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Re: [Qemu-devel] [PATCH] 64 bit I/O support v7
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] [PATCH] 64 bit I/O support v7 |
Date: |
Fri, 1 May 2009 15:14:20 +0100 |
User-agent: |
KMail/1.9.9 |
> The right way to do this is to convert the whole tree at once
> so we don't need the helper functions and two versions of
> cpu_register_io_memory.
> 95% of the hardware drivers could be trivially converted and
> work fine.
I think you're missing my point. It's the 95% of drivers that I don't want to
have to "convert". I'm working on the assumption that devices that actually
implement 64-bit transfers are the exception rather than the rule.
So we have three options:
1) Omit the 64-bit handler for most devices. This will trigger the subwith
code and associated overhead for no good reason[1].
2) Implement a 64-bit handler for every single device. 90% of these are going
to be identical trivial wrappers round the 32-bit function. Maybe 5% actually
need 64-bit accesses, and 5% are broken because someone messed up a
copy/paste.
3) Implement splitting of 64-bit accesses in generic code. Devices that
actually care about 64-bit accesses can install a handler. Everything else
indicates that it wants accesses split, either by a magic handler or a
different registration function.
Your current patch implements a broken version of (3), with a vague hope that
we'll switch to (2) at some time in the future.
I'm suggesting we implement (3) properly from the start.
Paul
[1] I still don't understand why the subwidth code exists, It's seems rather
unlikely we'll have two different devices responding to different types of
access the same address range. That's a separate argument though.
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Paul Brook, 2009/05/01
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Robert Reif, 2009/05/01
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7,
Paul Brook <=
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Robert Reif, 2009/05/01
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Paul Brook, 2009/05/01
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Robert Reif, 2009/05/01
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Paul Brook, 2009/05/01
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Blue Swirl, 2009/05/01
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Edgar E. Iglesias, 2009/05/01
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Robert Reif, 2009/05/01
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Robert Reif, 2009/05/01
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Paul Brook, 2009/05/01
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Robert Reif, 2009/05/01