Re: [Xen-devel] [PATCH v2 3/5] dbg_rw_guest_mem: Conditionally enable debug log output

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-01-07 at 19:25 -0500, Don Slutz wrote:
> If dbg_debug is non-zero, output debug.
> 
> Include put_gfn debug logging.
> 
> Here is a smaple output at dbg_debug == 2:
> 
> (XEN) [2014-01-07 03:20:09] gmem:addr:8f56 buf:00000000006e2020 len:$1 
> domid:1 toaddr:0 dp:ffff83083e5fe000
> (XEN) [2014-01-07 03:20:09] vaddr:8f56 domid:1
> (XEN) [2014-01-07 03:20:09] X: vaddr:8f56 domid:1 mfn:64331a
> (XEN) [2014-01-07 03:20:09] R: addr:8f56 pagecnt=1 domid:1 gfn:8
> (XEN) [2014-01-07 03:20:09] gmem:exit:len:$0
> (XEN) [2014-01-07 03:20:09] gmem:addr:8f57 buf:00000000006e2020 len:$1 
> domid:1 toaddr:0 dp:ffff83083e5fe000
> (XEN) [2014-01-07 03:20:09] vaddr:8f57 domid:1
> (XEN) [2014-01-07 03:20:09] X: vaddr:8f57 domid:1 mfn:64331a
> (XEN) [2014-01-07 03:20:09] R: addr:8f57 pagecnt=1 domid:1 gfn:8
> (XEN) [2014-01-07 03:20:09] gmem:exit:len:$0
> (XEN) [2014-01-07 03:20:09] gmem:addr:6ae9168b buf:00000000006e2020 len:$2 
> domid:1 toaddr:0 dp:ffff83083e5fe000
> (XEN) [2014-01-07 03:20:09] vaddr:6ae9168b domid:1
> (XEN) [2014-01-07 03:20:09] X: vaddr:6ae9168b domid:1 mfn:ffffffffffffffff
> (XEN) [2014-01-07 03:20:09] R: domid:1 gfn:6ae91
> (XEN) [2014-01-07 03:20:09] gmem:exit:len:$2
> 
> Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>
> ---
>  xen/arch/x86/debug.c | 54 
> +++++++++++++++++++++++++---------------------------
>  1 file changed, 26 insertions(+), 28 deletions(-)
> 
> diff --git a/xen/arch/x86/debug.c b/xen/arch/x86/debug.c
> index ba6a64d..777e5ba 100644
> --- a/xen/arch/x86/debug.c
> +++ b/xen/arch/x86/debug.c
> @@ -30,16 +30,9 @@
>   * gdbsx, etc..
>   */
>  
> -#ifdef XEN_KDB_CONFIG
> -#include "../kdb/include/kdbdefs.h"
> -#include "../kdb/include/kdbproto.h"
> -#define DBGP(...) {(kdbdbg) ? kdbp(__VA_ARGS__):0;}
> -#define DBGP1(...) {(kdbdbg>1) ? kdbp(__VA_ARGS__):0;}
> -#define DBGP2(...) {(kdbdbg>2) ? kdbp(__VA_ARGS__):0;}
> -#else
> -#define DBGP1(...) ((void)0)
> -#define DBGP2(...) ((void)0)
> -#endif
> +static volatile int dbg_debug;

Using volatile is almost always wrong. Why do you think it is needed
here?

If anything this variable is exactly the opposite, i..e __read_mostly or
even const (given that I can't see anything which writes it I suppose
this is a compile time setting?)

Ian.


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