Re: [Xen-devel] [PATCHv6 2/2] x86/ept: defer the invalidation until the p2m lock is released

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: David Vrabel [mailto:david.vrabel@xxxxxxxxxx]
> Sent: Monday, February 01, 2016 10:50 PM
> 
> On 20/12/15 06:56, Tian, Kevin wrote:
> >> From: David Vrabel [mailto:david.vrabel@xxxxxxxxxx]
> >> Sent: Friday, December 18, 2015 9:51 PM
> >>
> >> Holding the p2m lock while calling ept_sync_domain() is very expensive
> >> since it does a on_selected_cpus() call.  IPIs on many socket machines
> >> can be very slows and on_selected_cpus() is serialized.
> >>
> >> It is safe to defer the invalidate until the p2m lock is released
> >> except for two cases:
> >>
> >> 1. When freeing a page table page (since partial translations may be
> >>    cached).
> >> 2. When reclaiming a zero page as part of PoD.
> >>
> >> For these cases, add p2m_tlb_flush_sync() calls which will immediately
> >> perform the invalidate before the page is freed or reclaimed.
> >>
> >> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> >
> > In a quick glimpse the patch is OK. Will find a time to think about it more
> > carefully since this part is tricky (also allow others to comment before
> > my ack in EPT part).
> 
> Ping?  Did you get more time to think about this patch?
> 

Sorry for delay on this. I saw you've sent out a v7 on this. Queued to
be reviewed tomorrow.

Thanks
Kevin

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