Re: CONFIG_SCRUB_DEBUG=y + arm64 + livepatch = Xen BUG at page_alloc.c:738

[Konrad Rzeszutek Wilk <konrad@kernel.org>]

On Mon, Sep 11, 2017 at 08:45:02PM -0400, Boris Ostrovsky wrote:
> 
> 
> On 09/11/2017 07:55 PM, Konrad Rzeszutek Wilk wrote:
> > Hey,
> > 
> > I've only been able to reproduce this on ARM64 (trying right now ARM32
> > as well), and not on x86.
> > 
> > If I compile Xen without CONFIG_SCRUB_DEBUG it works great. But if
> > enable it and try to load a livepatch it blows up in page_alloc.c:738
> > 
> > This is with origin/staging (d0291f3391)
> 
> Can you still reproduce this if you revert 307c3be?

Sadly yes - it still crashes. I didn't capture the serial output.

I honestly think the issue is that on ARM64 the "sleep" loop does not
wake up as often as on x86 (CC-ing Dariof who I believe observed this
with Credit2 and the wakeup.. something) - maybe he remembers the
details. Anyhow my theory is that the pages are not scrubbed at all
when they go in the idle loop as once it goes to sleep - it stays there.

Ah, see commit 05c52278a7c92bc753d9fe32017e4961012b9f23 

Maybe this is related?
> 
> 
> -boris

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