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Commit c3707958 authored by Xiao Guangrong's avatar Xiao Guangrong Committed by Avi Kivity
Browse files

KVM: MMU: remove bypass_guest_pf 



The idea is from Avi:
| Maybe it's time to kill off bypass_guest_pf=1.  It's not as effective as
| it used to be, since unsync pages always use shadow_trap_nonpresent_pte,
| and since we convert between the two nonpresent_ptes during sync and unsync.

Signed-off-by: default avatarXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent bd4c86ea

Documentation/kernel-parameters.txt

+0 −4
Original line number Diff line number Diff line
@@ -1159,10 +1159,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
			for all guests.

			Default is 1 (enabled) if in 64bit or 32bit-PAE mode



	kvm-intel.bypass_guest_pf=

			[KVM,Intel] Disables bypassing of guest page faults

			on Intel chips. Default is 1 (enabled)



	kvm-intel.ept=	[KVM,Intel] Disable extended page tables

			(virtualized MMU) support on capable Intel chips.

			Default is 1 (enabled)

arch/x86/include/asm/kvm_host.h

+0 −3
Original line number Diff line number Diff line
@@ -266,8 +266,6 @@ struct kvm_mmu { 
	gpa_t (*gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t gva, u32 access,

			    struct x86_exception *exception);

	gpa_t (*translate_gpa)(struct kvm_vcpu *vcpu, gpa_t gpa, u32 access);

	void (*prefetch_page)(struct kvm_vcpu *vcpu,

			      struct kvm_mmu_page *page);

	int (*sync_page)(struct kvm_vcpu *vcpu,

			 struct kvm_mmu_page *sp);

	void (*invlpg)(struct kvm_vcpu *vcpu, gva_t gva);
@@ -647,7 +645,6 @@ void kvm_mmu_module_exit(void); 
void kvm_mmu_destroy(struct kvm_vcpu *vcpu);

int kvm_mmu_create(struct kvm_vcpu *vcpu);

int kvm_mmu_setup(struct kvm_vcpu *vcpu);

void kvm_mmu_set_nonpresent_ptes(u64 trap_pte, u64 notrap_pte);

void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask,

		u64 dirty_mask, u64 nx_mask, u64 x_mask);

arch/x86/kvm/mmu.c

+24 −59
Original line number Diff line number Diff line
@@ -186,8 +186,6 @@ static struct kmem_cache *pte_list_desc_cache; 
static struct kmem_cache *mmu_page_header_cache;

static struct percpu_counter kvm_total_used_mmu_pages;



static u64 __read_mostly shadow_trap_nonpresent_pte;

static u64 __read_mostly shadow_notrap_nonpresent_pte;

static u64 __read_mostly shadow_nx_mask;

static u64 __read_mostly shadow_x_mask;	/* mutual exclusive with nx_mask */

static u64 __read_mostly shadow_user_mask;
@@ -199,13 +197,6 @@ static inline u64 rsvd_bits(int s, int e) 
	return ((1ULL << (e - s + 1)) - 1) << s;

}



void kvm_mmu_set_nonpresent_ptes(u64 trap_pte, u64 notrap_pte)

{

	shadow_trap_nonpresent_pte = trap_pte;

	shadow_notrap_nonpresent_pte = notrap_pte;

}

EXPORT_SYMBOL_GPL(kvm_mmu_set_nonpresent_ptes);



void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask,

		u64 dirty_mask, u64 nx_mask, u64 x_mask)

{
@@ -229,8 +220,7 @@ static int is_nx(struct kvm_vcpu *vcpu) 


static int is_shadow_present_pte(u64 pte)

{

	return pte != shadow_trap_nonpresent_pte

		&& pte != shadow_notrap_nonpresent_pte;

	return pte & PT_PRESENT_MASK;

}



static int is_large_pte(u64 pte)
@@ -777,9 +767,9 @@ static int set_spte_track_bits(u64 *sptep, u64 new_spte) 
	return 1;

}



static void drop_spte(struct kvm *kvm, u64 *sptep, u64 new_spte)

static void drop_spte(struct kvm *kvm, u64 *sptep)

{

	if (set_spte_track_bits(sptep, new_spte))

	if (set_spte_track_bits(sptep, 0ull))

		rmap_remove(kvm, sptep);

