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Re: [Qemu-devel] [Qemu-ppc] Determining interest in PPC e500spin, yield,


From: David Gibson
Subject: Re: [Qemu-devel] [Qemu-ppc] Determining interest in PPC e500spin, yield, and openpic patches
Date: Thu, 16 Jun 2016 16:37:02 +1000
User-agent: Mutt/1.6.1 (2016-04-27)

On Wed, Jun 15, 2016 at 01:12:37PM -0700, address@hidden wrote:
> David Gibson <address@hidden> wrote on 06/14/2016 11:17:57 
> PM:
> Aaron Larson <address@hidden>
> 
> AL> 1. There is a defect in ppce500_spin.c:spin_kick() that creates an
> AL>    incorrectly sized TLB entry.  This was reported as bug
> AL>    https://bugs.launchpad.net/qemu/+bug/1587535  I can provide a
> AL>    patch if desired.
> 
> DG> Absolutely.
> 
> OK, I'll start with this one.   Let me know if there is anything you'd 
> like me to do
> with that bug report.
> 
> When e500 PPC is booted multi-core, the non-boot cores are started via
> the spin table.  ppce500_spin.c:spin_kick() calls
> mmubooke_create_initial_mapping() to allocate a 64MB TLB entry, but
> the created TLB entry is only 256KB.
> 
> The root cause is that the function computing the size of the TLB
> entry, namely booke206_page_size_to_tlb assumes MAS1.TSIZE as defined
> by latter PPC cores, specifically n to the power of FOUR * 1KB. The
> result is then used by mmubooke_create_initial_mapping using
> MAS1_TSIZE_SHIFT, but MAS1_TSIZE_SHIFT is defined assuming TLB entries
> are n to the power of TWO * 1KB. I.e., a difference of shift=7 or
> shift=8.
> 
> Simply changing MAS1_TSIZE_SHIFT from 7 to 8 is not appropriate since
> the macro is used elsewhere.
> 
> The following patch has a fix for that, and also raises a separate
> issue that I'd be happy to resolve after getting some guidance.

Ok, thanks for sending this, but there are some procedural things
you'll need to check before we can go ahead.  We generally prefer
patches to be sent inline, rather than as attachments (it makes adding
review comments much easier), and you'll need to apply a Signed-off-by
line before I could merge it.  There are more details on the
procedures for submitting patches at:
        http://wiki.qemu.org/Contribute/SubmitAPatch

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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