Re: [PATCH 0/4] memory: Add memory_region_msync() & make NVMe emulated device generic

[Beata Michalska]

On Fri, 8 May 2020 at 07:33, Paolo Bonzini <address@hidden> wrote:
>
> On 08/05/20 08:24, Philippe Mathieu-Daudé wrote:
> > It is not clear if dccvap_writefn() really needs
> > memory_region_writeback() or could use memory_region_msync().
>
> Indeed, I don't understand the code and why it matters that
> mr->dirty_log_mask is nonzero.
>
> mr->dirty_log_mask tells if dirty tracking has been enabled, not if the
> page is dirty.  It would always be true during live migration and when
> running on TCG, but otherwise it would always be false.
>
> Beata, can you explain what you had in mind? :)
>
It has been a while ... , but the intention there was to skip the sync
if there is nothing to be synced in the first place - so for performance
reasons. I honestly do not recall why I went for the dirty_log_mask,
as that seems not  to be the right choice .

BR
Beata
> Paolo
>