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[PATCH] KVM: MMU: Write protect guest pages when a shadow is created for them

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When we cache a guest page table into a shadow page table, we need to prevent
further access to that page by the guest, as that would render the cache
incoherent.

Signed-off-by: Avi Kivity <avi@qumranet.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Avi Kivity 2007-01-05 16:36:43 -08:00 committed by Linus Torvalds
parent cea0f0e7ea
commit 374cbac033
2 changed files with 56 additions and 19 deletions
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70
drivers/kvm/mmu.c
View File

@ -274,6 +274,35 @@ static void rmap_remove(struct kvm *kvm, u64 *spte)
}
}
static void rmap_write_protect(struct kvm *kvm, u64 gfn)
{
struct page *page;
struct kvm_memory_slot *slot;
struct kvm_rmap_desc *desc;
u64 *spte;
slot = gfn_to_memslot(kvm, gfn);
BUG_ON(!slot);
page = gfn_to_page(slot, gfn);
while (page->private) {
if (!(page->private & 1))
spte = (u64 *)page->private;
else {
desc = (struct kvm_rmap_desc *)(page->private & ~1ul);
spte = desc->shadow_ptes[0];
}
BUG_ON(!spte);
BUG_ON((*spte & PT64_BASE_ADDR_MASK) !=
page_to_pfn(page) << PAGE_SHIFT);
BUG_ON(!(*spte & PT_PRESENT_MASK));
BUG_ON(!(*spte & PT_WRITABLE_MASK));
rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);
rmap_remove(kvm, spte);
*spte &= ~(u64)PT_WRITABLE_MASK;
}
}
static void kvm_mmu_free_page(struct kvm_vcpu *vcpu, hpa_t page_hpa)
{
struct kvm_mmu_page *page_head = page_header(page_hpa);
@ -444,6 +473,8 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
page->gfn = gfn;
page->role = role;
hlist_add_head(&page->hash_link, bucket);
if (!metaphysical)
rmap_write_protect(vcpu->kvm, gfn);
return page;
}
@ -705,6 +736,7 @@ static void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu)
static void paging_new_cr3(struct kvm_vcpu *vcpu)
{
pgprintk("%s: cr3 %lx\n", __FUNCTION__, vcpu->cr3);
mmu_free_roots(vcpu);
mmu_alloc_roots(vcpu);
kvm_mmu_flush_tlb(vcpu);
@ -727,24 +759,11 @@ static inline void set_pte_common(struct kvm_vcpu *vcpu,
*shadow_pte |= access_bits << PT_SHADOW_BITS_OFFSET;
if (!dirty)
access_bits &= ~PT_WRITABLE_MASK;
if (access_bits & PT_WRITABLE_MASK) {
struct kvm_mmu_page *shadow;
shadow = kvm_mmu_lookup_page(vcpu, gaddr >> PAGE_SHIFT);
if (shadow)
pgprintk("%s: found shadow page for %lx, marking ro\n",
__FUNCTION__, (gfn_t)(gaddr >> PAGE_SHIFT));
if (shadow)
access_bits &= ~PT_WRITABLE_MASK;
}
if (access_bits & PT_WRITABLE_MASK)
mark_page_dirty(vcpu->kvm, gaddr >> PAGE_SHIFT);
*shadow_pte |= access_bits;
paddr = gpa_to_hpa(vcpu, gaddr & PT64_BASE_ADDR_MASK);
*shadow_pte |= access_bits;
if (!(*shadow_pte & PT_GLOBAL_MASK))
mark_pagetable_nonglobal(shadow_pte);
@ -752,11 +771,28 @@ static inline void set_pte_common(struct kvm_vcpu *vcpu,
*shadow_pte |= gaddr;
*shadow_pte |= PT_SHADOW_IO_MARK;
*shadow_pte &= ~PT_PRESENT_MASK;
} else {
return;
}
*shadow_pte |= paddr;
if (access_bits & PT_WRITABLE_MASK) {
struct kvm_mmu_page *shadow;
shadow = kvm_mmu_lookup_page(vcpu, gaddr >> PAGE_SHIFT);
if (shadow) {
pgprintk("%s: found shadow page for %lx, marking ro\n",
__FUNCTION__, (gfn_t)(gaddr >> PAGE_SHIFT));
access_bits &= ~PT_WRITABLE_MASK;
*shadow_pte &= ~PT_WRITABLE_MASK;
}
}
if (access_bits & PT_WRITABLE_MASK)
mark_page_dirty(vcpu->kvm, gaddr >> PAGE_SHIFT);
page_header_update_slot(vcpu->kvm, shadow_pte, gaddr);
rmap_add(vcpu->kvm, shadow_pte);
}
}
static void inject_page_fault(struct kvm_vcpu *vcpu,

1
drivers/kvm/paging_tmpl.h
View File

@ -133,6 +133,7 @@ static void FNAME(walk_addr)(struct guest_walker *walker,
walker->level - 1, table_gfn);
}
walker->ptep = ptep;
pgprintk("%s: pte %llx\n", __FUNCTION__, (u64)*ptep);
}
static void FNAME(release_walker)(struct guest_walker *walker)