Re: [Xen-devel] [PATCH 1/3] xen/vt-d: need barriers to workaround CLFLUSH

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

Chen, Tiejun wrote on 2015-05-04:
> clflush is a light weight but not serializing instruction, so hence
> memory fence is necessary to make sure all load/store visible before flush 
> cache line.
> 
> Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>

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

> ---
>  xen/drivers/passthrough/vtd/x86/vtd.c | 2 ++
>  1 file changed, 2 insertions(+)
> diff --git a/xen/drivers/passthrough/vtd/x86/vtd.c
> b/xen/drivers/passthrough/vtd/x86/vtd.c index 109234e..fd2ff04 100644
> --- a/xen/drivers/passthrough/vtd/x86/vtd.c +++
> b/xen/drivers/passthrough/vtd/x86/vtd.c @@ -56,7 +56,9 @@ unsigned int
> get_cache_line_size(void)
> 
>  void cacheline_flush(char * addr)
>  {
> +    mb();
>      clflush(addr);
> +    mb();
>  }
>  
>  void flush_all_cache()


Best regards,
Yang



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