[PATCH 6/33] KVM: MMU: Use the guest pdptrs instead of mapping cr3 in pae mode

Avi Kivity
2007-01-04T15:55:06Z

This lets us not write protect a partial page, and is anyway what a
real processor does.

Signed-off-by: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>

Index: linux-2.6/drivers/kvm/paging_tmpl.h
===================================================================
--- linux-2.6.orig/drivers/kvm/paging_tmpl.h
+++ linux-2.6/drivers/kvm/paging_tmpl.h
@@ -67,18 +67,28 @@ static void FNAME(walk_addr)(struct gues
hpa_t hpa;
struct kvm_memory_slot *slot;
pt_element_t *ptep;
+ pt_element_t root;

walker->level = vcpu->mmu.root_level;
- walker->table_gfn = (vcpu->cr3 & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
+ walker->table = NULL;
+ root = vcpu->cr3;
+#if PTTYPE == 64
+ if (!is_long_mode(vcpu)) {
+ walker->ptep = &vcpu->pdptrs[(addr >> 30) & 3];
+ root = *walker->ptep;
+ if (!(root & PT_PRESENT_MASK))
+ return;
+ --walker->level;
+ }
+#endif
+ walker->table_gfn = (root & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
slot = gfn_to_memslot(vcpu->kvm, walker->table_gfn);
- hpa = safe_gpa_to_hpa(vcpu, vcpu->cr3 & PT64_BASE_ADDR_MASK);
+ hpa = safe_gpa_to_hpa(vcpu, root & PT64_BASE_ADDR_MASK);
walker->table = kmap_atomic(pfn_to_page(hpa >> PAGE_SHIFT), KM_USER0);

ASSERT((!is_long_mode(vcpu) && is_pae(vcpu)) ||
(vcpu->cr3 & ~(PAGE_MASK | CR3_FLAGS_MASK)) == 0);

- walker->table = (pt_element_t *)( (unsigned long)walker->table |
- (unsigned long)(vcpu->cr3 & ~(PAGE_MASK | CR3_FLAGS_MASK)) );
walker->inherited_ar = PT_USER_MASK | PT_WRITABLE_MASK;

for (;;) {
@@ -89,11 +99,8 @@ static void FNAME(walk_addr)(struct gues
ASSERT(((unsigned long)walker->table & PAGE_MASK) ==
((unsigned long)ptep & PAGE_MASK));

- /* Don't set accessed bit on PAE PDPTRs */
- if (vcpu->mmu.root_level != 3 || walker->level != 3)
- if ((*ptep & (PT_PRESENT_MASK | PT_ACCESSED_MASK))
- == PT_PRESENT_MASK)
- *ptep |= PT_ACCESSED_MASK;
+ if (is_present_pte(*ptep) && !(*ptep & PT_ACCESSED_MASK))
+ *ptep |= PT_ACCESSED_MASK;

if (!is_present_pte(*ptep) ||
walker->level == PT_PAGE_TABLE_LEVEL ||
@@ -116,7 +123,8 @@ static void FNAME(walk_addr)(struct gues

static void FNAME(release_walker)(struct guest_walker *walker)
{
- kunmap_atomic(walker->table, KM_USER0);
+ if (walker->table)
+ kunmap_atomic(walker->table, KM_USER0);
}

static void FNAME(set_pte)(struct kvm_vcpu *vcpu, u64 guest_pte,
Index: linux-2.6/drivers/kvm/kvm_main.c
===================================================================
--- linux-2.6.orig/drivers/kvm/kvm_main.c
+++ linux-2.6/drivers/kvm/kvm_main.c
@@ -1491,6 +1491,8 @@ static int kvm_dev_ioctl_set_sregs(struc

mmu_reset_needed |= vcpu->cr4 != sregs->cr4;
kvm_arch_ops->set_cr4(vcpu, sregs->cr4);
+ if (!is_long_mode(vcpu) && is_pae(vcpu))
+ load_pdptrs(vcpu, vcpu->cr3);

if (mmu_reset_needed)
kvm_mmu_reset_context(vcpu);