[PATCH] KVM: MMU: Fold fetch_guest() into init_walker()

It is never necessary to fetch a guest entry from an intermediate page table
level (except for large pages), so avoid some confusion by always descending
into the lowest possible level.

Rename init_walker() to walk_addr() as it is no longer restricted to
initialization.

Signed-off-by: Avi Kivity <avi@qumranet.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 47 insertions, 58 deletions

diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
index 3a35c8067dec..963d80e2271f 100644
--- a/drivers/kvm/paging_tmpl.h
+++ b/drivers/kvm/paging_tmpl.h
@@ -54,14 +54,19 @@ struct guest_walker {
         int level;
         gfn_t table_gfn;
         pt_element_t *table;
+        pt_element_t *ptep;
         pt_element_t inherited_ar;
 };
 
-static void FNAME(init_walker)(struct guest_walker *walker,
-                               struct kvm_vcpu *vcpu)
+/*
+ * Fetch a guest pte for a guest virtual address
+ */
+static void FNAME(walk_addr)(struct guest_walker *walker,
+                             struct kvm_vcpu *vcpu, gva_t addr)
 {
         hpa_t hpa;
         struct kvm_memory_slot *slot;
+        pt_element_t *ptep;
 
         walker->level = vcpu->mmu.root_level;
         walker->table_gfn = (vcpu->cr3 & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
@@ -75,6 +80,38 @@ static void FNAME(init_walker)(struct guest_walker *walker,
         walker->table = (pt_element_t *)( (unsigned long)walker->table |
                 (unsigned long)(vcpu->cr3 & ~(PAGE_MASK | CR3_FLAGS_MASK)) );
         walker->inherited_ar = PT_USER_MASK | PT_WRITABLE_MASK;
+
+        for (;;) {
+                int index = PT_INDEX(addr, walker->level);
+                hpa_t paddr;
+
+                ptep = &walker->table[index];
+                ASSERT(((unsigned long)walker->table & PAGE_MASK) ==
+                       ((unsigned long)ptep & PAGE_MASK));
+
+                /* Don't set accessed bit on PAE PDPTRs */
+                if (vcpu->mmu.root_level != 3 || walker->level != 3)
+                        if ((*ptep & (PT_PRESENT_MASK | PT_ACCESSED_MASK))
+                            == PT_PRESENT_MASK)
+                                *ptep |= PT_ACCESSED_MASK;
+
+                if (!is_present_pte(*ptep) ||
+                    walker->level == PT_PAGE_TABLE_LEVEL ||
+                    (walker->level == PT_DIRECTORY_LEVEL &&
+                     (*ptep & PT_PAGE_SIZE_MASK) &&
+                     (PTTYPE == 64 || is_pse(vcpu))))
+                        break;
+
+                if (walker->level != 3 || is_long_mode(vcpu))
+                        walker->inherited_ar &= walker->table[index];
+                walker->table_gfn = (*ptep & PT_BASE_ADDR_MASK) >> PAGE_SHIFT;
+                paddr = safe_gpa_to_hpa(vcpu, *ptep & PT_BASE_ADDR_MASK);
+                kunmap_atomic(walker->table, KM_USER0);
+                walker->table = kmap_atomic(pfn_to_page(paddr >> PAGE_SHIFT),
+                                            KM_USER0);
+                --walker->level;
+        }
+        walker->ptep = ptep;
 }
 
 static void FNAME(release_walker)(struct guest_walker *walker)
@@ -110,41 +147,6 @@ static void FNAME(set_pde)(struct kvm_vcpu *vcpu, u64 guest_pde,
 }
 
