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From: Greg KH <gregkh@linuxfoundation.org>
To: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org, Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH] powerpc/powernv : Save/Restore SPRG3 on entry/exit from stop.
Date: Mon, 23 Jul 2018 08:16:28 +0200	[thread overview]
Message-ID: <20180723061628.GA2035@kroah.com> (raw)
In-Reply-To: <1532323855-25307-1-git-send-email-ego@linux.vnet.ibm.com>

On Mon, Jul 23, 2018 at 11:00:55AM +0530, Gautham R. Shenoy wrote:
> From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com>
> 
> [ Upstream commit b03897cf318dfc47de33a7ecbc7655584266f034 ]
> 
> On 64-bit servers, SPRN_SPRG3 and its userspace read-only mirror
> SPRN_USPRG3 are used as userspace VDSO write and read registers
> respectively.
> 
> SPRN_SPRG3 is lost when we enter stop4 and above, and is currently not
> restored.  As a result, any read from SPRN_USPRG3 returns zero on an
> exit from stop4 and above.
> 
> Thus in this situation, on POWER9, any call from sched_getcpu() always
> returns zero, as on powerpc, we call __kernel_getcpu() which relies
> upon SPRN_USPRG3 to report the CPU and NUMA node information.
> 
> Fix this by restoring SPRN_SPRG3 on wake up from a deep stop state
> with the sprg_vdso value that is cached in PACA.
> 
> Fixes: e1c1cfed5432 ("powerpc/powernv: Save/Restore additional SPRs
> for stop4 cpuidle")
> 
> Reported-by: Florian Weimer <fweimer@redhat.com>
> Cc: <stable@vger.kernel.org> # 4.14
> Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
> Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> ---
>  arch/powerpc/kernel/idle_book3s.S | 2 ++
>  1 file changed, 2 insertions(+)

What stable tree(s) do you want this applied to?

thanks,

greg k-h

  reply	other threads:[~2018-07-23  7:16 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-22 16:33 FAILED: patch "[PATCH] powerpc/powernv: Fix save/restore of SPRG3 on entry/exit from" failed to apply to 4.14-stable tree gregkh
2018-07-23  5:30 ` [PATCH] powerpc/powernv : Save/Restore SPRG3 on entry/exit from stop Gautham R. Shenoy
2018-07-23  6:16   ` Greg KH [this message]
2018-07-23  7:53     ` Greg KH
2018-07-23 12:13       ` Gautham R Shenoy
  -- strict thread matches above, loose matches on Subject: below --
2018-07-17 11:27 Gautham R. Shenoy
2018-07-17 11:47 ` Gautham R Shenoy

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