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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: Fri, 02 Sep 2016 22:13:44 +1000
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Subject: Re: [Qemu-devel] [PATCH RFC 0/4] Enable MTTCG on PowerPC
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To: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>, qemu-ppc@nongnu.org, alex.bennee@linaro.org, david@gibson.dropbear.id.au, rth@twiddle.net
Cc: qemu-devel@nongnu.org

On Fri, 2016-09-02 at 13:09 +0530, Nikunj A Dadhania wrote:
> Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
>=20
> >=20
> > On Fri, 2016-09-02 at 12:02 +0530, Nikunj A Dadhania wrote:
> > >=20
> > > The series is a first attempt at enabling Multi-Threaded TCG on
> > > PowerPC.
> > > Changes that were needed to enable PowerPC are pretty simple;
> > >=20
> > > Patch 01: Take a iothread lock during hcall, as hcall can
> > > generate io requests
> > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A002: For TCG, we were harcoding =
smt as 1, this gets rid of
> > > the limitation
> >=20
> > If we do this, we need to implement the shared SPRs properly
>=20
> Sure, will have a look at it.

My idea was to have a bitmap of SPRs that are shared. When hitting a
shared one, after a write, we call a helper that "sync" the update to
all the other threads using run_on_cpu.

> >=20
> > and the inter-thread doorbells...
>=20
> You mean the below ?
>=20
> >=20
> > >=20
> > > TODO
> > > =3D=3D=3D=3D
> > > Implement msgsndp instructions(door-bell), newer kernels enable
> > > it=C2=A0
> > > depending on the PVR. I have been using following workaround to
> > > boot.
> > > https://github.com/nikunjad/qemu/commit/2c10052c5f93418a6b920e6ba
> > > 3ce1813fcf50bc4
>=20
> Regards,
> Nikunj