[Libvir] PATCH: support Xen 3.0.5

Richard W.M. Jones rjones at redhat.com
Thu Apr 12 09:02:45 UTC 2007

  A Man Without A Country Daniel P. Berrange wrote:
> I've been doing some testing with current xen-unstable (ie what will very
> shortly be 3.0.5) and came across a whole bunch of things which needed
> fixing - some expected, others not expected. The attached patch addresses
> the following issues:

As a general question about policy, are we going to support every rev of 
the HV interface?  If Xen change the interface again before 3.0.5 will 
we support this "pre-3.0.5" and the final interface?

>   - Many of the hypercalls have their structs changed so that int64_t
>     or 'foo *' members are always 64-bit aligned even on 32-bit platforms.
>     This is part of the work to allow 32-bit Dom0/DomU to work on 64-bit
>     hypervisor. 
>     For the int64_t types I had to annotate with __attribute__((aligned(8))).
>     This did not work for pointer data types, so I for those I had to do
>     a more complex hack with
>         union {
>            foo *v;
>            int64_t pad __attribute__((aligned(8)))
>         }

What is the problem here?  I did some tests and it seems to work just fine:

/* Test alignment of pointers.
  * Richard Jones <rjones~at~redhat~dot~com>

#include <stdio.h>

#undef offsetof
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)

struct s {
   char c;
   //int v;
   //int v __attribute__((aligned(16)));
   int *v __attribute__((aligned(16)));
   //struct s *v __attribute__((aligned(16)));

main ()
   printf ("offset = %d\n", offsetof (struct s, v));
   return 0;

$ gcc -Wall -Werror align.c -o align
$ ./align
offset = 16
$ arch
$ gcc --version
gcc (GCC) 3.3.5 (Debian 1:3.3.5-13)
Copyright (C) 2003 Free Software Foundation, Inc. [etc]

>   - The unified Xen driver broke the GetVCPUs method - it was mistakenly
>     checking for return value == 0, instead of > 0. Trivial fix.


> I've tested all this on a 32-bit Dom0 running on 32-bit HV, and 64-bit HV,
> but not tested a 64-bit Dom0 on 64-bit HV. I'm pretty sure it'll work,but
> if anyone is runnning 64-on-64 please test this patch.

I don't have 3.0.5 to test here, but I can possibly test this on Monday. 
  In the meantime I eyeballed the patch and from what I can tell it 
seems fine.


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