Re: [PATCH 5/6 v5] kvm: booke: clear host tlb reference flag on guest tlb invalidation

[Scott Wood <scottwood@freescale.com>]

On Fri, 2013-09-20 at 13:04 -0500, Bhushan Bharat-R65777 wrote:
> 
> > -----Original Message-----
> > From: Wood Scott-B07421
> > Sent: Friday, September 20, 2013 9:48 PM
> > To: Bhushan Bharat-R65777
> > Cc: Wood Scott-B07421; benh@kernel.crashing.org; agraf@suse.de;
> > paulus@samba.org; kvm@vger.kernel.org; kvm-ppc@vger.kernel.org; linuxppc-
> > dev@lists.ozlabs.org
> > Subject: Re: [PATCH 5/6 v5] kvm: booke: clear host tlb reference flag on guest
> > tlb invalidation
> > 
> > On Thu, 2013-09-19 at 23:19 -0500, Bhushan Bharat-R65777 wrote:
> > > We uses these bit flags only for TLB1 and if size of stlbe is 4K then
> > > we set E500_TLB_TLB0  otherwise we set E500_TLB_BITMAP. Although I
> > > think that E500_TLB_BITMAP should be set only if stlbe size is less
> > > than gtlbe size.
> > 
> > Why?  Even if there's only one bit set in the map, we need it to keep track of
> > which entry was used.
> 
> If there is one entry then will not this be simple/faster to not lookup bitmap and guest->host array?
> A flag indicate it is 1:1 map and this is physical address.

The difference would be negligible, and you'd have added overhead (both
runtime and complexity) of making this a special case.

-Scott