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Date: Thu, 19 Jun 2014 07:30:27 +0200
From: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
Message-ID: <20140619053027.GA14925@toto>
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Subject: Re: [Qemu-devel] [PATCH v3 07/32] target-arm: add non-secure
 Translation Block flag
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To: Sergey Fedorov <serge.fdrv@gmail.com>
Cc: peter.maydell@linaro.org, peter.crosthwaite@xilinx.com, Fabian Aggeler <aggelerf@ethz.ch>, qemu-devel@nongnu.org, greg.bellows@linaro.org, christoffer.dall@linaro.org

On Tue, Jun 17, 2014 at 02:07:11PM +0400, Sergey Fedorov wrote:
> On 17.06.2014 13:15, Edgar E. Iglesias wrote:
> > Hi, I think the patch looks OK but I'm unsure if it brings any benefits
> > unless we add separate TLBs for S and NS.
> >
> > I noticed that TTBR0 gets banked in the series, but are changes to
> > SCR.NS flushing the TLBs? I might have missed that from the patches.
> > You'll need it unless we add separate S/NS TLBs.
> >
> > Considering that changes to SCR.NS will flush the TLBs, the
> > use of a per TB ns flag is limited, unless I am missing something...
> 
> Hi Edgar,
> 
> This seems to be used in patch 19/32.

Yes, I actually meant limited use as in having the NS flag in translation
time brings limited performance win or none.

But looking more carefuly, the way we handle cp regs requires the ns bit
at translation time to support direct loads of cpregs (without calling
out to tcg helpers). That is probably enough to motivate the tb flag.

Cheers,
Edgar

> 
> // Sergey
> 
> >
> > Cheers,
> > Edgar
>