Re: [PATCH RFC 12/15] Factor out generic architecture code

[Thomas Huth <thuth@redhat.com>]

On 11.04.2016 13:04, Alexander Gordeev wrote:
> This rework is a prerequisite for the forthcoming pci-testdev
> implementation. Basically, only generic port IO accessors are
> needed, but it turned out touching io/smp/mm files is needed.
> This update should likely be more comprehensive and split into
> several commits.
> 
> Cc: Thomas Huth <thuth@redhat.com>
> Cc: Andrew Jones <drjones@redhat.com>
> Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
> ---
>  lib/asm-generic/io.h | 55 ++++++++++++++++++++++++++++++++++++++++++++++++----
>  lib/x86/asm/page.h   |  1 +
>  lib/x86/io.h         | 36 ++++++++++++++++++++++------------
>  lib/x86/smp.h        |  4 ----
>  lib/x86/vm.c         |  1 -
>  lib/x86/vm.h         | 12 +-----------
>  x86/eventinj.c       |  7 +------
>  x86/kvmclock.c       |  1 +
>  8 files changed, 79 insertions(+), 38 deletions(-)
>  create mode 100644 lib/x86/asm/page.h
> 
> diff --git a/lib/asm-generic/io.h b/lib/asm-generic/io.h
> index 49283d6eb020..bd78f3586b9e 100644
> --- a/lib/asm-generic/io.h
> +++ b/lib/asm-generic/io.h
> @@ -127,6 +127,9 @@ static inline u64 __bswap64(u64 x)
>  	({ u64 __r = !__cpu_is_be() ? __bswap64(x) : ((u64)x); __r; })
>  #define cpu_to_be64 be64_to_cpu
>  
> +#ifndef mb
> +#define mb() do { } while (0)
> +#endif

I think it would be better to at least use a
 asm volatile ("":::"memory")
here to make sure that the compiler does not try to optimize memory
access before and behind the barrier?

 Thomas