From mboxrd@z Thu Jan  1 00:00:00 1970
From: Will Deacon <will.deacon@arm.com>
Subject: Re: [ghes_copy_tofrom_phys] BUG: sleeping function called from
 invalid context at mm/page_alloc.c:4150
Date: Mon, 30 Oct 2017 17:49:53 +0000
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To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@suse.de>, Len Brown <lenb@kernel.org>, Tony Luck <tony.luck@intel.com>, Fengguang Wu <fengguang.wu@intel.com>, Tyler Baicar <tbaicar@codeaurora.org>, Huang Ying <ying.huang@intel.com>, Chen Gong <gong.chen@linux.intel.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, "Rafael J. Wysocki" <rjw@rjwysocki.net>, Linux ACPI <linux-acpi@vger.kernel.org>

On Mon, Oct 30, 2017 at 10:46:31AM -0700, Linus Torvalds wrote:
> On Mon, Oct 30, 2017 at 10:20 AM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > I will add a "might_sleep()" to ioremap_page_range() itself, so that
> > we get this warning more reliably and much eailer. Right now it has
> > been hidden by the fact that most of the time the time the page tables
> > may be already allocated, but even then it's broken.
> 
> Done. It doesn't report anything for me, so _hopefully_ the GHES
> driver is the only one that does games like this. See commit
> b39ab98e2f47 ("Mark 'ioremap_page_range()' as possibly sleeping").
> 
> So now it should hopefully warn about this bad usage of page remapping
> reliably, at least if you have CONFIG_DEBUG_ATOMIC_SLEEP enabled.
> 
> Can somebody who has a working GHES setup (although Borislav seems to
> think no such thing exists) verify?
> 
> This obviously won't _fix_ anything, but at least it should make it
> clear it's not that recent change that broke things - that just
> happened to expose it. And hopefully somebody who knows that driver
> will do the proper fixmap thing (or just ioremap once at probe time,
> rather than at run-time).

FWIW, we discussed some of this back in 2015, because the TLB invalidation
looks busted to me too:

https://marc.info/?l=linux-kernel&m=145009681808308&w=2

Didn't go anywhere though...

Will