Re: [Xen-devel] [PATCH v2] xen: arm: correctly configure NSACR.

[Ian Campbell <ijc@xxxxxxxxxxxxxx>]

On Mon, 2013-07-15 at 14:00 +0100, Julien Grall wrote:
> On 07/15/2013 12:22 PM, Stefano Stabellini wrote:
> > On Mon, 15 Jul 2013, Ian Campbell wrote:
> >> From: Ian Campbell <ian.campbell@xxxxxxxxxx>
> >>
> >> Previously we were setting it up twice, the second time neglecting to set 
> >> the
> >> NS_SMP bit.
> >>
> >> NSACR.NS_SMP is a processor specific bit which on Cortex-A7 and -A15 
> >> regulates
> >> access to the (also processor specific) ACTLR.SMP bit. Not setting 
> >> NSACR.NS_SMP
> >> meant that Xen's attempts to set ACTLR.SMP was silently ignored. Setting 
> >> this
> >> bit is required in order to cause the processor to take part in cache and 
> >> TLB
> >> coherency protocols. Failure to set this bit leads to random memory 
> >> corruption
> >> in guests (although nothing like as catestrophic as you might expect!).
>                                           ^
>                                        catastrophic

I knew being a spelling pendant would eventually come back and bite
me ;-)

> >>
> >> An alternative fix would have been to set ACTLR.SMP when in Secure World,
> >> however Linux expects to set ACTLR.SMP itself in NS mode, so it's a good 
> >> bet
> >> that bootloaders will set NSACR.NS_SMP instead.
> >>
> >> While here switch to a read-modify-write of NSACR to preserve any existing 
> >> bits
> >> -- seems safer.
> >>
> >> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> >> ---
> >> v2: Modify rather than overwrite NSACR.
> > 
> > Acked-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> 
> Except the minor typo:
> Acked-by: Julien Grall <julien.grall@xxxxxxxxxx>

Typo fixed + applied, thanks.



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