[PATCH] KVM: MMU: Shadow page table caching
Define a hashtable for caching shadow page tables. Look up the cache on
context switch (cr3 change) or during page faults.
The key to the cache is a combination of
- the guest page table frame number
- the number of paging levels in the guest
* we can cache real mode, 32-bit mode, pae, and long mode page
tables simultaneously. this is useful for smp bootup.
- the guest page table table
* some kernels use a page as both a page table and a page directory. this
allows multiple shadow pages to exist for that page, one per level
- the "quadrant"
* 32-bit mode page tables span 4MB, whereas a shadow page table spans
2MB. similarly, a 32-bit page directory spans 4GB, while a shadow
page directory spans 1GB. the quadrant allows caching up to 4 shadow page
tables for one guest page in one level.
- a "metaphysical" bit
* for real mode, and for pse pages, there is no guest page table, so set
the bit to avoid write protecting the page.
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>
diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index da4d7dd..47c699c 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -26,8 +26,8 @@
#include "vmx.h"
#include "kvm.h"
-#define pgprintk(x...) do { } while (0)
-#define rmap_printk(x...) do { } while (0)
+#define pgprintk(x...) do { printk(x); } while (0)
+#define rmap_printk(x...) do { printk(x); } while (0)
#define ASSERT(x) \
if (!(x)) { \
@@ -35,8 +35,10 @@
__FILE__, __LINE__, #x); \
}
-#define PT64_ENT_PER_PAGE 512
-#define PT32_ENT_PER_PAGE 1024
+#define PT64_PT_BITS 9
+#define PT64_ENT_PER_PAGE (1 << PT64_PT_BITS)
+#define PT32_PT_BITS 10
+#define PT32_ENT_PER_PAGE (1 << PT32_PT_BITS)
#define PT_WRITABLE_SHIFT 1
@@ -292,6 +294,11 @@
return 1;
}
+static unsigned kvm_page_table_hashfn(gfn_t gfn)
+{
+ return gfn;
+}
+
static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu,
u64 *parent_pte)
{
@@ -306,10 +313,147 @@
ASSERT(is_empty_shadow_page(page->page_hpa));
page->slot_bitmap = 0;
page->global = 1;
+ page->multimapped = 0;
page->parent_pte = parent_pte;
return page;
}
+static void mmu_page_add_parent_pte(struct kvm_mmu_page *page, u64 *parent_pte)
+{
+ struct kvm_pte_chain *pte_chain;
+ struct hlist_node *node;
+ int i;
+
+ if (!parent_pte)
+ return;
+ if (!page->multimapped) {
+ u64 *old = page->parent_pte;
+
+ if (!old) {
+ page->parent_pte = parent_pte;
+ return;
+ }
+ page->multimapped = 1;
+ pte_chain = kzalloc(sizeof(struct kvm_pte_chain), GFP_NOWAIT);
+ BUG_ON(!pte_chain);
+ INIT_HLIST_HEAD(&page->parent_ptes);
+ hlist_add_head(&pte_chain->link, &page->parent_ptes);
+ pte_chain->parent_ptes[0] = old;
+ }
+ hlist_for_each_entry(pte_chain, node, &page->parent_ptes, link) {
+ if (pte_chain->parent_ptes[NR_PTE_CHAIN_ENTRIES-1])
+ continue;
+ for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i)
+ if (!pte_chain->parent_ptes[i]) {
+ pte_chain->parent_ptes[i] = parent_pte;
+ return;
+ }
+ }
+ pte_chain = kzalloc(sizeof(struct kvm_pte_chain), GFP_NOWAIT);
+ BUG_ON(!pte_chain);
+ hlist_add_head(&pte_chain->link, &page->parent_ptes);
+ pte_chain->parent_ptes[0] = parent_pte;
+}
+
+static void mmu_page_remove_parent_pte(struct kvm_mmu_page *page,
