Re: [PATCH 1/2] x86/shadow: defer/avoid paging_mfn_is_dirty() invocation

[Tim Deegan <tim@xxxxxxx>]

At 11:35 +0100 on 01 Dec (1638358515), Jan Beulich wrote:
> paging_mfn_is_dirty() is moderately expensive, so avoid its use unless
> its result might actually change anything. This means moving the
> surrounding if() down below all other checks that can result in clearing
> _PAGE_RW from sflags, in order to then check whether _PAGE_RW is
> actually still set there before calling the function.
> 
> While moving the block of code, fold two if()s and make a few style
> adjustments.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Tim Deegan <tim@xxxxxxx>

> ---
> TBD: Perhaps the dirty-VRAM piece also wants moving down a little, such
>      that all three "level == 1" conditionals can be folded?

I have no strong feelings on that either way.

Cheers,

Tim.