Re: [PATCH v6 2/2] xen: move TLB-flush filtering out into populate_physmap during vm creation

[Dario Faggioli <dario.faggioli@citrix.com>]

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On Tue, 2016-09-20 at 12:20 +0100, George Dunlap wrote:
> On 20/09/16 03:31, Dongli Zhang wrote:
> > 
> > This patch implemented parts of TODO left in commit id
> > a902c12ee45fc9389eb8fe54eeddaf267a555c58 (More efficient TLB-flush
> > filtering in alloc_heap_pages()). It moved TLB-flush filtering out
> > into
> > populate_physmap. Because of TLB-flush in alloc_heap_pages, it's
> > very slow
> > to create a guest with memory size of more than 100GB on host with
> > 100+
> > cpus.
> > 
> > This patch introduced a "MEMF_no_tlbflush" bit to memflags to
> > indicate
> > whether TLB-flush should be done in alloc_heap_pages or its caller
> > populate_physmap.  Once this bit is set in memflags,
> > alloc_heap_pages will
> > ignore TLB-flush. To use this bit after vm is created might lead to
> > security issue, that is, this would make pages accessible to the
> > guest B,
> > when guest A may still have a cached mapping to them.
> > 
> > Therefore, this patch also introduced a "creation_finished" field
> > to struct
> > domain to indicate whether this domain has ever got unpaused by
> > hypervisor.
> > MEMF_no_tlbflush can be set only during vm creation phase when
> > creation_finished is still false before this domain gets unpaused
> > for the
> > first time.
> > 
> > Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
> 
> Acked-by: George Dunlap <george.dunlap@citrix.com>
> 
FWIW, and if I'm still in time:

Reviewed-by: Dario Faggioli <dario.faggioli@citrix.com>

Regards,
Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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