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Re: [Qemu-devel] [PATCH 01/15] exec: introduce endianness swapped mmio
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [PATCH 01/15] exec: introduce endianness swapped mmio |
Date: |
Sat, 27 Nov 2010 10:24:00 +0000 |
User-agent: |
KMail/1.13.5 (Linux/2.6.36-trunk-amd64; KDE/4.4.5; x86_64; ; ) |
> > 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
- [Qemu-devel] [PATCH 03/15] Make simple io mem handler endian aware, (continued)
- [Qemu-devel] [PATCH 03/15] Make simple io mem handler endian aware, Alexander Graf, 2010/11/25
- [Qemu-devel] [PATCH 06/15] uninorth: Get rid of bswap, Alexander Graf, 2010/11/25
- [Qemu-devel] [PATCH 07/15] e1000: Make little endian, Alexander Graf, 2010/11/25
- [Qemu-devel] [PATCH 12/15] rtl8139: Declare as little endian, Alexander Graf, 2010/11/25
- [Qemu-devel] [PATCH 01/15] exec: introduce endianness swapped mmio, Alexander Graf, 2010/11/25
- Re: [Qemu-devel] [PATCH 01/15] exec: introduce endianness swapped mmio, Gleb Natapov, 2010/11/28
[Qemu-devel] [PATCH 05/15] pci-host: Delegate bswap to mmio layer, Alexander Graf, 2010/11/25
[Qemu-devel] [PATCH 13/15] heathrow_pic: Declare as little endian, Alexander Graf, 2010/11/25
[Qemu-devel] [PATCH 11/15] openpic: Replace explicit byte swap with endian hints, Alexander Graf, 2010/11/25
[Qemu-devel] [PATCH 15/15] usb_ohci: Always use little endian, Alexander Graf, 2010/11/25
[Qemu-devel] [PATCH 08/15] prep: Declare as little endian, Alexander Graf, 2010/11/25