2 files changed, 43 insertions, 2 deletions

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 8e2162fc6f70..6e7f774d1751 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -414,8 +414,7 @@ static u16 twobyte_table[256] = {
 /* Fetch next part of the instruction being emulated. */
 #define insn_fetch(_type, _size, _eip)                                  \
 ({      unsigned long _x;                                               \
-        rc = ops->read_std((unsigned long)(_eip) + ctxt->cs_base, &_x,  \
-                           (_size), ctxt->vcpu);                        \
+        rc = do_insn_fetch(ctxt, ops, (_eip), &_x, (_size));            \
         if (rc != 0)                                                    \
                 goto done;                                              \
         (_eip) += (_size);                                              \
@@ -446,6 +445,41 @@ static u16 twobyte_table[256] = {
                 register_address_increment(c->eip, rel);                \
         } while (0)
 
+static int do_fetch_insn_byte(struct x86_emulate_ctxt *ctxt,
+                              struct x86_emulate_ops *ops,
+                              unsigned long linear, u8 *dest)
+{
+        struct fetch_cache *fc = &ctxt->decode.fetch;
+        int rc;
+        int size;
+
+        if (linear < fc->start || linear >= fc->end) {
+                size = min(15UL, PAGE_SIZE - offset_in_page(linear));
+                rc = ops->read_std(linear, fc->data, size, ctxt->vcpu);
+                if (rc)
+                        return rc;
+                fc->start = linear;
+                fc->end = linear + size;
+        }
+        *dest = fc->data[linear - fc->start];
+        return 0;
+}
+
+static int do_insn_fetch(struct x86_emulate_ctxt *ctxt,
+                         struct x86_emulate_ops *ops,
+                         unsigned long eip, void *dest, unsigned size)
+{
+        int rc = 0;
+
+        eip += ctxt->cs_base;
+        while (size--) {
+                rc = do_fetch_insn_byte(ctxt, ops, eip++, dest++);
+                if (rc)
+                        return rc;
+        }
+        return 0;
+}
+
 /*
  * Given the 'reg' portion of a ModRM byte, and a register block, return a
  * pointer into the block that addresses the relevant register.
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 {