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| author | Gautham R. Shenoy <ego@linux.vnet.ibm.com> | 2018-07-18 14:03:16 +0530 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-07-25 11:25:11 +0200 |
| commit | ff42682f21d7084e0808171a973b0bcecd14ec14 (patch) | |
| tree | 76ed3d933a21f8c27c71623c86e1d926fbfa5d35 | |
| parent | ea8a50e5f829ad3e855f45b29e96612a92bb1418 (diff) | |
powerpc/powernv: Fix save/restore of SPRG3 on entry/exit from stop (idle)
commit b03897cf318dfc47de33a7ecbc7655584266f034 upstream.
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 (Power9 only) 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")
Cc: stable@vger.kernel.org # v4.14+
Reported-by: Florian Weimer <fweimer@redhat.com>
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/powerpc/kernel/idle_book3s.S | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S index e35cebd45c35..4efbde0984b2 100644 --- a/arch/powerpc/kernel/idle_book3s.S +++ b/arch/powerpc/kernel/idle_book3s.S @@ -140,6 +140,8 @@ power9_restore_additional_sprs: ld r4, STOP_MMCR2(r13) mtspr SPRN_MMCR1, r3 mtspr SPRN_MMCR2, r4 + ld r4, PACA_SPRG_VDSO(r13) + mtspr SPRN_SPRG3, r4 blr /* |