[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/kvm.h b/drivers/kvm/kvm.h
index abe40dd..58b9deb 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -89,14 +89,53 @@
typedef u64 hpa_t;
typedef unsigned long hfn_t;
+#define NR_PTE_CHAIN_ENTRIES 5
+
+struct kvm_pte_chain {
+ u64 *parent_ptes[NR_PTE_CHAIN_ENTRIES];
+ struct hlist_node link;
+};
+
+/*
+ * kvm_mmu_page_role, below, is defined as:
+ *
+ * bits 0:3 - total guest paging levels (2-4, or zero for real mode)
+ * bits 4:7 - page table level for this shadow (1-4)
+ * bits 8:9 - page table quadrant for 2-level guests
+ * bit 16 - "metaphysical" - gfn is not a real page (huge page/real mode)
+ */
+union kvm_mmu_page_role {
+ unsigned word;
+ struct {
+ unsigned glevels : 4;
+ unsigned level : 4;
+ unsigned quadrant : 2;
+ unsigned pad_for_nice_hex_output : 6;
+ unsigned metaphysical : 1;
+ };
+};
+
struct kvm_mmu_page {
struct list_head link;
+ struct hlist_node hash_link;
+
+ /*
+ * The following two entries are used to key the shadow page in the
+ * hash table.
+ */
+ gfn_t gfn;
+ union kvm_mmu_page_role role;
+
hpa_t page_hpa;
unsigned long slot_bitmap; /* One bit set per slot which has memory
* in this shadow page.
*/
int global; /* Set if all ptes in this page are global */
- u64 *parent_pte;
+ int multimapped; /* More than one parent_pte? */
+ union {
+ u64 *parent_pte; /* !multimapped */
+ struct hlist_head parent_ptes; /* multimapped, kvm_pte_chain */
+ };
};
struct vmcs {
@@ -235,7 +274,11 @@
spinlock_t lock; /* protects everything except vcpus */
int nmemslots;
struct kvm_memory_slot memslots[KVM_MEMORY_SLOTS];
+ /*
+ * Hash table of struct kvm_mmu_page.
+ */
struct list_head active_mmu_pages;
+ struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];
struct kvm_vcpu vcpus[KVM_MAX_VCPUS];
int memory_config_version;
int busy;