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Commit f39a058d authored by Junaid Shahid's avatar Junaid Shahid Committed by Radim Krčmář
Browse files

kvm: x86: mmu: Introduce a no-tracking version of mmu_spte_update 



mmu_spte_update() tracks changes in the accessed/dirty state of
the SPTE being updated and calls kvm_set_pfn_accessed/dirty
appropriately. However, in some cases (e.g. when aging the SPTE),
this shouldn't be done. mmu_spte_update_no_track() is introduced
for use in such cases.

Signed-off-by: default avatarJunaid Shahid <junaids@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 83ef6c81

arch/x86/kvm/mmu.c

+27 −13
Original line number Diff line number Diff line
@@ -528,27 +528,19 @@ static void mmu_spte_set(u64 *sptep, u64 new_spte) 
	__set_spte(sptep, new_spte);

}



/* Rules for using mmu_spte_update:

 * Update the state bits, it means the mapped pfn is not changed.

 *

 * Whenever we overwrite a writable spte with a read-only one we

 * should flush remote TLBs. Otherwise rmap_write_protect

 * will find a read-only spte, even though the writable spte

 * might be cached on a CPU's TLB, the return value indicates this

 * case.

 *

 * Returns true if the TLB needs to be flushed

/*

 * Update the SPTE (excluding the PFN), but do not track changes in its

 * accessed/dirty status.

 */

static bool mmu_spte_update(u64 *sptep, u64 new_spte)

static u64 mmu_spte_update_no_track(u64 *sptep, u64 new_spte)

{

	u64 old_spte = *sptep;

	bool flush = false;



	WARN_ON(!is_shadow_present_pte(new_spte));



	if (!is_shadow_present_pte(old_spte)) {

		mmu_spte_set(sptep, new_spte);

		return flush;

		return old_spte;

	}



	if (!spte_has_volatile_bits(old_spte))
@@ -558,6 +550,28 @@ static bool mmu_spte_update(u64 *sptep, u64 new_spte) 


	WARN_ON(spte_to_pfn(old_spte) != spte_to_pfn(new_spte));



	return old_spte;

}



/* Rules for using mmu_spte_update:

 * Update the state bits, it means the mapped pfn is not changed.

 *

 * Whenever we overwrite a writable spte with a read-only one we

 * should flush remote TLBs. Otherwise rmap_write_protect

 * will find a read-only spte, even though the writable spte

 * might be cached on a CPU's TLB, the return value indicates this

 * case.

 *

 * Returns true if the TLB needs to be flushed

 */

static bool mmu_spte_update(u64 *sptep, u64 new_spte)

{

	bool flush = false;

	u64 old_spte = mmu_spte_update_no_track(sptep, new_spte);



	if (!is_shadow_present_pte(old_spte))

		return false;



	/*

	 * For the spte updated out of mmu-lock is safe, since

	 * we always atomically update it, see the comments in