Xen devel - Oct 2005 - RE: DomU panic in net_rx_action *initiated by another DomU*; 7503:20d1a79ebe31

> Pardon me replying to my own post; it was only after hitting 
> "send" on the first one I took a closer look and found a much 
> more interesting (and worrisome) aspect to the issue I''ve 
> been seeing: Another DomU crashed with the same error at the 
> same time. This one was testing an experimental Linux kernel 
> patch (impacting procfs handling of symlinks), and 
> particularly unstable for that reason. It''s interesting, 
> though, that the other DomU (without any such patch applied) 
> appeared to be impacted as well by the same issue.
I think this issue is at least approximately understood, and is present
in all xen x86_64 kernels:

rogue read-only mappings to linux heap pages left over from the
''initial
mapping'' are preventing the netfront driver unmapping pages to hand
over
as rx free buffers. This is compounded by the failure handling path
being slightly borked.

Ian

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Ian Pratt wrote:
> I think this issue is at least approximately understood, and is present
> in all xen x86_64 kernels:
> 
> rogue read-only mappings to linux heap pages left over from the
''initial
> mapping'' are preventing the netfront driver unmapping pages to
hand over
> as rx free buffers. This is compounded by the failure handling path
> being slightly borked.
I''m sorry to be a bother -- but is there any ETA on a fix, or a
bugzilla
entry by which I can track this issue? The only netfront-related checkin 
I see to bugzilla is a fix for bug#183, and that appears to be distinct 
(I''m not getting the "#### netfront can''t alloc rx grant
refs", and so
would appear not to be hitting that code).

This is happening quite frequently for me, even when I''m *not* using
the
kernel with the unstable module which triggers it every time.

If there is no bugzilla entry, I''d be glad to start one -- but since
the
issue is described as already understood, it sounds like there''s likely
already a bug for it that I''m just not seeing.


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On 2 Nov 2005, at 13:54, Charles Duffy wrote:
>> I think this issue is at least approximately understood, and is 
>> present
>> in all xen x86_64 kernels:
>> rogue read-only mappings to linux heap pages left over from the 
>> ''initial
>> mapping'' are preventing the netfront driver unmapping pages to
hand
>> over
>> as rx free buffers. This is compounded by the failure handling path
>> being slightly borked.
>
> I''m sorry to be a bother -- but is there any ETA on a fix, or a 
> bugzilla entry by which I can track this issue? The only 
> netfront-related checkin I see to bugzilla is a fix for bug#183, and 
> that appears to be distinct (I''m not getting the "####
netfront can''t
> alloc rx grant refs", and so would appear not to be hitting that 
> code).
>
> This is happening quite frequently for me, even when I''m *not*
using
> the kernel with the unstable module which triggers it every time.
>
> If there is no bugzilla entry, I''d be glad to start one -- but
since
> the issue is described as already understood, it sounds like
there''s
> likely already a bug for it that I''m just not seeing.
If latest unstable still exhibits this bug, you should definitely open 
a bugzilla entry.

  -- Keir


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