[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH 3/6] Fix last page errors in page_set_flags and

From: Richard Henderson
Subject: Re: [Qemu-devel] [PATCH 3/6] Fix last page errors in page_set_flags and page_check_range.
Date: Fri, 12 Feb 2010 12:16:37 -0800
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100120 Fedora/3.0.1-1.fc12 Thunderbird/3.0.1

On 02/12/2010 11:47 AM, Blue Swirl wrote:
Please make separate patches for unrelated changes. Now the essence of
the patch is very hard to see. Also pure formatting changes are not
very useful.

Is this just about page_get_flags, or was there some other pure formatting change to which you object? For instance:

-    if (start + len < start)
-        /* we've wrapped around */
+    if (start + len - 1 < start) {
+        /* We've wrapped around.  */
        return -1;
+    }

Only the first line is required to fix an off-by-one error. But if I don't add the braces, generally the patch will be bounced for that.

-        /* We may be called for host regions that are outside guest
-           address space.  */

Why remove the comment, is it no longer true?

Yes, after the entire patch series is applied. Indeed, I believe that many of the addresses rejected here were *not* in fact outside the guest address space, merely that page_find_alloc did not accurately know what the guest address space was.

I think it was a mistake to ever consider usage of this function with out-of-band addresses as valid -- it adds a great deal of confusion.

I could add an assertion here to make sure, if you like.

If this were C++, it might have been interesting to try to use the type system to keep the host and guest address spaces forcibly separate. But since this is plain C, I think wrapping everything in structures and access macros would just be too ugly.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]