Re: [Xen-devel] [PATCH 1/4] VT-d/qinval: make local variable used for communication with IOMMU "volatile"

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

Jan Beulich wrote on 2014-06-16:
> 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@xxxxxxxx>

Acked-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>

> 
> --- 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;
>


Best regards,
Yang



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