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Date: Wed, 15 Jan 2020 08:16:56 -0600
From: Patrick Williams <patrick@stwcx.xyz>
To: Jeremy Kerr <jk@ozlabs.org>
Cc: "Khetan, Sharad" <sharad.khetan@intel.com>,
 Deepak Kodihalli <dkodihal@linux.vnet.ibm.com>,
 Andrew Jeffery <andrew@aj.id.au>, Vijay Khemka <vijaykhemka@fb.com>,
 rgrs <rgrs@protonmail.com>,
 "openbmc@lists.ozlabs.org" <openbmc@lists.ozlabs.org>,
 "Bhat, Sumanth" <sumanth.bhat@intel.com>,
 "Winiarska, Iwona" <iwona.winiarska@intel.com>
Subject: Re: MCTP over PCI on AST2500
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On Wed, Jan 15, 2020 at 09:51:38PM +0800, Jeremy Kerr wrote:
> Hi Patrick,
>=20
> > > Just a suggestion - you probably don't want to be passing MCTP
> > > messages over dbus - this is something we learnt from the IPMI
> > > implementation.
> >=20
> > Is there a pointer to this "lesson learned" or the issues surrounding
> > it?  It seems like the btbridge is still using dbus, so I assume
> > host-ipmid is as well.
> >=20
> > https://github.com/openbmc/btbridge/blob/master/btbridged.c#L47
> >=20
> > I'm curious to understand what the issues were/are.
>=20
> No, nothing that anyone had specifically documented. I recall there
> were concerns with shuffling larger amounts of data over dbus,
> particularly for things like firmware update over IPMI. Because we're
> using a dbus signal for incoming messages, we could potentially be
> writing a lot of data to multiple processes - and more than necessary
> if those processes haven't set up their dbus matches correctly.
>=20
> I don't think there's enough concern to change existing code over for,
> more just a consideration for future designs, of which this is one.
>=20

Maybe by that time bus1 will be a mature replacement for dbus. ;)

Thanks for the reply.

--=20
Patrick Williams

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