All of lore.kernel.org
 help / color / mirror / Atom feed
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Anthony Liguori <anthony@codemonkey.ws>
Cc: "Liu Ping Fan" <pingfank@linux.vnet.ibm.com>,
	"Jan Kiszka" <jan.kiszka@web.de>,
	"qemu-devel Developers" <qemu-devel@nongnu.org>,
	"Alexander Graf" <agraf@suse.de>,
	"qemu-ppc@nongnu.org list:PowerPC" <qemu-ppc@nongnu.org>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Hervé Poussineau" <hpoussin@reactos.org>,
	"Andreas Färber" <afaerber@suse.de>
Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH v3 11/14] ioport: Switch dispatching to memory core layer
Date: Sat, 13 Jul 2013 08:59:57 +1000	[thread overview]
Message-ID: <1373669997.19894.210.camel@pasglop> (raw)
In-Reply-To: <87vc4f1tts.fsf@codemonkey.ws>

On Fri, 2013-07-12 at 14:06 -0500, Anthony Liguori wrote:
> > In the light of this, I think there should only be one endianness
> for 
> > all memory accesses (which could be changed at runtime),
> 
> We already do this, it's "host native endian".

The simple fact that you used the word "endian" makes it broken here :-)

If the guest has done a byte reverse access for example, what you have
is not "host native endian" anymore.

The simple fact that you use "endian" to describe what you carry around
is a source of wrongness and errors. It's misleading and people always
get that wrong (I did a bloody talk on the matter at two conferences now
and it seems people really don't get what endianness really is about).

> > and all 
> > bridges/devices should ask for "same endianness as parent" or
> "reverse 
> > endianness as parent", but not for big, little, or native
> endianness.
> 
> I/O doesn't propagate so there's no way to say something like this.
> That's the fundamental problem IMHO.

There is no such thing as "endianness of parent" again. This is all
wrong. Wrong terminology, wrong concepts.

Do not try to use the "endian" attribute on a bus or bridge, it will
only confuse things further.

Stick to what is the byte order of your transport (much more precise
term, ie. which byte is the lowest address within the host variable that
carries the access).

Ben.

