The nvidiafb driver is requiring too much vmalloc space and other problems.

The nvidiafb driver is requiring too much vmalloc space and other problems.

[Miles Lane]

Hello,

With guidance from Randy Dunlap, it has been determined that
the nvidiafb driver will fail to operate correctly unless more than
128M of memory is provided by using "vmalloc=".  The default 
kernel configuration provides for 128M, but Randy found that:

>I started looking at vmalloc() and what it calls (which is
> __get_vm_area).  _get_vm_area() always allocates one extra
> page (called a "guard page") between all vmalloc allocations,
> so even though 128 MB is the default amount and the amount
> that nvidiafb wants to use, the kernel wants to allocate
> 128 MB + PAGE_SIZE (4 KB on x86; are you on x86?), so even
> if nvidiafb is the only caller, the vmalloc() call will fail.

Booting with vmalloc=256M works, but Andrew thinks that 
nvidiafb should not be requiring 128M in the first place.

Regarding the problems with i2c bit-banging drivers, I don't
know if the Oops I have been getting is related to the vmalloc
issue somehow.  Comments?  I'll try to repro the crash with
vmalloc=256M set.

Lastly, with vmalloc=256M, my machine crashes whenever 
I try to switch from XFree86 to a framebuffer console.  I cannot
see the oops.  Unfortunately, the only machine I could use for
debugging using a serial connection is a Powerbook, which has
no serial port.

I could try setting up dumping the stack over the network,
but I have never tried to do this before and do not know
whether I can do the dump to a Powerbook running OS/X.
Any suggestions?

Thanks,
        Miles


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Re: The nvidiafb driver is requiring too much vmalloc space and other problems.

[Benjamin Herrenschmidt]

On Wed, 2005-03-30 at 14:59 -0800, Miles Lane wrote:
> Hello,
> 
> With guidance from Randy Dunlap, it has been determined that
> the nvidiafb driver will fail to operate correctly unless more than
> 128M of memory is provided by using "vmalloc=".  The default 
> kernel configuration provides for 128M, but Randy found that:

 .../...

it's a problem with ioremap of the framebuffer ? (which uses get_vm_area
as well) or is there an actual vmalloc in there ?

In radeonfb, I had to limit the amount of vram actually ioremap'd by the
kernel because of that.

Ben.




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Re: The nvidiafb driver is requiring too much vmalloc space and other problems.

[Randy.Dunlap]

Benjamin Herrenschmidt wrote:
> On Wed, 2005-03-30 at 14:59 -0800, Miles Lane wrote:
> 
>>Hello,
>>
>>With guidance from Randy Dunlap, it has been determined that
>>the nvidiafb driver will fail to operate correctly unless more than
>>128M of memory is provided by using "vmalloc=".  The default 
>>kernel configuration provides for 128M, but Randy found that:
> 
> 
>  .../...
> 
> it's a problem with ioremap of the framebuffer ? (which uses get_vm_area
> as well) or is there an actual vmalloc in there ?

It's ioremap of the frame buffer -- 128 MB being requested and it
fails if the default 128 MB kernel vmalloc area size is used.

> In radeonfb, I had to limit the amount of vram actually ioremap'd by the
> kernel because of that.

I guess that Tony will know what to do when he sees this....

-- 
~Randy


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