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: 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).

Thanks
Kevin

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