}
@@ -814,8 +804,7 @@ static int rmap_write_protect(struct kvm *kvm, u64 gfn) 
			BUG_ON((*spte & (PT_PAGE_SIZE_MASK|PT_PRESENT_MASK)) != (PT_PAGE_SIZE_MASK|PT_PRESENT_MASK));

			pgprintk("rmap_write_protect(large): spte %p %llx %lld\n", spte, *spte, gfn);

			if (is_writable_pte(*spte)) {

				drop_spte(kvm, spte,

					  shadow_trap_nonpresent_pte);

				drop_spte(kvm, spte);

				--kvm->stat.lpages;

				spte = NULL;

				write_protected = 1;
@@ -836,7 +825,7 @@ static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp, 
	while ((spte = rmap_next(kvm, rmapp, NULL))) {

		BUG_ON(!(*spte & PT_PRESENT_MASK));

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

		drop_spte(kvm, spte, shadow_trap_nonpresent_pte);

		drop_spte(kvm, spte);

		need_tlb_flush = 1;

	}

	return need_tlb_flush;
@@ -858,7 +847,7 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, unsigned long *rmapp, 
		rmap_printk("kvm_set_pte_rmapp: spte %p %llx\n", spte, *spte);

		need_flush = 1;

		if (pte_write(*ptep)) {

			drop_spte(kvm, spte, shadow_trap_nonpresent_pte);

			drop_spte(kvm, spte);

			spte = rmap_next(kvm, rmapp, NULL);

		} else {

			new_spte = *spte &~ (PT64_BASE_ADDR_MASK);
@@ -1088,7 +1077,7 @@ static void drop_parent_pte(struct kvm_mmu_page *sp, 
			    u64 *parent_pte)

{

	mmu_page_remove_parent_pte(sp, parent_pte);

	__set_spte(parent_pte, shadow_trap_nonpresent_pte);

	__set_spte(parent_pte, 0ull);

}



static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
@@ -1130,15 +1119,6 @@ static void mark_unsync(u64 *spte) 
	kvm_mmu_mark_parents_unsync(sp);

}



static void nonpaging_prefetch_page(struct kvm_vcpu *vcpu,

				    struct kvm_mmu_page *sp)

{

	int i;



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

		sp->spt[i] = shadow_trap_nonpresent_pte;

}



static int nonpaging_sync_page(struct kvm_vcpu *vcpu,

			       struct kvm_mmu_page *sp)

{
@@ -1420,6 +1400,14 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu, 
	}

}



static void init_shadow_page_table(struct kvm_mmu_page *sp)

{

	int i;



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

		sp->spt[i] = 0ull;

}



static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,

					     gfn_t gfn,

					     gva_t gaddr,
@@ -1482,10 +1470,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, 


		account_shadowed(vcpu->kvm, gfn);

	}

	if (shadow_trap_nonpresent_pte != shadow_notrap_nonpresent_pte)

		vcpu->arch.mmu.prefetch_page(vcpu, sp);

	else

		nonpaging_prefetch_page(vcpu, sp);

	init_shadow_page_table(sp);

	trace_kvm_mmu_get_page(sp, true);

	return sp;

}
@@ -1546,7 +1531,7 @@ static void link_shadow_page(u64 *sptep, struct kvm_mmu_page *sp) 
static void drop_large_spte(struct kvm_vcpu *vcpu, u64 *sptep)

{

	if (is_large_pte(*sptep)) {

		drop_spte(vcpu->kvm, sptep, shadow_trap_nonpresent_pte);

		drop_spte(vcpu->kvm, sptep);

		kvm_flush_remote_tlbs(vcpu->kvm);

	}

}
@@ -1582,13 +1567,13 @@ static void mmu_page_zap_pte(struct kvm *kvm, struct kvm_mmu_page *sp, 
	pte = *spte;

	if (is_shadow_present_pte(pte)) {

		if (is_last_spte(pte, sp->role.level))

			drop_spte(kvm, spte, shadow_trap_nonpresent_pte);

			drop_spte(kvm, spte);

		else {

			child = page_header(pte & PT64_BASE_ADDR_MASK);

			drop_parent_pte(child, spte);

		}

	}

	__set_spte(spte, shadow_trap_nonpresent_pte);



	if (is_large_pte(pte))

		--kvm->stat.lpages;

}
@@ -1769,20 +1754,6 @@ static void page_header_update_slot(struct kvm *kvm, void *pte, gfn_t gfn) 
	__set_bit(slot, sp->slot_bitmap);

}



static void mmu_convert_notrap(struct kvm_mmu_page *sp)

