Commit 9647c14c authored by Izik Eidus's avatar Izik Eidus Committed by Avi Kivity
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KVM: MMU: Keep a reverse mapping of non-writable translations 



The current kvm mmu only reverse maps writable translation.  This is used
to write-protect a page in case it becomes a pagetable.

But with swapping support, we need a reverse mapping of read-only pages as
well:  when we evict a page, we need to remove any mapping to it, whether
writable or not.

Signed-off-by: default avatarIzik Eidus <izike@qumranet.com>
Signed-off-by: default avatarAvi Kivity <avi@qumranet.com>
parent 98348e95

drivers/kvm/mmu.c

+11 −12
Original line number Diff line number Diff line
@@ -211,8 +211,8 @@ static int is_io_pte(unsigned long pte) 


static int is_rmap_pte(u64 pte)

{

	return (pte & (PT_WRITABLE_MASK | PT_PRESENT_MASK))

		== (PT_WRITABLE_MASK | PT_PRESENT_MASK);

	return pte != shadow_trap_nonpresent_pte

		&& pte != shadow_notrap_nonpresent_pte;

}



static void set_shadow_pte(u64 *sptep, u64 spte)
@@ -488,7 +488,6 @@ static void rmap_write_protect(struct kvm *kvm, u64 gfn) 
{

	unsigned long *rmapp;

	u64 *spte;

	u64 *prev_spte;



	gfn = unalias_gfn(kvm, gfn);

	rmapp = gfn_to_rmap(kvm, gfn);
@@ -497,13 +496,11 @@ static void rmap_write_protect(struct kvm *kvm, u64 gfn) 
	while (spte) {

		BUG_ON(!spte);

		BUG_ON(!(*spte & PT_PRESENT_MASK));

		BUG_ON(!(*spte & PT_WRITABLE_MASK));

		rmap_printk("rmap_write_protect: spte %p %llx\n", spte, *spte);

		prev_spte = spte;

		spte = rmap_next(kvm, rmapp, spte);

		rmap_remove(kvm, prev_spte);

		set_shadow_pte(prev_spte, *prev_spte & ~PT_WRITABLE_MASK);

		if (is_writeble_pte(*spte))

			set_shadow_pte(spte, *spte & ~PT_WRITABLE_MASK);

		kvm_flush_remote_tlbs(kvm);

		spte = rmap_next(kvm, rmapp, spte);

	}

}
@@ -908,13 +905,17 @@ static int nonpaging_map(struct kvm_vcpu *vcpu, gva_t v, hpa_t p) 
		table = __va(table_addr);



		if (level == 1) {

			int was_rmapped;



			pte = table[index];

			was_rmapped = is_rmap_pte(pte);

			if (is_shadow_present_pte(pte) && is_writeble_pte(pte))

				return 0;

			mark_page_dirty(vcpu->kvm, v >> PAGE_SHIFT);

			page_header_update_slot(vcpu->kvm, table, v);

			table[index] = p | PT_PRESENT_MASK | PT_WRITABLE_MASK |

								PT_USER_MASK;

			if (!was_rmapped)

				rmap_add(vcpu, &table[index], v >> PAGE_SHIFT);

			return 0;

		}
@@ -1424,12 +1425,10 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot) 
		pt = page->spt;

		for (i = 0; i < PT64_ENT_PER_PAGE; ++i)

			/* avoid RMW */

			if (pt[i] & PT_WRITABLE_MASK) {

				rmap_remove(kvm, &pt[i]);

			if (pt[i] & PT_WRITABLE_MASK)

				pt[i] &= ~PT_WRITABLE_MASK;

	}

}

}



void kvm_mmu_zap_all(struct kvm *kvm)

{