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Re: [Qemu-devel] [PATCH] 64 bit I/O support v7
From: |
Edgar E. Iglesias |
Subject: |
Re: [Qemu-devel] [PATCH] 64 bit I/O support v7 |
Date: |
Fri, 1 May 2009 18:36:14 +0200 |
User-agent: |
Mutt/1.5.16 (2007-06-09) |
On Fri, May 01, 2009 at 06:51:08PM +0300, Blue Swirl wrote:
> On 5/1/09, Paul Brook <address@hidden> wrote:
> > > > sparc hardware is rather abnormal (for qemu at least) because it cares
> > > > what happens when you use the wrong width. Most devices don't care, and
> > > > having any NULL functions is liable to introduce significant overhead.
> > >
> >
> > > Ok, so that explains the curious code in m48t59.c:
> >
> > >...
> >
> > > So nvram_writeq should be present on non sparc architectures
> > > and actually should be doing 8 byte accesses? How do we handle
> > > architecture differences like this? On sparc, it looks like the
> > > sbus controller does this because the actual hardware really
> > > only has an 8 bit bus.
> >
> >
> > Are there actually any cases where this matters?
> >
> > My guess is that in pactice we only have certain SPARC devices that need to
> > trap when you do a wrong sized access, and for everything else you're told
> > not to do that, and qemu can happily return garbage.
> >
> > If this is the case then the IO_MEM_SUBWIDTH code seems like complete
> > overkill. I reccommend ripping it out, and maybe having the registration
> > function replace NULL with the unassigned hander.
>
> Maybe the registration could also be changed so that if the device
> only cares for (say) 16 bits (and does not want trapping for the wrong
> sized access), the 64, 32 and 8 bit cases are emulated at higher
> level. This would shrink the code base a bit and maybe fits to the bus
> model.
I'd appreciate something along these lines :)
Cheers
- 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, 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 <=
- 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
- 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, 2009/05/02
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Paul Brook, 2009/05/02
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Jamie Lokier, 2009/05/04
- Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Edgar E. Iglesias, 2009/05/05
Re: [Qemu-devel] [PATCH] 64 bit I/O support v7, Robert Reif, 2009/05/01