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Shenoy" To: Michael Ellerman , Benjamin Herrenschmidt , Michael Neuling , Vaidyanathan Srinivasan Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Florian Weimer , "Gautham R. Shenoy" , Oleg Nesterov Subject: [PATCH] powerpc/powernv : Save/Restore SPRG3 on entry/exit from stop. Date: Tue, 17 Jul 2018 16:57:29 +0530 X-Mailer: git-send-email 1.8.3.1 X-TM-AS-GCONF: 00 x-cbid: 18071711-0068-0000-0000-000003195B7D X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009379; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01062049; UDB=6.00545287; IPR=6.00839954; MB=3.00022167; MTD=3.00000008; XFM=3.00000015; UTC=2018-07-17 11:27:43 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18071711-0069-0000-0000-0000450FD9BB Message-Id: <1531826849-31838-1-git-send-email-ego@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-07-17_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1807170119 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Gautham R. Shenoy" 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, 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 saving the SPRN_SPRG3 before entering a deep stop state, and restoring it back on wakeup from the stop state. Reported-by: Florian Weimer Cc: Oleg Nesterov Cc: Michael Neuling Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Vaidyanathan Srinivasan Signed-off-by: Gautham R. Shenoy --- arch/powerpc/include/asm/cpuidle.h | 1 + arch/powerpc/kernel/asm-offsets.c | 1 + arch/powerpc/kernel/idle_book3s.S | 5 +++++ 3 files changed, 7 insertions(+) diff --git a/arch/powerpc/include/asm/cpuidle.h b/arch/powerpc/include/asm/cpuidle.h index e210a83..03fa904 100644 --- a/arch/powerpc/include/asm/cpuidle.h +++ b/arch/powerpc/include/asm/cpuidle.h @@ -77,6 +77,7 @@ struct stop_sprs { u64 mmcr1; u64 mmcr2; u64 mmcra; + u64 sprg3; }; extern u32 pnv_fastsleep_workaround_at_entry[]; diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 89cf155..a35ebfc 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -776,6 +776,7 @@ int main(void) STOP_SPR(STOP_MMCR1, mmcr1); STOP_SPR(STOP_MMCR2, mmcr2); STOP_SPR(STOP_MMCRA, mmcra); + STOP_SPR(STOP_SPRG3, sprg3); #endif DEFINE(PPC_DBELL_SERVER, PPC_DBELL_SERVER); diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S index d85d551..5069d42 100644 --- a/arch/powerpc/kernel/idle_book3s.S +++ b/arch/powerpc/kernel/idle_book3s.S @@ -120,6 +120,9 @@ power9_save_additional_sprs: mfspr r4, SPRN_MMCR2 std r3, STOP_MMCR1(r13) std r4, STOP_MMCR2(r13) + + mfspr r3, SPRN_SPRG3 + std r3, STOP_SPRG3(r13) blr power9_restore_additional_sprs: @@ -144,7 +147,9 @@ power9_restore_additional_sprs: mtspr SPRN_MMCR1, r4 ld r3, STOP_MMCR2(r13) + ld r4, STOP_SPRG3(r13) mtspr SPRN_MMCR2, r3 + mtspr SPRN_SPRG3, r4 blr /* -- 1.9.4