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Re: [Xen-devel] Userspace PIO access under xen

To: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] Userspace PIO access under xen
From: "Michael S. Tsirkin" <mst@xxxxxxxxxxxxxx>
Date: Mon, 25 Jul 2005 15:11:35 +0300
Cc: Dror Goldenberg <gdror@xxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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Quoting r. Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>:
> Subject: RE: [Xen-devel] Userspace PIO access under xen
> > The following simple program (below) mmaps PCI I/O memory 
> > into userspace. This works fine under linux, but not in Xen dom0.
> > 
> > Linux:
> > 
> > # ./test1 /sys/bus/pci/devices/0000\:07\:00.0/resource0 0 0 0
> > 
> > Xen dom0:
> > 
> > # ./test1 /sys/bus/pci/devices/0000\:07\:00.0/resource0 0 0 0xf000eef3
> Interesting -- I didn't know you could use /sys/bus/pci/devices/ for
> mapping memory.

You can also use /proc/bus/pci/ for this, the difference is that
you have to give full bus address to /proc/bus/pci/ , while
/sys/bus/pci/devices/ needs an offset within the resource.

> Change pci_mmap_page_range in arch/xen/arch/pci/i386.c to use
> io_remap_pfn_range

I've written a small kernel module to map PIO to userspace
using remap_page_range, and that doesnt seem to work, either.

> I'll check something in.
> Ian

OK, let me know.


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