří Paleček 2019-06-22 19:42:04 +02:00 committed by Paolo Bonzini
parent c8848cee74
commit 1cfff4d9a5
1 changed files with 22 additions and 8 deletions
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30
arch/x86/kvm/mmu.c
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@ -5595,13 +5595,13 @@ slot_handle_leaf(struct kvm *kvm, struct kvm_memory_slot *memslot,
PT_PAGE_TABLE_LEVEL, lock_flush_tlb);
}
static void free_mmu_pages(struct kvm_vcpu *vcpu)
static void free_mmu_pages(struct kvm_mmu *mmu)
{
free_page((unsigned long)vcpu->arch.mmu->pae_root);
free_page((unsigned long)vcpu->arch.mmu->lm_root);
free_page((unsigned long)mmu->pae_root);
free_page((unsigned long)mmu->lm_root);
}
static int alloc_mmu_pages(struct kvm_vcpu *vcpu)
static int alloc_mmu_pages(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
{
struct page *page;
int i;
@ -5622,9 +5622,9 @@ static int alloc_mmu_pages(struct kvm_vcpu *vcpu)
if (!page)
return -ENOMEM;
vcpu->arch.mmu->pae_root = page_address(page);
mmu->pae_root = page_address(page);
for (i = 0; i < 4; ++i)
vcpu->arch.mmu->pae_root[i] = INVALID_PAGE;
mmu->pae_root[i] = INVALID_PAGE;
return 0;
}
@ -5632,6 +5632,7 @@ static int alloc_mmu_pages(struct kvm_vcpu *vcpu)
int kvm_mmu_create(struct kvm_vcpu *vcpu)
{
uint i;
int ret;
vcpu->arch.mmu = &vcpu->arch.root_mmu;
vcpu->arch.walk_mmu = &vcpu->arch.root_mmu;
@ -5649,7 +5650,19 @@ int kvm_mmu_create(struct kvm_vcpu *vcpu)
vcpu->arch.guest_mmu.prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID;
vcpu->arch.nested_mmu.translate_gpa = translate_nested_gpa;
return alloc_mmu_pages(vcpu);
ret = alloc_mmu_pages(vcpu, &vcpu->arch.guest_mmu);
if (ret)
return ret;
ret = alloc_mmu_pages(vcpu, &vcpu->arch.root_mmu);
if (ret)
goto fail_allocate_root;
return ret;
fail_allocate_root:
free_mmu_pages(&vcpu->arch.guest_mmu);
return ret;
}
static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
@ -6074,7 +6087,8 @@ unsigned long kvm_mmu_calculate_default_mmu_pages(struct kvm *kvm)
void kvm_mmu_destroy(struct kvm_vcpu *vcpu)
{
kvm_mmu_unload(vcpu);
free_mmu_pages(vcpu);
free_mmu_pages(&vcpu->arch.root_mmu);
free_mmu_pages(&vcpu->arch.guest_mmu);
mmu_free_memory_caches(vcpu);
}