[Xen-devel] Help? Red Hat fails, Suse/Debian both work fine

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

Hi all --

We are seeing a strange problem where a recent cset causes
Red Hat to fail domU boot on ia64 complaining of a hotplug
problem but doesn't cause any problem for Suse or Debian.
It is likely some subtle difference (or bug), perhaps in mmap?
Suggestions/advice from anyone more familiar with distro
differences (on ia64) would be appreciated.

Changeset is xen-unstable 8783 ("Use /dev/kmem to map dom0
xenstore page instead of abusing the foreign mapping interface.",
Feb 8, committed by Christian).  Backing out this changeset
or using the small patch below causes the problem to go away,
so we have a workaround, but a root cause would be nice
to know and fix.

Full thread of discussion can be found here:
http://lists.xensource.com/archives/html/xen-ia64-devel/2006-02/msg00104
.html

Thanks,
Dan

> -----Original Message-----
> From: Akio Takebe [mailto:takebe_akio@xxxxxxxxxxxxxx] 
> Sent: Tuesday, February 28, 2006 2:47 AM
> To: Magenheimer, Dan (HP Labs Fort Collins); yo.fujita; 
> xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> Cc: Akio Takebe
> Subject: RE: [Xen-ia64-devel] Weekly benchmark results [2/3rd week]
> 
> Hi, Dan
> 
> I'm still debuging, but it is very difficult...
> Much advice is welcome. :-)
> 
> Now I can boot domU by using the following patch.
> 
> diff -r 6c43118bdba8 tools/xenstore/xenstored_domain.c
> --- a/tools/xenstore/xenstored_domain.c Fri Feb 24 15:41:08 2006 -0700
> +++ b/tools/xenstore/xenstored_domain.c Tue Feb 28 18:20:16 2006 +0900
> @@ -467,6 +467,7 @@ static int dom0_init(void)
>         int rc, fd;
>         evtchn_port_t port; 
>         unsigned long kva; 
> +       unsigned long mfn; 
>         char str[20]; 
>         struct domain *dom0; 
>  
> @@ -500,9 +501,16 @@ static int dom0_init(void)
>         if (fd == -1)
>                 return -1;
>  
> -       dom0->interface = mmap(NULL, getpagesize(), 
> PROT_READ|PROT_WRITE,
> -                              MAP_SHARED, fd, kva);
> -       if (dom0->interface == MAP_FAILED)
> +       mfn=((0x0fffffffffffffff & kva) >>14);
> +/*
> +        dom0->interface = mmap(NULL, getpagesize(), 
> PROT_READ|PROT_WRITE,
> +                               MAP_SHARED, fd, kva);
> +*/
> +       dom0->interface = xc_map_foreign_range(
> +               *xc_handle, 0,
> +               getpagesize(), PROT_READ|PROT_WRITE, mfn);
> +       if (!dom0->interface) 
> +//     if (dom0->interface == MAP_FAILED)
>                 goto outfd;
>  
>         close(fd);
> 
> Best Regards,
> 
> Akio Takebe
> 
> >Hi Akio --
> >
> >Any more progress on this issue?  If you are stuck,
> >maybe we should post the problem to xen-devel to
> >see if we can get help from a Red Hat person (since
> >the problem doesn't occur on Suse or Debian).
> >
> >Thanks,
> >Dan 
> >
> >> -----Original Message-----
> >> From: Akio Takebe [mailto:takebe_akio@xxxxxxxxxxxxxx] 
> >> Sent: Thursday, February 23, 2006 8:45 PM
> >> To: Magenheimer, Dan (HP Labs Fort Collins); yo.fujita; 
> >> xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
> >> Cc: Akio Takebe
> >> Subject: RE: [Xen-ia64-devel] Weekly benchmark results [2/3rd week]
> >> 
> >> Hi, Dan and Alex
> >> 
> >> I think this issue is only on ia64.
> >> I seem that kmem_map@drivers/char/mem.c is used on ia64, 
> >> but mem_map@drivers/xen/char/mem.c is used on x86.
> >> So I think pfn or kva aren't set correctly.
> >> We tried to boot domU with revesing cset xen-ia64-ustable.8790 
> >> and it was good work.
> >> 
> >> I'm still debugging it. :-<
> >> 
> >> Best Regards,
> >> 
> >> Akio Takebe
> >> 
> >> >Confirmed cset xen-unstable 8783 fails while 8782 succeeds.
> >> >
> >> >Perhaps there's something different about mmap on RH
> >> >vs Suse and Debian?  Perhaps only on ia64?
> >> >
> >> 
> >> 
> >> 
> 
> 
> 

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