From: Paul Brook <paul@codesourcery.com>
To: Blue Swirl <blauwirbel@gmail.com>
Cc: "Andreas Färber" <andreas.faerber@web.de>,
"Alexander Graf" <agraf@suse.de>,
"QEMU-devel Developers" <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH 01/15] exec: introduce endianness swapped mmio
Date: Sat, 27 Nov 2010 10:24:00 +0000 [thread overview]
Message-ID: <201011271024.01876.paul@codesourcery.com> (raw)
In-Reply-To: <AANLkTik6G2ja=d-nG3wixsvza-Jfm6cB5NQwWbT-_RLu@mail.gmail.com>
> > Switching endianness of a CPU generally does not effect the endianness of
> > the CPU/peripheral busses. It makes the CPU byteswap accesses before
> > they are seen by either memory or devices.
> >
> > In theory it might be possible to avoid redundant byteswaps if you're
> > really clever. In practice you still have to handle the fact that your
> > devices are a different endianness to RAM, so it probably doesn't gain
> > you a whole lot.
>
> Sparc64 MMU can also perform byte swapping, there is also a byte
> swapping CPU mode and byte swapping access instructions. I think only
> the instructions are used (for PCI).
Right, but that is (to a large extent) a separate problem from memory mapped
peripherals. You still have to handle the case where a single TLB entry
covers both ram and a cross-endian device.
Paul
next prev parent reply other threads:[~2010-11-27 10:26 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-25 7:35 [Qemu-devel] [PATCH 00/15] [RFC] MMIO endianness cleanup Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 01/15] exec: introduce endianness swapped mmio Alexander Graf
2010-11-26 23:00 ` Andreas Färber
2010-11-26 23:06 ` Alexander Graf
2010-11-26 23:18 ` Peter Maydell
2010-11-26 23:47 ` Paul Brook
2010-11-27 10:05 ` Blue Swirl
2010-11-27 10:24 ` Paul Brook [this message]
2010-11-28 8:12 ` Gleb Natapov
2010-11-28 11:05 ` Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 02/15] Add endianness as io mem parameter Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 03/15] Make simple io mem handler endian aware Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 04/15] dbdma: Make little endian Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 05/15] pci-host: Delegate bswap to mmio layer Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 06/15] uninorth: Get rid of bswap Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 07/15] e1000: Make little endian Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 08/15] prep: Declare as " Alexander Graf
2010-11-26 21:58 ` Andreas Färber
2010-11-26 22:06 ` Alexander Graf
2010-11-27 0:08 ` Benjamin Herrenschmidt
2010-11-25 7:35 ` [Qemu-devel] [PATCH 09/15] versatile_pci: " Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 10/15] ppc4xx_pci: " Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 11/15] openpic: Replace explicit byte swap with endian hints Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 12/15] rtl8139: Declare as little endian Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 13/15] heathrow_pic: " Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 14/15] isa_mmio: Always use " Alexander Graf
2010-11-25 7:35 ` [Qemu-devel] [PATCH 15/15] usb_ohci: " Alexander Graf
2010-11-25 10:18 ` [Qemu-devel] [PATCH 00/15] [RFC] MMIO endianness cleanup Gerd Hoffmann
2010-11-25 10:23 ` Alexander Graf
2010-11-25 10:42 ` Gleb Natapov
2010-11-25 12:14 ` [Qemu-devel] " Paul Brook
2010-11-26 18:44 ` Blue Swirl
2010-11-26 18:49 ` Alexander Graf
2010-11-27 10:09 ` Avi Kivity
-- strict thread matches above, loose matches on Subject: below --
2010-11-30 14:35 [Qemu-devel] [PATCH 00/15] [PATCH] MMIO endianness cleanup v1 Alexander Graf
2010-11-30 14:35 ` [Qemu-devel] [PATCH 01/15] exec: introduce endianness swapped mmio Alexander Graf
2010-12-08 11:05 [Qemu-devel] [PATCH 00/15] MMIO endianness cleanup v2 Alexander Graf
2010-12-08 11:05 ` [Qemu-devel] [PATCH 01/15] exec: introduce endianness swapped mmio Alexander Graf
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