KVM: x86 emulator: simplify read_emulated

No need split mmio read region into 8-bits pieces since we do it in
emulator_read_write_onepage

Changelog:
  Add a WARN_ON to check read-cache overflow

Acked-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 85b611e13e848608f9bacf311d232664ea1af4c9..2c5d1e65d9d108d1b0bf39a63d877326e5ce3140 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1166,24 +1166,21 @@ static int read_emulated(struct x86_emulate_ctxt *ctxt,
        int rc;
        struct read_cache *mc = &ctxt->mem_read;
 
-       while (size) {
-               int n = min(size, 8u);
-               size -= n;
-               if (mc->pos < mc->end)
-                       goto read_cached;
-
-               rc = ctxt->ops->read_emulated(ctxt, addr, mc->data + mc->end, n,
-                                             &ctxt->exception);
-               if (rc != X86EMUL_CONTINUE)
-                       return rc;
-               mc->end += n;
+       if (mc->pos < mc->end)
+               goto read_cached;
 
-       read_cached:
-               memcpy(dest, mc->data + mc->pos, n);
-               mc->pos += n;
-               dest += n;
-               addr += n;
-       }
+       WARN_ON((mc->end + size) >= sizeof(mc->data));
+
+       rc = ctxt->ops->read_emulated(ctxt, addr, mc->data + mc->end, size,
+                                     &ctxt->exception);
+       if (rc != X86EMUL_CONTINUE)
+               return rc;
+
+       mc->end += size;
+
+read_cached:
+       memcpy(dest, mc->data + mc->pos, size);
+       mc->pos += size;
        return X86EMUL_CONTINUE;
 }