 /*
- * Fetch a guest pte from a specific level in the paging hierarchy.
- */
-static pt_element_t *FNAME(fetch_guest)(struct kvm_vcpu *vcpu,
-                                        struct guest_walker *walker,
-                                        int level,
-                                        gva_t addr)
-{
-
-        ASSERT(level > 0  && level <= walker->level);
-
-        for (;;) {
-                int index = PT_INDEX(addr, walker->level);
-                hpa_t paddr;
-
-                ASSERT(((unsigned long)walker->table & PAGE_MASK) ==
-                       ((unsigned long)&walker->table[index] & PAGE_MASK));
-                if (level == walker->level ||
-                    !is_present_pte(walker->table[index]) ||
-                    (walker->level == PT_DIRECTORY_LEVEL &&
-                     (walker->table[index] & PT_PAGE_SIZE_MASK) &&
-                     (PTTYPE == 64 || is_pse(vcpu))))
-                        return &walker->table[index];
-                if (walker->level != 3 || is_long_mode(vcpu))
-                        walker->inherited_ar &= walker->table[index];
-                walker->table_gfn = (walker->table[index] & PT_BASE_ADDR_MASK)
-                        >> PAGE_SHIFT;
-                paddr = safe_gpa_to_hpa(vcpu, walker->table[index] & PT_BASE_ADDR_MASK);
-                kunmap_atomic(walker->table, KM_USER0);
-                walker->table = kmap_atomic(pfn_to_page(paddr >> PAGE_SHIFT),
-                                            KM_USER0);
-                --walker->level;
-        }
-}
-
-/*
  * Fetch a shadow pte for a specific level in the paging hierarchy.
  */
 static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
@@ -153,6 +155,10 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
         hpa_t shadow_addr;
         int level;
         u64 *prev_shadow_ent = NULL;
+        pt_element_t *guest_ent = walker->ptep;
+
+        if (!is_present_pte(*guest_ent))
+                return NULL;
 
         shadow_addr = vcpu->mmu.root_hpa;
         level = vcpu->mmu.shadow_root_level;
@@ -160,7 +166,6 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
         for (; ; level--) {
                 u32 index = SHADOW_PT_INDEX(addr, level);
                 u64 *shadow_ent = ((u64 *)__va(shadow_addr)) + index;
-                pt_element_t *guest_ent;
                 u64 shadow_pte;
 
                 if (is_present_pte(*shadow_ent) || is_io_pte(*shadow_ent)) {
@@ -171,21 +176,6 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
                         continue;
                 }
 
-                if (PTTYPE == 32 && level > PT32_ROOT_LEVEL) {
-                        ASSERT(level == PT32E_ROOT_LEVEL);
-                        guest_ent = FNAME(fetch_guest)(vcpu, walker,
-                                                       PT32_ROOT_LEVEL, addr);
-                } else
-                        guest_ent = FNAME(fetch_guest)(vcpu, walker,
-                                                       level, addr);
-
-                if (!is_present_pte(*guest_ent))
-                        return NULL;
-
-                /* Don't set accessed bit on PAE PDPTRs */
-                if (vcpu->mmu.root_level != 3 || walker->level != 3)
-                        *guest_ent |= PT_ACCESSED_MASK;
-
                 if (level == PT_PAGE_TABLE_LEVEL) {
 
                         if (walker->level == PT_DIRECTORY_LEVEL) {
@@ -253,7 +243,7 @@ static int FNAME(fix_write_pf)(struct kvm_vcpu *vcpu,
                         *shadow_ent &= ~PT_USER_MASK;
                 }
 
-        guest_ent = FNAME(fetch_guest)(vcpu, walker, PT_PAGE_TABLE_LEVEL, addr);
+        guest_ent = walker->ptep;
 
         if (!is_present_pte(*guest_ent)) {
                 *shadow_ent = 0;
@@ -296,7 +286,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
          * Look up the shadow pte for the faulting address.
          */
         for (;;) {
-                FNAME(init_walker)(&walker, vcpu);
+                FNAME(walk_addr)(&walker, vcpu, addr);
                 shadow_pte = FNAME(fetch)(vcpu, addr, &walker);
                 if (IS_ERR(shadow_pte)) {  /* must be -ENOMEM */
                         nonpaging_flush(vcpu);
@@ -357,9 +347,8 @@ static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr)
         pt_element_t guest_pte;
         gpa_t gpa;
 
-        FNAME(init_walker)(&walker, vcpu);
-        guest_pte = *FNAME(fetch_guest)(vcpu, &walker, PT_PAGE_TABLE_LEVEL,
-                                        vaddr);
+        FNAME(walk_addr)(&walker, vcpu, vaddr);
+        guest_pte = *walker.ptep;
         FNAME(release_walker)(&walker);
 
         if (!is_present_pte(guest_pte))