Re: [Xen-devel] [ANNOUNCE] Xen port to Cortex-A15 / ARMv7 with virt extensions

[Catalin Marinas <catalin.marinas@xxxxxxx>]

On Fri, Dec 16, 2011 at 05:38:52PM +0000, David Vrabel wrote:
> On 16/12/11 16:54, Catalin Marinas wrote:
> > On Fri, Dec 16, 2011 at 03:43:57PM +0000, David Vrabel wrote:
> >> On 30/11/11 14:11, Catalin Marinas wrote:
> >>> On 30 November 2011 11:39, Stefano Stabellini
> >>> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> >>>> A git branch is available here (not ready for submission):
> >>>>
> >>>> git://xenbits.xen.org/people/sstabellini/linux-pvhvm.git arm
> >>>>
> >>>> the branch above is based on git://linux-arm.org/linux-2.6.git arm-lpae,
> >>>> even though guests don't really need lpae support to run on Xen.
> >>>
> >>> Indeed, you don't really need LPAE. What you may need though is
> >>> generic timers support for A15, it would allow less Hypervisor traps.
> >>> For up-to-date architecture patches (well, development tree, not
> >>> guaranteed to be stable), I would recommend this (they get into
> >>> mainline at some point):
> >>>
> >>> http://git.kernel.org/?p=linux/kernel/git/cmarinas/linux-arm-arch.git;a=summary
> >>>
> >>> Either use master or just cherry-pick the branches that you are 
> >>> interested in.
> >>
> >> Which branches are required for the Versatile Express with the
> >> Cortex-A15? I merged linux-arm-arch/arm-arch/vexpress in
> > 
> > That's the branch if you only need VE and A15 support
> > 
> >> but I get a
> >> instruction fault immediately after branching to __mmap_switched.
> >>
> >> Is it not setting up the MMU correctly?
> > 
> > Do you run this on a software model? What config options do you use? You
> > would need to enable VEXPRESS_EXTENDED_MEMORY_MAP and
> > ARCH_VEXPRESS_CA15X4.
> 
> The envelope model, yes.  Both those options are enabled.  I've also
> attached the complete config and the model configuration.
> 
> I took a closer look at the diffs between what Stefano had in his tree
> (which included a bunch of LPAE support which I don't have enabled) and
> the kernel boots the addition of some isb's when the MMU is switched on.
> 
> These were added by: "ARM: LPAE: add ISBs around MMU enabling code"
> (commit 1c553c2 in your tree) which is think is only present in the LPAE
> branch.  Is this patch not actually specific to LPAE?  Are there other
> similar patches?

This patch is not specific to LPAE, it's an architecture requirement and
it became visible with A15. The complete patch is here:

http://git.kernel.org/?p=linux/kernel/git/cmarinas/linux-arm-arch.git;a=commitdiff;h=1c553c2afdd7a57cf874a38925bc58381b28150b

though I only kept it in my LPAE branch (which is on it's way to
mainline for 3.3-rc1).

-- 
Catalin

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