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Subject[PATCH 22/27] KVM: MMU: Refactor mmu_alloc_roots function
Date
This patch factors out the direct-mapping paths of the
mmu_alloc_roots function into a seperate function. This
makes it a lot easier to avoid all the unnecessary checks
done in the shadow path which may break when running direct.
In fact, this patch already fixes a problem when running PAE
guests on a PAE shadow page table.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
---
arch/x86/kvm/mmu.c | 82 ++++++++++++++++++++++++++++++++++++++--------------
1 files changed, 60 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 3663d1c..e7e5527 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2357,42 +2357,77 @@ static int mmu_check_root(struct kvm_vcpu *vcpu, gfn_t root_gfn)
return ret;
}

-static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
+static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
+{
+ struct kvm_mmu_page *sp;
+ int i;
+
+ if (vcpu->arch.mmu.shadow_root_level == PT64_ROOT_LEVEL) {
+ spin_lock(&vcpu->kvm->mmu_lock);
+ kvm_mmu_free_some_pages(vcpu);
+ sp = kvm_mmu_get_page(vcpu, 0, 0, PT64_ROOT_LEVEL,
+ 1, ACC_ALL, NULL);
+ ++sp->root_count;
+ spin_unlock(&vcpu->kvm->mmu_lock);
+ vcpu->arch.mmu.root_hpa = __pa(sp->spt);
+ } else if (vcpu->arch.mmu.shadow_root_level == PT32E_ROOT_LEVEL) {
+ for (i = 0; i < 4; ++i) {
+ hpa_t root = vcpu->arch.mmu.pae_root[i];
+
+ ASSERT(!VALID_PAGE(root));
+ spin_lock(&vcpu->kvm->mmu_lock);
+ kvm_mmu_free_some_pages(vcpu);
+ sp = kvm_mmu_get_page(vcpu, i << 30, i << 30,
+ PT32_ROOT_LEVEL, 1, ACC_ALL,
+ NULL);
+ root = __pa(sp->spt);
+ ++sp->root_count;
+ spin_unlock(&vcpu->kvm->mmu_lock);
+ vcpu->arch.mmu.pae_root[i] = root | PT_PRESENT_MASK;
+ vcpu->arch.mmu.root_hpa = __pa(vcpu->arch.mmu.pae_root);
+ }
+ } else
+ BUG();
+
+ return 0;
+}
+
+static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
{
int i;
gfn_t root_gfn;
struct kvm_mmu_page *sp;
- int direct = 0;
u64 pdptr;

root_gfn = vcpu->arch.mmu.get_cr3(vcpu) >> PAGE_SHIFT;

- if (vcpu->arch.mmu.shadow_root_level == PT64_ROOT_LEVEL) {
+ if (mmu_check_root(vcpu, root_gfn))
+ return 1;
+
+ /*
+ * Do we shadow a long mode page table? If so we need to
+ * write-protect the guests page table root.
+ */
+ if (vcpu->arch.mmu.root_level == PT64_ROOT_LEVEL) {
hpa_t root = vcpu->arch.mmu.root_hpa;

ASSERT(!VALID_PAGE(root));
- if (mmu_check_root(vcpu, root_gfn))
- return 1;
- if (vcpu->arch.mmu.direct_map) {
- direct = 1;
- root_gfn = 0;
- }
+
spin_lock(&vcpu->kvm->mmu_lock);
kvm_mmu_free_some_pages(vcpu);
- sp = kvm_mmu_get_page(vcpu, root_gfn, 0,
- PT64_ROOT_LEVEL, direct,
- ACC_ALL, NULL);
+ sp = kvm_mmu_get_page(vcpu, root_gfn, 0, PT64_ROOT_LEVEL,
+ 0, ACC_ALL, NULL);
root = __pa(sp->spt);
++sp->root_count;
spin_unlock(&vcpu->kvm->mmu_lock);
vcpu->arch.mmu.root_hpa = root;
return 0;
}
- direct = !is_paging(vcpu);
-
- if (mmu_check_root(vcpu, root_gfn))
- return 1;

+ /*
+ * We shadow a 32 bit page table. This may be a legacy 2-level
+ * or a PAE 3-level page table.
+ */
for (i = 0; i < 4; ++i) {
hpa_t root = vcpu->arch.mmu.pae_root[i];

@@ -2406,16 +2441,11 @@ static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
root_gfn = pdptr >> PAGE_SHIFT;
if (mmu_check_root(vcpu, root_gfn))
return 1;
- } else if (vcpu->arch.mmu.root_level == 0)
- root_gfn = 0;
- if (vcpu->arch.mmu.direct_map) {
- direct = 1;
- root_gfn = i << 30;
}
spin_lock(&vcpu->kvm->mmu_lock);
kvm_mmu_free_some_pages(vcpu);
sp = kvm_mmu_get_page(vcpu, root_gfn, i << 30,
- PT32_ROOT_LEVEL, direct,
+ PT32_ROOT_LEVEL, 0,
ACC_ALL, NULL);
root = __pa(sp->spt);
++sp->root_count;
@@ -2427,6 +2457,14 @@ static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
return 0;
}

+static int mmu_alloc_roots(struct kvm_vcpu *vcpu)
+{
+ if (vcpu->arch.mmu.direct_map)
+ return mmu_alloc_direct_roots(vcpu);
+ else
+ return mmu_alloc_shadow_roots(vcpu);
+}
+
static void mmu_sync_roots(struct kvm_vcpu *vcpu)
{
int i;
--
1.7.0.4



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