Re: [Xen-devel] mmap in PV xen-4.0.1

[Ranjith Ravi <ranjith.ravi@xxxxxxxxx>]

> Looking into the kernel source, a check in range_is_allowed failed so

> I just can't map /dev/mem with specified range (-EPERM).

 mmap() and read access  works on 2.6.37.6 

( dom0 - fc13 xen 4.0.2)

Tried it after disabling 'CONFIG_STRICT_DEVMEM' in kernel config.

Can someone point out the changes/patches in 2.6.37.6 which fixes mmap() problem ?

Thanks

Ranjith

On Fri, Aug 12, 2011 at 10:20 AM, Eric Camachat <eric.camachat@xxxxxxxxx> wrote:

On Thu, Aug 11, 2011 at 9:26 PM, Wei Liu <liuw@xxxxxxxxx> wrote:
> On Thu, Aug 11, 2011 at 10:11:20AM -0700, Eric Camachat wrote:
>>
>> Let us back to my original concern:
>> Why remap_pfn_range() woks with my own device node, but deesn't work
>> with /dev/mem node?
>> This behavior is confused me.
>>
>> /Eric
>
> Well, I slightly modify your code -- remove the ioctl and hardcoded
> *base into mapper, and run on my box in dom0 (Xen 4.2 + 2.6.39 PVOPS),
> I get following output and kernel log:
>
> paddr = 0x6d368000
>  mem = 0xffffffffffffffff
>  map = 0x7fa928e88000
> map[0]= 1234
> map[1]= abcd
>
> [  405.039120] memtest: registering /dev/memtest (886)
> [  405.039125] memtest: size of phys_addr_t is 8 bytes
> [  405.039132] memtest: _vbase = 0xffff88006d368000
> [  405.039134] memtest: _pbase = 0x6d368000
> [  405.039135] memtest: _mbase = 0x6fbaa000
> [  781.414747] Program mapper tried to access /dev/mem between 6d368000->6d36c000.
> [  781.414764] memtest_vma_open: virt 0x7f327a275000, phys 0x6d368000
> [  781.414942] mapper[2744]: segfault at ffffffffffffffff ip 00000000004008d7 sp 00007fff233638e0 error 4 in mapper[400000+1000]
> [  781.415064] memtest_vma_close
> [  891.350796] Program mapper tried to access /dev/mem between 6d368000->6d36c000.
> [  891.350813] memtest_vma_open: virt 0x7fa928e88000, phys 0x6d368000
> [  891.350987] mapper[2811]: segfault at ffffffffffffffff ip 00000000004008d7 sp 00007fffc154efd0 error 4 in mapper[400000+1000]
> [  891.351102] memtest_vma_close
>
> Looking into the kernel source, a check in range_is_allowed failed so
> I just can't map /dev/mem with specified range (-EPERM).
>
> But please note that my output of map[0] and map[1] are correct, while
> your output is not correct ('4C4C4C4C'), which you ignored

That's I memset() 'L' to _vbase. Sorry, I pasted wrong output.

> previously. Why not make sure your mapper works correctly? Or can you
> try newer kernel and Xen?
>
> Wei.
>

It works with newer kernel (like 2.6.37), so I think its not XEN's problem.
Thanks for your help!

/Eric

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