Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [v2] powerpc/powernv : Save/Restore SPRG3 on entry/exit from stop. | Date | Thu, 19 Jul 2018 16:06:10 +1000 (AEST) |
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On Wed, 2018-07-18 at 08:33:16 UTC, "Gautham R. Shenoy" wrote: > From: "Gautham R. Shenoy" <ego@linux.vnet.ibm.com> > > 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 > Cc: Oleg Nesterov <oleg@redhat.com> > Cc: Michael Neuling <mikey@neuling.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> > Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Applied to powerpc fixes, thanks.
https://git.kernel.org/powerpc/c/b03897cf318dfc47de33a7ecbc7655
cheers
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