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authorGautham R. Shenoy <ego@linux.vnet.ibm.com>2018-07-18 10:33:16 +0200
committerMichael Ellerman <mpe@ellerman.id.au>2018-07-18 12:40:17 +0200
commitb03897cf318dfc47de33a7ecbc7655584266f034 (patch)
tree4e333d4a50a428b4f7b01dc478487d22b630ad96
parentpowerpc/Makefile: Assemble with -me500 when building for E500 (diff)
downloadlinux-b03897cf318dfc47de33a7ecbc7655584266f034.tar.xz
linux-b03897cf318dfc47de33a7ecbc7655584266f034.zip
powerpc/powernv: Fix save/restore of SPRG3 on entry/exit from stop (idle)
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>
-rw-r--r--arch/powerpc/kernel/idle_book3s.S2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index e734f6e45abc..689306118b48 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -144,7 +144,9 @@ power9_restore_additional_sprs:
mtspr SPRN_MMCR1, r4
ld r3, STOP_MMCR2(r13)
+ ld r4, PACA_SPRG_VDSO(r13)
mtspr SPRN_MMCR2, r3
+ mtspr SPRN_SPRG3, r4
blr
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