On 16/06/14 13:47, Jan Beulich wrote:
> Without that there is - afaict - nothing preventing the compiler from
> putting the variable into a register for the duration of the wait loop.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

I seem to remember Tim saying that behaviour like this is covered by
-fno-strict-aliasing

Either way, it is certainly correct for it to be marked as volatile.

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

>
> --- a/xen/drivers/passthrough/vtd/qinval.c
> +++ b/xen/drivers/passthrough/vtd/qinval.c
> @@ -196,7 +196,7 @@ static int queue_invalidate_wait(struct 
>      u8 iflag, u8 sw, u8 fn)
>  {
>      s_time_t start_time;
> -    u32 poll_slot = QINVAL_STAT_INIT;
> +    volatile u32 poll_slot = QINVAL_STAT_INIT;
>      int index = -1;
>      int ret = -1;
>      unsigned long flags;
>
>
>
>
>
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