Re: [Xen-devel] [RFC 21/22] xen/arm: p2m: Re-implement p2m_set_mem_access using p2m_{set, get}_entry

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 07/28/2016 05:51 PM, Julien Grall wrote:
> The function p2m_set_mem_access can be re-implemented using the generic
> functions p2m_get_entry and __p2m_set_entry.
> 
> Note that because of the implementation of p2m_get_entry, a TLB
> invalidation instruction will be issued for each 4KB page. Therefore the
> performance of memaccess will be impacted, however the function is now
> safe on all the processors.
> 
> Also the function apply_p2m_changes is dropped completely as it is not
> unused anymore.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> Cc: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
> Cc: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
> 
> ---
>     I have not ran any performance test with memaccess for now, but I
>     expect an important and unavoidable impact because of how memaccess
>     has been designed to workaround hardware limitation. Note that might
>     be possible to re-work memaccess work on superpage but this should
>     be done in a separate patch.
> ---
>  xen/arch/arm/p2m.c | 329 
> +++++++----------------------------------------------
>  1 file changed, 38 insertions(+), 291 deletions(-)

Thanks for the CC!

This seems to only impact ARM, are there any planned changes for x86
along these lines as well?


Thanks,
Razvan

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