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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Thu, 30 Jun 2016 21:08:53 +1000
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Subject: Re: [Qemu-devel] [PATCH 2/2] ppc: Fix 64K pages support in full
 emulation
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To: Anton Blanchard <anton@samba.org>, =?ISO-8859-1?Q?C=E9dric?= Le Goater <clg@kaod.org>
Cc: David Gibson <david@gibson.dropbear.id.au>, qemu-ppc@nongnu.org, qemu-devel@nongnu.org

On Thu, 2016-06-30 at 20:56 +1000, Anton Blanchard wrote:
> Hi,
> 
> > From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> > 
> > We were always advertising only 4K & 16M. Additionally the code wasn't
> > properly matching the page size with the PTE content, which meant we
> > could potentially hit an incorrect PTE if the guest used multiple
> > sizes.
> > 
> > Finally, honor the CPU capabilities when decoding the size from the
> > SLB so we don't try to use 64K pages on 970.
> > 
> > This still doesn't add support for MPSS (Multiple Page Sizes per
> > Segment)
> 
> This is causing issues booting an Ubuntu yakety cloud image. I'm
> running on a ppc64le box (I don't think it reproduces on x86-64).

I don't completely understand your repro instructions ... I'm surprised
there would be a difference here between ppc64le and x86_64 hosts... they
are both 64-bit LE hosts and the MMU stuff is host code, not JITed (well
there is JITed code for the qemu TLB lookups but that's always 4k).

Very strange ... I need to reproduce and see what the heck is doing.

Cheers,
Ben.

> #cloud-config
> password: password
> chpasswd: { expire: False }
> ssh_pwauth: True
> EOF
> 
> cloud-localds my-seed.img my-user-data
> 
> wget -N https://cloud-images.ubuntu.com/yakkety/current/yakkety-server-cloudimg-ppc64el.img
> 
> qemu-system-ppc64 -M pseries -cpu POWER8 -nographic -vga none -m 4G -drive file=test.img -drive file=my-seed.img -net user -net nic
> 
> The cloud-init scripts never finish, so the ubuntu user's
> password is never updated. With the above cloud config you
> should be able to log in with ubuntu/password.
> 
> Anton