Commit 53597858 authored by David Matlack's avatar David Matlack Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: Avoid memslot lookup in make_spte and mmu_try_to_unsync_pages 



mmu_try_to_unsync_pages checks if page tracking is active for the given
gfn, which requires knowing the memslot. We can pass down the memslot
via make_spte to avoid this lookup.

The memslot is also handy for make_spte's marking of the gfn as dirty:
we can test whether dirty page tracking is enabled, and if so ensure that
pages are mapped as writable with 4K granularity.  Apart from the warning,
no functional change is intended.

Signed-off-by: default avatarDavid Matlack <dmatlack@google.com>
Message-Id: <20210813203504.2742757-7-dmatlack@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 8a9f566a

arch/x86/include/asm/kvm_page_track.h

+0 −2
Original line number Diff line number Diff line
@@ -59,8 +59,6 @@ void kvm_slot_page_track_add_page(struct kvm *kvm, 
void kvm_slot_page_track_remove_page(struct kvm *kvm,

				     struct kvm_memory_slot *slot, gfn_t gfn,

				     enum kvm_page_track_mode mode);

bool kvm_page_track_is_active(struct kvm_vcpu *vcpu, gfn_t gfn,

			      enum kvm_page_track_mode mode);

bool kvm_slot_page_track_is_active(struct kvm_memory_slot *slot, gfn_t gfn,

				   enum kvm_page_track_mode mode);

arch/x86/kvm/mmu/mmu.c

+4 −4
Original line number Diff line number Diff line
@@ -2572,8 +2572,8 @@ static void kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 
 * were marked unsync (or if there is no shadow page), -EPERM if the SPTE must

 * be write-protected.

 */

int mmu_try_to_unsync_pages(struct kvm_vcpu *vcpu, gfn_t gfn, bool can_unsync,

			    bool speculative)

int mmu_try_to_unsync_pages(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot,

			    gfn_t gfn, bool can_unsync, bool speculative)

{

	struct kvm_mmu_page *sp;

	bool locked = false;
@@ -2583,7 +2583,7 @@ int mmu_try_to_unsync_pages(struct kvm_vcpu *vcpu, gfn_t gfn, bool can_unsync, 
	 * track machinery is used to write-protect upper-level shadow pages,

	 * i.e. this guards the role.level == 4K assertion below!

	 */

	if (kvm_page_track_is_active(vcpu, gfn, KVM_PAGE_TRACK_WRITE))

	if (kvm_slot_page_track_is_active(slot, gfn, KVM_PAGE_TRACK_WRITE))

		return -EPERM;



	/*
@@ -2719,7 +2719,7 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot, 
			was_rmapped = 1;

	}



	wrprot = make_spte(vcpu, sp, pte_access, gfn, pfn, *sptep, speculative,

	wrprot = make_spte(vcpu, sp, slot, pte_access, gfn, pfn, *sptep, speculative,

			   true, host_writable, &spte);



	if (*sptep == spte) {

arch/x86/kvm/mmu/mmu_internal.h

+2 −2
Original line number Diff line number Diff line
@@ -118,8 +118,8 @@ static inline bool kvm_vcpu_ad_need_write_protect(struct kvm_vcpu *vcpu) 
	       kvm_x86_ops.cpu_dirty_log_size;

}



int mmu_try_to_unsync_pages(struct kvm_vcpu *vcpu, gfn_t gfn, bool can_unsync,

			    bool speculative);

int mmu_try_to_unsync_pages(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot,

			    gfn_t gfn, bool can_unsync, bool speculative);



void kvm_mmu_gfn_disallow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn);

void kvm_mmu_gfn_allow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn);

arch/x86/kvm/mmu/page_track.c

+3 −11
Original line number Diff line number Diff line
@@ -136,6 +136,9 @@ void kvm_slot_page_track_remove_page(struct kvm *kvm, 
}

EXPORT_SYMBOL_GPL(kvm_slot_page_track_remove_page);



/*

 * check if the corresponding access on the specified guest page is tracked.

 */

bool kvm_slot_page_track_is_active(struct kvm_memory_slot *slot, gfn_t gfn,

				   enum kvm_page_track_mode mode)

{
@@ -151,17 +154,6 @@ bool kvm_slot_page_track_is_active(struct kvm_memory_slot *slot, gfn_t gfn, 
	return !!READ_ONCE(slot->arch.gfn_track[mode][index]);

}



/*

 * check if the corresponding access on the specified guest page is tracked.

 */

bool kvm_page_track_is_active(struct kvm_vcpu *vcpu, gfn_t gfn,

			      enum kvm_page_track_mode mode)

{

	struct kvm_memory_slot *slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);



	return kvm_slot_page_track_is_active(slot, gfn, mode);

}



void kvm_page_track_cleanup(struct kvm *kvm)

{

	struct kvm_page_track_notifier_head *head;

arch/x86/kvm/mmu/paging_tmpl.h

+3 −1
Original line number Diff line number Diff line
@@ -1091,6 +1091,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 


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

		u64 *sptep, spte;

		struct kvm_memory_slot *slot;

		unsigned pte_access;

		pt_element_t gpte;

		gpa_t pte_gpa;
@@ -1127,7 +1128,8 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 
		sptep = &sp->spt[i];

		spte = *sptep;

		host_writable = spte & shadow_host_writable_mask;

		make_spte(vcpu, sp, pte_access, gfn,

		slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);

		make_spte(vcpu, sp, slot, pte_access, gfn,

			  spte_to_pfn(spte), spte, true, false,

			  host_writable, &spte);