[PATCH 4/33] KVM: MMU: Fold fetch_guest() into init_walker()

Avi Kivity
2007-01-04T15:53:05Z

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-atKUWr5tajBWk0Htik3J/w@public.gmane.org>

Index: linux-2.6/drivers/kvm/paging_tmpl.h
===================================================================
--- linux-2.6.orig/drivers/kvm/paging_tmpl.h
+++ linux-2.6/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 gu
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_vc
}

/*
- * 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
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
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
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 kv
*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_
* 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 kv
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))