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

On Fri, 2013-09-20 at 13:04 -0500, Bhushan Bharat-R65777 wrote:

quoted

-----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:

quoted

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