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: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

7 files changed, 33 insertions, 132 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a7225746ed96..1810a6b51bab 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -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)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 8da1400ab581..a198a5b2f04e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -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);
 
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 2f8543c65fa3..5334b4e9ecc7 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -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;
                         }
diff --git a/arch/x86/kvm/mmu_audit.c b/arch/x86/kvm/mmu_audit.c
index 5f6223b8bcf7..2460a265be23 100644
--- a/arch/x86/kvm/mmu_audit.c
+++ b/arch/x86/kvm/mmu_audit.c
@@ -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))
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index fa3b54bbce6b..a4565df501cd 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -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;
                 }
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f5b49c7fc89d..a644acb6ed80 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -49,9 +49,6 @@
 MODULE_AUTHOR("Qumranet");
 MODULE_LICENSE("GPL");
 
-static int __read_mostly bypass_guest_pf = 1;
-module_param(bypass_guest_pf, bool, S_IRUGO);
-
 static int __read_mostly enable_vpid = 1;
 module_param_named(vpid, enable_vpid, bool, 0444);
 
@@ -3632,8 +3629,8 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
                 vmcs_write32(PLE_WINDOW, ple_window);
         }
 
-        vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, !!bypass_guest_pf);
-        vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, !!bypass_guest_pf);
+        vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, 0);
+        vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, 0);
         vmcs_write32(CR3_TARGET_COUNT, 0);           /* 22.2.1 */
 
         vmcs_write16(HOST_FS_SELECTOR, 0);            /* 22.2.4 */
@@ -7103,16 +7100,12 @@ static int __init vmx_init(void)
         vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_EIP, false);
 
         if (enable_ept) {
-                bypass_guest_pf = 0;
                 kvm_mmu_set_mask_ptes(0ull, 0ull, 0ull, 0ull,
                                 VMX_EPT_EXECUTABLE_MASK);
                 kvm_enable_tdp();
         } else
                 kvm_disable_tdp();
 
-        if (bypass_guest_pf)
-                kvm_mmu_set_nonpresent_ptes(~0xffeull, 0ull);
-
         return 0;
 
 out3:
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 028a0f25e8a0..64c42d90112b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5091,7 +5091,6 @@ int kvm_arch_init(void *opaque)
         kvm_init_msr_list();
 
         kvm_x86_ops = ops;
-        kvm_mmu_set_nonpresent_ptes(0ull, 0ull);
         kvm_mmu_set_mask_ptes(PT_USER_MASK, PT_ACCESSED_MASK,
                         PT_DIRTY_MASK, PT64_NX_MASK, 0);