+ u64 *parent_pte)
+{
+ struct kvm_pte_chain *pte_chain;
+ struct hlist_node *node;
+ int i;
+
+ if (!page->multimapped) {
+ BUG_ON(page->parent_pte != parent_pte);
+ page->parent_pte = NULL;
+ return;
+ }
+ hlist_for_each_entry(pte_chain, node, &page->parent_ptes, link)
+ for (i = 0; i < NR_PTE_CHAIN_ENTRIES; ++i) {
+ if (!pte_chain->parent_ptes[i])
+ break;
+ if (pte_chain->parent_ptes[i] != parent_pte)
+ continue;
+ while (i + 1 < NR_PTE_CHAIN_ENTRIES) {
+ pte_chain->parent_ptes[i]
+ = pte_chain->parent_ptes[i + 1];
+ ++i;
+ }
+ pte_chain->parent_ptes[i] = NULL;
+ return;
+ }
+ BUG();
+}
+
+static struct kvm_mmu_page *kvm_mmu_lookup_page(struct kvm_vcpu *vcpu,
+ gfn_t gfn)
+{
+ unsigned index;
+ struct hlist_head *bucket;
+ struct kvm_mmu_page *page;
+ struct hlist_node *node;
+
+ pgprintk("%s: looking for gfn %lx\n", __FUNCTION__, gfn);
+ index = kvm_page_table_hashfn(gfn) % KVM_NUM_MMU_PAGES;
+ bucket = &vcpu->kvm->mmu_page_hash[index];
+ hlist_for_each_entry(page, node, bucket, hash_link)
+ if (page->gfn == gfn && !page->role.metaphysical) {
+ pgprintk("%s: found role %x\n",
+ __FUNCTION__, page->role.word);
+ return page;
+ }
+ return NULL;
+}
+
+static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
+ gfn_t gfn,
+ gva_t gaddr,
+ unsigned level,
+ int metaphysical,
+ u64 *parent_pte)
+{
+ union kvm_mmu_page_role role;
+ unsigned index;
+ unsigned quadrant;
+ struct hlist_head *bucket;
+ struct kvm_mmu_page *page;
+ struct hlist_node *node;
+
+ role.word = 0;
+ role.glevels = vcpu->mmu.root_level;
+ role.level = level;
+ role.metaphysical = metaphysical;
+ if (vcpu->mmu.root_level <= PT32_ROOT_LEVEL) {
+ quadrant = gaddr >> (PAGE_SHIFT + (PT64_PT_BITS * level));
+ quadrant &= (1 << ((PT32_PT_BITS - PT64_PT_BITS) * level)) - 1;
+ role.quadrant = quadrant;
+ }
+ pgprintk("%s: looking gfn %lx role %x\n", __FUNCTION__,
+ gfn, role.word);
+ index = kvm_page_table_hashfn(gfn) % KVM_NUM_MMU_PAGES;
+ bucket = &vcpu->kvm->mmu_page_hash[index];
+ hlist_for_each_entry(page, node, bucket, hash_link)
+ if (page->gfn == gfn && page->role.word == role.word) {
+ mmu_page_add_parent_pte(page, parent_pte);
+ pgprintk("%s: found\n", __FUNCTION__);
+ return page;
+ }
+ page = kvm_mmu_alloc_page(vcpu, parent_pte);
+ if (!page)
+ return page;
+ pgprintk("%s: adding gfn %lx role %x\n", __FUNCTION__, gfn, role.word);
+ page->gfn = gfn;
+ page->role = role;
+ hlist_add_head(&page->hash_link, bucket);
+ return page;
+}
+
+static void kvm_mmu_put_page(struct kvm_vcpu *vcpu,
+ struct kvm_mmu_page *page,
+ u64 *parent_pte)
+{
+ mmu_page_remove_parent_pte(page, parent_pte);
+}
+
static void page_header_update_slot(struct kvm *kvm, void *pte, gpa_t gpa)
{
int slot = memslot_id(kvm, gfn_to_memslot(kvm, gpa >> PAGE_SHIFT));
@@ -389,11 +533,15 @@
for (; ; level--) {
u32 index = PT64_INDEX(v, level);
u64 *table;
+ u64 pte;
ASSERT(VALID_PAGE(table_addr));
table = __va(table_addr);
if (level == 1) {
+ pte = table[index];
+ if (is_present_pte(pte) && is_writeble_pte(pte))
+ return 0;
mark_page_dirty(vcpu->kvm, v >> PAGE_SHIFT);
page_header_update_slot(vcpu->kvm, table, v);
table[index] = p | PT_PRESENT_MASK | PT_WRITABLE_MASK |
