From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Christophe Leroy <christophe.leroy@c-s.fr>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/32s: Fix CPU wake-up from sleep mode
Date: Tue, 4 Feb 2020 23:01:34 +1100 (AEDT) [thread overview]
Message-ID: <48BjwG5Y3xzB3wq@ozlabs.org> (raw)
In-Reply-To: <6d02c3ae6ad77af34392e98117e44c2bf6d13ba1.1580121710.git.christophe.leroy@c-s.fr>
On Mon, 2020-01-27 at 10:42:04 UTC, Christophe Leroy wrote:
> Commit f7354ccac844 ("powerpc/32: Remove CURRENT_THREAD_INFO and
> rename TI_CPU") broke the CPU wake-up from sleep mode (i.e. when
> _TLF_SLEEPING is set) by delaying the tovirt(r2, r2).
>
> This is because r2 is not restored by fast_exception_return. It used
> to work (by chance ?) because CPU wake-up interrupt never comes from
> user, so r2 is expected to point to 'current' on return.
>
> Commit e2fb9f544431 ("powerpc/32: Prepare for Kernel Userspace Access
> Protection") broke it even more by clobbering r0 which is not
> restored by fast_exception_return either.
>
> Use r6 instead of r0. This is possible because r3-r6 are restored by
> fast_exception_return and only r3-r5 are used for exception arguments.
>
> For r2 it could be converted back to virtual address, but stay on the
> safe side and restore it from the stack instead. It should be live
> in the cache at that moment, so loading from the stack should make
> no difference compared to converting it from phys to virt.
>
> Fixes: f7354ccac844 ("powerpc/32: Remove CURRENT_THREAD_INFO and rename TI_CPU")
> Fixes: e2fb9f544431 ("powerpc/32: Prepare for Kernel Userspace Access Protection")
> Cc: stable@vger.kernel.org
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/9933819099c4600b41a042f27a074470a43cf6b9
cheers
prev parent reply other threads:[~2020-02-04 12:13 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-27 10:42 [PATCH] powerpc/32s: Fix CPU wake-up from sleep mode Christophe Leroy
2020-02-04 12:01 ` Michael Ellerman [this message]
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