{

	int i;

	u64 *pt = sp->spt;



	if (shadow_trap_nonpresent_pte == shadow_notrap_nonpresent_pte)

		return;



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

		if (pt[i] == shadow_notrap_nonpresent_pte)

			__set_spte(&pt[i], shadow_trap_nonpresent_pte);

	}

}



/*

 * The function is based on mtrr_type_lookup() in

 * arch/x86/kernel/cpu/mtrr/generic.c
@@ -1895,7 +1866,6 @@ static void __kvm_unsync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 
	sp->unsync = 1;



	kvm_mmu_mark_parents_unsync(sp);

	mmu_convert_notrap(sp);

}



static void kvm_unsync_pages(struct kvm_vcpu *vcpu,  gfn_t gfn)
@@ -1980,7 +1950,7 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, 
		if (level > PT_PAGE_TABLE_LEVEL &&

		    has_wrprotected_page(vcpu->kvm, gfn, level)) {

			ret = 1;

			drop_spte(vcpu->kvm, sptep, shadow_trap_nonpresent_pte);

			drop_spte(vcpu->kvm, sptep);

			goto done;

		}
@@ -2066,7 +2036,7 @@ static void mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, 
		} else if (pfn != spte_to_pfn(*sptep)) {

			pgprintk("hfn old %llx new %llx\n",

				 spte_to_pfn(*sptep), pfn);

			drop_spte(vcpu->kvm, sptep, shadow_trap_nonpresent_pte);

			drop_spte(vcpu->kvm, sptep);

			kvm_flush_remote_tlbs(vcpu->kvm);

		} else

			was_rmapped = 1;
@@ -2162,7 +2132,7 @@ static void __direct_pte_prefetch(struct kvm_vcpu *vcpu, 
	spte = sp->spt + i;



	for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) {

		if (*spte != shadow_trap_nonpresent_pte || spte == sptep) {

		if (is_shadow_present_pte(*spte) || spte == sptep) {

			if (!start)

				continue;

			if (direct_pte_prefetch_many(vcpu, sp, start, spte) < 0)
@@ -2214,7 +2184,7 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write, 
			break;

		}



		if (*iterator.sptep == shadow_trap_nonpresent_pte) {

		if (!is_shadow_present_pte(*iterator.sptep)) {

			u64 base_addr = iterator.addr;



			base_addr &= PT64_LVL_ADDR_MASK(iterator.level);
@@ -2748,7 +2718,6 @@ static int nonpaging_init_context(struct kvm_vcpu *vcpu, 
	context->page_fault = nonpaging_page_fault;

	context->gva_to_gpa = nonpaging_gva_to_gpa;

	context->free = nonpaging_free;

	context->prefetch_page = nonpaging_prefetch_page;

	context->sync_page = nonpaging_sync_page;

	context->invlpg = nonpaging_invlpg;

	context->update_pte = nonpaging_update_pte;
@@ -2878,7 +2847,6 @@ static int paging64_init_context_common(struct kvm_vcpu *vcpu, 
	context->new_cr3 = paging_new_cr3;

	context->page_fault = paging64_page_fault;

	context->gva_to_gpa = paging64_gva_to_gpa;

	context->prefetch_page = paging64_prefetch_page;

	context->sync_page = paging64_sync_page;

	context->invlpg = paging64_invlpg;

	context->update_pte = paging64_update_pte;
@@ -2907,7 +2875,6 @@ static int paging32_init_context(struct kvm_vcpu *vcpu, 
	context->page_fault = paging32_page_fault;

	context->gva_to_gpa = paging32_gva_to_gpa;

	context->free = paging_free;

	context->prefetch_page = paging32_prefetch_page;

	context->sync_page = paging32_sync_page;

	context->invlpg = paging32_invlpg;

	context->update_pte = paging32_update_pte;
@@ -2932,7 +2899,6 @@ static int init_kvm_tdp_mmu(struct kvm_vcpu *vcpu) 
	context->new_cr3 = nonpaging_new_cr3;

	context->page_fault = tdp_page_fault;

	context->free = nonpaging_free;

	context->prefetch_page = nonpaging_prefetch_page;

	context->sync_page = nonpaging_sync_page;

	context->invlpg = nonpaging_invlpg;

	context->update_pte = nonpaging_update_pte;
@@ -3443,8 +3409,7 @@ void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot) 
				continue;



			if (is_large_pte(pt[i])) {

				drop_spte(kvm, &pt[i],

					  shadow_trap_nonpresent_pte);

				drop_spte(kvm, &pt[i]);

