Re: [Xen-devel] [PATCH RFC v2 02/12] x86: don't use hypervisor stack size for dumping guest stacks

[Juergen Gross <jgross@xxxxxxxx>]

On 23/01/18 10:26, Jan Beulich wrote:
>>>> On 22.01.18 at 13:32, <jgross@xxxxxxxx> wrote:
>> show_guest_stack() and compat_show_guest_stack() stop dumping the
>> stack of the guest whenever its virtual address reaches the same
>> alignment which is used for the hypervisor stacks.
>>
>> Remove this arbitrary limit and try to dump a fixed number of lines
>> instead.
> 
> Hmm, I can see your point, but before looking at the change in detail
> I think we need to agree on what behavior we want. Dumping
> arbitrary data as if it was a part of the stack isn't very helpful, limiting
> the risk of which is, I think, the reason for the way things currently
> work (assuming that guest kernels won't have stacks larger than Xen
> itself, and that they too would align them). What would perhaps be
> better is for the guest to supply information about the restrictions it
> enforces on its stacks, which Xen could then use here. In the
> absence of such hints using the values currently being used would
> possibly make sense.

Currently the stack dump will have the same fixed number of lines as
with my patch. I'm only removing the premature end of dumping whenever
the stack address crosses a 32kB boundary. Linux 64 bit pv guests are
using 16kB stack size. So using this boundary would be more natural.


Juergen

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