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Commit 374cbac0 authored by Avi Kivity's avatar Avi Kivity Committed by Linus Torvalds
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[PATCH] KVM: MMU: Write protect guest pages when a shadow is created for them 



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: default avatarAvi Kivity <avi@qumranet.com>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent cea0f0e7

drivers/kvm/mmu.c

+54 −18
Original line number Diff line number Diff line
@@ -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);

	paddr = gpa_to_hpa(vcpu, gaddr & PT64_BASE_ADDR_MASK);



	*shadow_pte |= access_bits;



	paddr = gpa_to_hpa(vcpu, gaddr & PT64_BASE_ADDR_MASK);



	if (!(*shadow_pte & PT_GLOBAL_MASK))

		mark_pagetable_nonglobal(shadow_pte);
@@ -752,12 +771,29 @@ 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,

			      u64 addr,

drivers/kvm/paging_tmpl.h

+1 −0
Original line number Diff line number Diff line
@@ -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)