				--kvm->stat.lpages;

				continue;

			}

arch/x86/kvm/mmu_audit.c

+0 −12
Original line number Diff line number Diff line
@@ -99,18 +99,6 @@ static void audit_mappings(struct kvm_vcpu *vcpu, u64 *sptep, int level) 
				     "level = %d\n", sp, level);

			return;

		}



		if (*sptep == shadow_notrap_nonpresent_pte) {

			audit_printk(vcpu->kvm, "notrap spte in unsync "

				     "sp: %p\n", sp);

			return;

		}

	}



	if (sp->role.direct && *sptep == shadow_notrap_nonpresent_pte) {

		audit_printk(vcpu->kvm, "notrap spte in direct sp: %p\n",

			     sp);

		return;

	}



	if (!is_shadow_present_pte(*sptep) || !is_last_spte(*sptep, level))

arch/x86/kvm/paging_tmpl.h

+7 −44
Original line number Diff line number Diff line
@@ -337,16 +337,11 @@ static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu, 
				    struct kvm_mmu_page *sp, u64 *spte,

				    pt_element_t gpte)

{

	u64 nonpresent = shadow_trap_nonpresent_pte;



	if (is_rsvd_bits_set(&vcpu->arch.mmu, gpte, PT_PAGE_TABLE_LEVEL))

		goto no_present;



	if (!is_present_gpte(gpte)) {

		if (!sp->unsync)

			nonpresent = shadow_notrap_nonpresent_pte;

	if (!is_present_gpte(gpte))

		goto no_present;

	}



	if (!(gpte & PT_ACCESSED_MASK))

		goto no_present;
@@ -354,7 +349,7 @@ static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu, 
	return false;



no_present:

	drop_spte(vcpu->kvm, spte, nonpresent);

	drop_spte(vcpu->kvm, spte);

	return true;

}
@@ -437,7 +432,7 @@ static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw, 
		if (spte == sptep)

			continue;



		if (*spte != shadow_trap_nonpresent_pte)

		if (is_shadow_present_pte(*spte))

			continue;



		gpte = gptep[i];
@@ -687,11 +682,10 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva) 
			if (is_shadow_present_pte(*sptep)) {

				if (is_large_pte(*sptep))

					--vcpu->kvm->stat.lpages;

				drop_spte(vcpu->kvm, sptep,

					  shadow_trap_nonpresent_pte);

				drop_spte(vcpu->kvm, sptep);

				need_flush = 1;

			} else

				__set_spte(sptep, shadow_trap_nonpresent_pte);

			}



			break;

		}
@@ -751,36 +745,6 @@ static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu *vcpu, gva_t vaddr, 
	return gpa;

}



static void FNAME(prefetch_page)(struct kvm_vcpu *vcpu,

				 struct kvm_mmu_page *sp)

{

	int i, j, offset, r;

	pt_element_t pt[256 / sizeof(pt_element_t)];

	gpa_t pte_gpa;



	if (sp->role.direct

	    || (PTTYPE == 32 && sp->role.level > PT_PAGE_TABLE_LEVEL)) {

		nonpaging_prefetch_page(vcpu, sp);

		return;

	}



	pte_gpa = gfn_to_gpa(sp->gfn);

	if (PTTYPE == 32) {

		offset = sp->role.quadrant << PT64_LEVEL_BITS;

		pte_gpa += offset * sizeof(pt_element_t);

	}



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

		r = kvm_read_guest_atomic(vcpu->kvm, pte_gpa, pt, sizeof pt);

		pte_gpa += ARRAY_SIZE(pt) * sizeof(pt_element_t);

		for (j = 0; j < ARRAY_SIZE(pt); ++j)

			if (r || is_present_gpte(pt[j]))

				sp->spt[i+j] = shadow_trap_nonpresent_pte;

			else

				sp->spt[i+j] = shadow_notrap_nonpresent_pte;

	}

}



/*

 * Using the cached information from sp->gfns is safe because:

 * - The spte has a reference to the struct page, so the pfn for a given gfn
@@ -833,8 +797,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) 
		}



		if (gfn != sp->gfns[i]) {

			drop_spte(vcpu->kvm, &sp->spt[i],

				      shadow_trap_nonpresent_pte);

			drop_spte(vcpu->kvm, &sp->spt[i]);

			vcpu->kvm->tlbs_dirty++;

			continue;

		}