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From: Pawel Moll <pawel.moll@arm.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"virtualization@lists.linux-foundation.org"
	<virtualization@lists.linux-foundation.org>
Subject: Re: [PATCH] virtio-spec: Define virtio-mmio registers as LE
Date: Wed, 06 Mar 2013 15:10:15 +0000	[thread overview]
Message-ID: <1362582615.3105.45.camel@hornet> (raw)
In-Reply-To: <87fw0ad7sr.fsf@rustcorp.com.au>

On Tue, 2013-03-05 at 00:11 +0000, Rusty Russell wrote:
> Pawel Moll <pawel.moll@arm.com> writes:
> > On Fri, 2013-03-01 at 11:21 +0000, Marc Zyngier wrote:
> >> > Having said that, Rusty was contemplating enforcing LE config space in
> >> > the new PCI layout...
> >> 
> >> I wouldn't complain about that, and would like to see a similar thing on
> >> MMIO.
> >
> > Wherever PCI goes, MMIO follows :-)
> 
> Yes, but if you switch from 'guest-endian' to 'little-endian' how will
> you tell?  For PCI, we'd detect it by using the new layout.

The version register/value. At some point of time there will be a
new(ish) MMIO layout anyway to deal with 64-bit addresses, replacing the
ring page number with two 32-bit hi/lo physical address registers. This
was discussed not long after the driver got merged...

> I'd rather you specify MMIO as little endian, and we fix the kernel
> config accessors to be endian aware (ie. 8, 16, 32, 64-bit accessors).
> Since noone BE is using MMIO right now, it's safe...

That's absolutely fine with me, however I don't see anything I could do
in the virtio_mmio driver and spec - the virtio_config_ops specifies
get/set as void * operations and I simply do byte-by-byte copy. Have I
missed some config/endianess/PCI related discussion?

Paweł


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WARNING: multiple messages have this Message-ID (diff)
From: Pawel Moll <pawel.moll@arm.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Marc Zyngier <Marc.Zyngier@arm.com>,
	"virtualization@lists.linux-foundation.org" 
	<virtualization@lists.linux-foundation.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [PATCH] virtio-spec: Define virtio-mmio registers as LE
Date: Wed, 06 Mar 2013 15:10:15 +0000	[thread overview]
Message-ID: <1362582615.3105.45.camel@hornet> (raw)
In-Reply-To: <87fw0ad7sr.fsf@rustcorp.com.au>

On Tue, 2013-03-05 at 00:11 +0000, Rusty Russell wrote:
> Pawel Moll <pawel.moll@arm.com> writes:
> > On Fri, 2013-03-01 at 11:21 +0000, Marc Zyngier wrote:
> >> > Having said that, Rusty was contemplating enforcing LE config space in
> >> > the new PCI layout...
> >> 
> >> I wouldn't complain about that, and would like to see a similar thing on
> >> MMIO.
> >
> > Wherever PCI goes, MMIO follows :-)
> 
> Yes, but if you switch from 'guest-endian' to 'little-endian' how will
> you tell?  For PCI, we'd detect it by using the new layout.

The version register/value. At some point of time there will be a
new(ish) MMIO layout anyway to deal with 64-bit addresses, replacing the
ring page number with two 32-bit hi/lo physical address registers. This
was discussed not long after the driver got merged...

> I'd rather you specify MMIO as little endian, and we fix the kernel
> config accessors to be endian aware (ie. 8, 16, 32, 64-bit accessors).
> Since noone BE is using MMIO right now, it's safe...

That's absolutely fine with me, however I don't see anything I could do
in the virtio_mmio driver and spec - the virtio_config_ops specifies
get/set as void * operations and I simply do byte-by-byte copy. Have I
missed some config/endianess/PCI related discussion?

Paweł



  reply	other threads:[~2013-03-06 15:10 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-02-13 14:25 [RFC PATCH] virt_mmio: fix signature checking for BE guests Marc Zyngier
2013-02-13 14:25 ` Marc Zyngier
2013-02-13 15:08 ` Pawel Moll
2013-02-13 15:08   ` Pawel Moll
2013-02-13 15:28   ` Marc Zyngier
2013-02-13 15:28     ` Marc Zyngier
2013-02-13 15:46     ` Pawel Moll
2013-02-13 15:46       ` Pawel Moll
2013-02-13 16:40       ` Marc Zyngier
2013-02-13 16:40         ` Marc Zyngier
2013-02-13 16:53     ` Michael S. Tsirkin
2013-02-13 16:53       ` Michael S. Tsirkin
2013-02-13 17:04       ` Marc Zyngier
2013-02-13 17:04         ` Marc Zyngier
2013-02-14  0:22       ` Rusty Russell
2013-02-14  0:22         ` Rusty Russell
2013-02-14 10:54         ` [PATCH] virtio-spec: Define virtio-mmio registers as LE Pawel Moll
2013-02-14 10:54           ` Pawel Moll
2013-02-15  3:57           ` Rusty Russell
2013-02-15  3:57             ` Rusty Russell
2013-03-01 10:41           ` Marc Zyngier
2013-03-01 10:41             ` Marc Zyngier
2013-03-01 10:50             ` Pawel Moll
2013-03-01 10:50               ` Pawel Moll
2013-03-01 11:21               ` Marc Zyngier
2013-03-01 11:21                 ` Marc Zyngier
2013-03-01 12:37                 ` Pawel Moll
2013-03-01 12:37                   ` Pawel Moll
2013-03-01 13:16                   ` Marc Zyngier
2013-03-01 13:16                     ` Marc Zyngier
2013-03-05  0:11                   ` Rusty Russell
2013-03-05  0:11                     ` Rusty Russell
2013-03-06 15:10                     ` Pawel Moll [this message]
2013-03-06 15:10                       ` Pawel Moll
2013-03-07  6:36                       ` Rusty Russell
2013-03-07  6:36                         ` Rusty Russell
2013-02-15  0:07     ` [RFC PATCH] virt_mmio: fix signature checking for BE guests Benjamin Herrenschmidt
2013-02-15  0:07     ` Benjamin Herrenschmidt

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