KVM: x86 emulator: prefetch up to 15 bytes of the instruction executed

Instead of fetching one byte at a time, prefetch 15 bytes (or until the next
page boundary) to avoid guest page table walks.

Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/kvm/x86_emulate.h b/drivers/kvm/x86_emulate.h
index a62bf14bbf89..4603b2bf3488 100644
--- a/drivers/kvm/x86_emulate.h
+++ b/drivers/kvm/x86_emulate.h
@@ -108,6 +108,12 @@ struct operand {
         unsigned long val, orig_val, *ptr;
 };
 
+struct fetch_cache {
+        u8 data[15];
+        unsigned long start;
+        unsigned long end;
+};
+
 struct decode_cache {
         u8 twobyte;
         u8 b;
@@ -130,6 +136,7 @@ struct decode_cache {
         u8 use_modrm_ea;
         unsigned long modrm_ea;
         unsigned long modrm_val;
+        struct fetch_cache fetch;
 };
 
 struct x86_emulate_ctxt {