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Date: Mon, 4 Apr 2016 20:43:46 +1000
From: Anton Blanchard <anton@samba.org>
Message-ID: <20160404204346.1cf44df8@kryten>
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Subject: Re: [Qemu-devel] PR KVM and TM issues
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To: Alexey Kardashevskiy <aik@ozlabs.ru>, Michael Ellerman <mpe@ellerman.id.au>, Paul Mackerras <paulus@samba.org>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Michael Neuling <mikey@neuling.org>, David Gibson <david@gibson.dropbear.id.au>, Alexander Graf <agraf@suse.de>
Cc: qemu-ppc@nongnu.org, linuxppc-dev@lists.ozlabs.org, qemu-devel@nongnu.org

Hi Alexey,

> > I can't get an Ubuntu Wily guest to boot on an Ubuntu Wily host in
> > PR KVM mode. The kernel in both cases is 4.2. To reproduce:
> >
> > wget -N https://cloud-images.ubuntu.com/wily/current/wily-server-cloudimg-ppc64el-disk1.img
> >
> > qemu-system-ppc64 -cpu POWER8 -enable-kvm -machine pseries,kvm-type=PR -m 4G -nographic -vga none -drive file=wily-server-cloudimg-ppc64el-disk1.img,if=virtio
> >
> > Should TM work inside a PR KVM guest?
> 
> If I read the kernel code correctly (kvmppc_set_one_reg_hv vs. 
> kvmppc_set_one_reg_pr), no, it should not be expected to work.

I see a couple of issues, patches to follow:

1. QEMU needs to clear the TM feature bit in the ibm,pa-features array
when running in PR KVM mode.

2. Linux needs to clear the user TM feature bits if TM gets disabled
at runtime via the ibm,pa-features bit.

Anton