  reply	other threads:[~2013-07-12 23:00 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-06-22  6:06 [Qemu-devel] [PATCH v3 00/14] Refactor portio dispatching Jan Kiszka
2013-06-22  6:06 ` [Qemu-devel] [PATCH v3 01/14] adlib: replace register_ioport* Jan Kiszka
2013-06-22  6:06 ` [Qemu-devel] [PATCH v3 02/14] applesmc: " Jan Kiszka
2013-06-22  6:06 ` [Qemu-devel] [PATCH v3 03/14] wdt_ib700: " Jan Kiszka
2013-06-22  6:06 ` [Qemu-devel] [PATCH v3 04/14] i82374: " Jan Kiszka
2013-06-22  6:06 ` [Qemu-devel] [PATCH v3 05/14] prep: " Jan Kiszka
2013-06-22  6:06 ` [Qemu-devel] [PATCH v3 06/14] vt82c686: " Jan Kiszka
2013-06-22  6:07 ` [Qemu-devel] [PATCH v3 07/14] Privatize register_ioport_read/write Jan Kiszka
2013-06-22  6:07 ` [Qemu-devel] [PATCH v3 08/14] isa: implement isa_is_ioport_assigned via memory_region_find Jan Kiszka
2013-06-22  6:07 ` [Qemu-devel] [PATCH v3 09/14] vmware-vga: Accept unaligned I/O accesses Jan Kiszka
2013-06-22  6:07 ` [Qemu-devel] [PATCH v3 10/14] xen: Mark fixed platform I/O as unaligned Jan Kiszka
2013-06-22  6:07 ` [Qemu-devel] [PATCH v3 11/14] ioport: Switch dispatching to memory core layer Jan Kiszka
2013-06-23 20:50   ` Hervé Poussineau
2013-06-24  6:07     ` Jan Kiszka
2013-07-11 12:29       ` Alexander Graf
2013-07-11 12:34         ` Alexander Graf
2013-07-11 12:46           ` Andreas Färber
2013-07-11 12:48             ` Alexander Graf
2013-07-11 13:28               ` Alexander Graf
2013-07-11 13:35                 ` Alexander Graf
2013-07-11 22:30                 ` [Qemu-devel] [Qemu-ppc] " Benjamin Herrenschmidt
2013-07-11 22:32                 ` Benjamin Herrenschmidt
2013-07-12  3:18                   ` Alexander Graf
2013-07-12 11:35                     ` Benjamin Herrenschmidt
2013-07-12 17:04                       ` Hervé Poussineau
2013-07-12 19:06                         ` Anthony Liguori
2013-07-12 22:59                           ` Benjamin Herrenschmidt [this message]
2013-07-12 22:39                         ` Benjamin Herrenschmidt
2013-07-12 17:49                       ` Anthony Liguori
2013-07-12 18:26                         ` Peter Maydell
2013-07-12 22:50                           ` Benjamin Herrenschmidt
2013-07-12 23:10                             ` Peter Maydell
2013-07-12 23:49                               ` Benjamin Herrenschmidt
2013-07-15 14:01                               ` Anthony Liguori
2013-07-15 14:10                                 ` Peter Maydell
2013-07-15 14:16                                 ` Benjamin Herrenschmidt
2013-07-12 22:44                         ` Benjamin Herrenschmidt
2013-07-13 14:38             ` [Qemu-devel] " Paolo Bonzini
2013-07-13 15:22               ` Anthony Liguori
2013-07-13 18:11                 ` Hervé Poussineau
2013-07-14  6:15                 ` Paolo Bonzini
2013-07-14 13:05                   ` Anthony Liguori
2013-07-14 14:58                     ` Peter Maydell
2013-07-14 15:18                       ` Anthony Liguori
2013-07-14 16:50                         ` Peter Maydell
2013-07-16  7:18                         ` Jan Kiszka
2013-07-16  7:33                           ` Paolo Bonzini
2013-07-16 16:59                             ` Hervé Poussineau
2013-07-16 17:12                               ` Paolo Bonzini
2013-07-12 12:56           ` Anthony Liguori
2013-07-12 14:30             ` Alexander Graf
2013-07-19 11:09         ` [Qemu-devel] BUG: " Alexey Kardashevskiy
2013-07-19 12:49           ` Paolo Bonzini
2013-07-19 15:48             ` Alexey Kardashevskiy
2013-07-20  0:55               ` Alexey Kardashevskiy
2013-07-20  1:11                 ` Alexey Kardashevskiy
2013-07-20 10:11                   ` Paolo Bonzini
2013-07-20 20:53                     ` Edgar E. Iglesias
2013-07-21 15:13                     ` Hervé Poussineau
2013-07-22 10:25                       ` Paolo Bonzini
2013-06-24  8:45     ` [Qemu-devel] [PATCH v4 " Jan Kiszka
2013-07-12 19:36     ` [Qemu-devel] [PATCH v3 " Anthony Liguori
2013-06-22  6:07 ` [Qemu-devel] [PATCH v3 12/14] ioport: Remove unused old dispatching services Jan Kiszka
2013-06-22  6:07 ` [Qemu-devel] [PATCH v3 13/14] vmport: Disentangle read handler type from portio Jan Kiszka
2013-06-22  6:07 ` [Qemu-devel] [PATCH v3 14/14] ioport: Move portio types to ioport.h Jan Kiszka
2013-06-23 20:45 ` [Qemu-devel] [PATCH v3 00/14] Refactor portio dispatching Hervé Poussineau

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1373669997.19894.210.camel@pasglop \
    --to=benh@kernel.crashing.org \
    --cc=afaerber@suse.de \
    --cc=agraf@suse.de \
    --cc=anthony@codemonkey.ws \
    --cc=hpoussin@reactos.org \
    --cc=jan.kiszka@web.de \
    --cc=pbonzini@redhat.com \
    --cc=pingfank@linux.vnet.ibm.com \
    --cc=qemu-devel@nongnu.org \
    --cc=qemu-ppc@nongnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.