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Commit 61719a8f authored by Gleb Natapov's avatar Gleb Natapov Committed by Paolo Bonzini
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nEPT: Support shadow paging for guest paging without A/D bits 



Some guest paging modes do not support A/D bits. Add support for such
modes in shadow page code. For such modes PT_GUEST_DIRTY_MASK,
PT_GUEST_ACCESSED_MASK, PT_GUEST_DIRTY_SHIFT and PT_GUEST_ACCESSED_SHIFT
should be set to zero.

Reviewed-by: default avatarXiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent d8089bac

arch/x86/kvm/paging_tmpl.h

+13 −3
Original line number Diff line number Diff line
@@ -92,6 +92,10 @@ static inline void FNAME(protect_clean_gpte)(unsigned *access, unsigned gpte) 
{

	unsigned mask;



	/* dirty bit is not supported, so no need to track it */

	if (!PT_GUEST_DIRTY_MASK)

		return;



	BUILD_BUG_ON(PT_WRITABLE_MASK != ACC_WRITE_MASK);



	mask = (unsigned)~ACC_WRITE_MASK;
@@ -147,7 +151,8 @@ static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu, 
	if (!FNAME(is_present_gpte)(gpte))

		goto no_present;



	if (!(gpte & PT_GUEST_ACCESSED_MASK))

	/* if accessed bit is not supported prefetch non accessed gpte */

	if (PT_GUEST_ACCESSED_MASK && !(gpte & PT_GUEST_ACCESSED_MASK))

		goto no_present;



	return false;
@@ -178,6 +183,10 @@ static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu, 
	gfn_t table_gfn;

	int ret;



	/* dirty/accessed bits are not supported, so no need to update them */

	if (!PT_GUEST_DIRTY_MASK)

		return 0;



	for (level = walker->max_level; level >= walker->level; --level) {

		pte = orig_pte = walker->ptes[level - 1];

		table_gfn = walker->table_gfn[level - 1];
@@ -316,8 +325,9 @@ retry_walk: 
		FNAME(protect_clean_gpte)(&pte_access, pte);

	else

		/*

		 * On a write fault, fold the dirty bit into accessed_dirty by

		 * shifting it one place right.

		 * On a write fault, fold the dirty bit into accessed_dirty.

		 * For modes without A/D bits support accessed_dirty will be

		 * always clear.

		 */

		accessed_dirty &= pte >>

			(PT_GUEST_DIRTY_SHIFT - PT_GUEST_ACCESSED_SHIFT);