@@ -404,8 +552,13 @@
if (table[index] == 0) {
struct kvm_mmu_page *new_table;
+ gfn_t pseudo_gfn;
- new_table = kvm_mmu_alloc_page(vcpu, &table[index]);
+ pseudo_gfn = (v & PT64_DIR_BASE_ADDR_MASK)
+ >> PAGE_SHIFT;
+ new_table = kvm_mmu_get_page(vcpu, pseudo_gfn,
+ v, level - 1,
+ 1, &table[index]);
if (!new_table) {
pgprintk("nonpaging_map: ENOMEM\n");
return -ENOMEM;
@@ -427,7 +580,6 @@
hpa_t root = vcpu->mmu.root_hpa;
ASSERT(VALID_PAGE(root));
- release_pt_page_64(vcpu, root, PT64_ROOT_LEVEL);
vcpu->mmu.root_hpa = INVALID_PAGE;
return;
}
@@ -437,7 +589,6 @@
ASSERT(VALID_PAGE(root));
root &= PT64_BASE_ADDR_MASK;
- release_pt_page_64(vcpu, root, PT32E_ROOT_LEVEL - 1);
vcpu->mmu.pae_root[i] = INVALID_PAGE;
}
vcpu->mmu.root_hpa = INVALID_PAGE;
@@ -446,13 +597,16 @@
static void mmu_alloc_roots(struct kvm_vcpu *vcpu)
{
int i;
+ gfn_t root_gfn;
+ root_gfn = vcpu->cr3 >> PAGE_SHIFT;
#ifdef CONFIG_X86_64
if (vcpu->mmu.shadow_root_level == PT64_ROOT_LEVEL) {
hpa_t root = vcpu->mmu.root_hpa;
ASSERT(!VALID_PAGE(root));
- root = kvm_mmu_alloc_page(vcpu, NULL)->page_hpa;
+ root = kvm_mmu_get_page(vcpu, root_gfn, 0,
+ PT64_ROOT_LEVEL, 0, NULL)->page_hpa;
vcpu->mmu.root_hpa = root;
return;
}
@@ -461,7 +615,13 @@
hpa_t root = vcpu->mmu.pae_root[i];
ASSERT(!VALID_PAGE(root));
- root = kvm_mmu_alloc_page(vcpu, NULL)->page_hpa;
+ if (vcpu->mmu.root_level == PT32E_ROOT_LEVEL)
+ root_gfn = vcpu->pdptrs[i] >> PAGE_SHIFT;
+ else if (vcpu->mmu.root_level == 0)
+ root_gfn = 0;
+ root = kvm_mmu_get_page(vcpu, root_gfn, i << 30,
+ PT32_ROOT_LEVEL, !is_paging(vcpu),
+ NULL)->page_hpa;
vcpu->mmu.pae_root[i] = root | PT_PRESENT_MASK;
}
vcpu->mmu.root_hpa = __pa(vcpu->mmu.pae_root);
@@ -529,7 +689,7 @@
context->inval_page = nonpaging_inval_page;
context->gva_to_gpa = nonpaging_gva_to_gpa;
context->free = nonpaging_free;
- context->root_level = PT32E_ROOT_LEVEL;
+ context->root_level = 0;
context->shadow_root_level = PT32E_ROOT_LEVEL;
mmu_alloc_roots(vcpu);
ASSERT(VALID_PAGE(context->root_hpa));
@@ -537,29 +697,18 @@
return 0;
}
-
static void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu)
{
- struct kvm_mmu_page *page, *npage;
-
- list_for_each_entry_safe(page, npage, &vcpu->kvm->active_mmu_pages,
- link) {
- if (page->global)
- continue;
-
- if (!page->parent_pte)
- continue;
-
- *page->parent_pte = 0;
- release_pt_page_64(vcpu, page->page_hpa, 1);
- }
++kvm_stat.tlb_flush;
kvm_arch_ops->tlb_flush(vcpu);
}
static void paging_new_cr3(struct kvm_vcpu *vcpu)
{
+ mmu_free_roots(vcpu);
+ mmu_alloc_roots(vcpu);
kvm_mmu_flush_tlb(vcpu);
+ kvm_arch_ops->set_cr3(vcpu, vcpu->mmu.root_hpa);
}
static void mark_pagetable_nonglobal(void *shadow_pte)
@@ -578,6 +727,16 @@
*shadow_pte |= access_bits << PT_SHADOW_BITS_OFFSET;
if (!dirty)
access_bits &= ~PT_WRITABLE_MASK;
+ if (access_bits & PT_WRITABLE_MASK) {
+ struct kvm_mmu_page *shadow;
+
+ shadow = kvm_mmu_lookup_page(vcpu, gaddr >> PAGE_SHIFT);
+ if (shadow)
+ pgprintk("%s: found shadow page for %lx, marking ro\n",
+ __FUNCTION__, (gfn_t)(gaddr >> PAGE_SHIFT));
+ if (shadow)
+ access_bits &= ~PT_WRITABLE_MASK;
+ }
if (access_bits & PT_WRITABLE_MASK)
mark_page_dirty(vcpu->kvm, gaddr >> PAGE_SHIFT);