From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 5/6] ARM: re-implement physical address space switching
Date: Wed, 6 May 2015 17:24:42 +0100 [thread overview]
Message-ID: <20150506162441.GC14922@arm.com> (raw)
In-Reply-To: <20150506161406.GC2974@leverpostej>
On Wed, May 06, 2015 at 05:14:06PM +0100, Mark Rutland wrote:
> > > cr = get_cr();
> > > set_cr(cr & ~(CR_I | CR_C | CR_W));
> > > flush_cache_all();
> > >
> > > With the MMU on at this point the page table walkers can race with the
> > > set/way maintenance. It also relies on the compiler not making stack
> > > accesses between the SCTLR write and the completion of flush_cache_all,
> > > which is likely but not guranteed.
> >
> > Yes, I suppose you're right, but there's really no other way to do
> > this other than coding up CPU specific code.
> >
> > What we'd need to do is to code up a specific assembly routine which
> > disables the I and C control register flags, flushes the cache, jumps
> > to the physical alias and then disables the MMU all without touching
> > memory. That's far too much effort. Like I say, maybe we should just
> > bin Keystone for this crap...
> >
> > I'm not interested in trying to "fix" this code any further - as I
> > said earlier, it took quite a while to get this code working on
> > Keystone, which is really all we care about. Anyone else who copies
> > the abortion that TI made in Keystone should be shot. :)
> >
> > While the community has the luxury of saying "we don't like it, it's
> > TI's problem" - which is what was done when the problems were first
> > pointed out by Will, the net result is that this problem became my
> > problem to try and sort out.
> >
> > So, if you have a better idea how to fix this, I'm all ears.
> >
> > What I'm certain of though is that this is an improvement over what's
> > in the kernel today, and so should go in irrespective of whether it's
> > totally bullet-proof or not.
>
> I don't disagree with that. :)
>
> w.r.t. "better" ideas, my initial thought was that we could move the
> SCTLR.{C,M} clearing into lpae_pgtables_remap_asm, along with a call to
> v7_flush_dcache_all (as it should be in the physical mapping). So long
> as the kernel text was initially clean to the PoC I'd expect that to
> work, but I understood from your initial reply you'd tried that and
> something went wrong.
>
> Perhaps we can look into that later.
I think a comment summarising the conclusion of this thread above the
cache flush and rmk's choice of adjective to describe the keystone SoC
would be sufficient.
Will
next prev parent reply other threads:[~2015-05-06 16:24 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-08 9:44 [PATCH 0/7] Fix Keystone 2 physical address switch Russell King - ARM Linux
2015-04-08 9:45 ` [PATCH 1/6] ARM: keystone2: move platform notifier initialisation into platform init Russell King
2015-04-13 18:57 ` santosh shilimkar
2015-04-08 9:45 ` [PATCH 2/6] ARM: keystone2: move update of the phys-to-virt constants into generic code Russell King
2015-04-08 14:56 ` Grygorii.Strashko@linaro•org
2015-04-08 18:00 ` Russell King - ARM Linux
2015-04-09 14:51 ` Grygorii.Strashko@linaro•org
2015-04-09 15:49 ` Russell King - ARM Linux
2015-04-09 16:15 ` Grygorii.Strashko@linaro•org
2015-04-08 19:19 ` Russell King - ARM Linux
2015-04-13 19:02 ` santosh shilimkar
2015-04-08 9:45 ` [PATCH 3/6] ARM: keystone2: move address space switch printk to " Russell King
2015-04-13 19:02 ` santosh shilimkar
2015-04-08 9:45 ` [PATCH 4/6] ARM: keystone2: rename init_meminfo to pv_fixup Russell King
2015-04-13 19:03 ` santosh shilimkar
2015-04-08 9:45 ` [PATCH 5/6] ARM: re-implement physical address space switching Russell King
2015-04-08 14:34 ` Thomas Petazzoni
2015-04-08 17:27 ` santosh shilimkar
2015-04-08 18:10 ` Russell King - ARM Linux
2015-04-08 17:36 ` Mark Rutland
2015-04-08 17:55 ` Russell King - ARM Linux
2015-04-13 19:11 ` santosh shilimkar
2015-04-15 12:07 ` Mark Rutland
2015-04-15 17:27 ` santosh shilimkar
2015-04-23 11:24 ` Mark Rutland
2015-05-06 10:18 ` Russell King - ARM Linux
2015-05-06 10:37 ` Mark Rutland
2015-05-06 11:33 ` Russell King - ARM Linux
2015-05-06 15:33 ` Mark Rutland
2015-05-06 15:50 ` Russell King - ARM Linux
2015-05-06 16:14 ` Mark Rutland
2015-05-06 16:24 ` Will Deacon [this message]
2015-04-08 9:45 ` [PATCH 6/6] ARM: cleanup early_paging_init() calling Russell King
2015-04-13 19:13 ` santosh shilimkar
2015-04-08 17:21 ` [PATCH 0/7] Fix Keystone 2 physical address switch santosh shilimkar
2015-04-09 16:21 ` Russell King - ARM Linux
2015-04-09 16:35 ` santosh shilimkar
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