Re: [PATCH] sparc64 - strict devmem

[Bob Picco <bpicco@meloft.net>]

Hi,
David Miller wrote:	[Tue Mar 04 2014, 03:46:26PM EST]
> From: Bob Picco <bpicco@meloft.net>
> Date: Mon,  3 Mar 2014 12:00:35 -0500
> 
> > From: bob picco <bpicco@meloft.net>
> > 
> > This patch adds support to enable STRICT_DEVMEM for sparc64. By selecting the
> > new config option you enable this feature.
> > 
> > CC: Sam Ravnborg <sam@ravnborg.org>
> > Signed-off-by: Bob Picco <bob.picco@oracle.com>
> 
> Ok, I looked more deeply into this and I'm going to rescind my request
> to use kern_addr_valid().
Okay.
> 
> This devmem_is_allowed() seems to also want to allow non-RAM MMIO
> accesses too.
Yes, this is my bad. I expected this issue to come up in the first round but
forgot. I wasn't certain general MMIO access via /dev/mem is of value to
sparc64. One could always turn off the config option.
> 
> So using the iomem resource is probably the way to go.
> 
> Two things:
> 
> 1) We have to make sure caching will be disabled and the side-effect
>    bit will be set in accesses to non-RAM pages.
> 
> 2) Our implementation of devmem_is_allowed() should be aligned as
>    much as possible with other implementations.  Perhaps powerpc
>    is the best example to use.
I'll take a peek at powerpc.

thanx and you're welcome,

bob
> 
> Thanks.
> 
> 
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