| Message ID | 1531826849-31838-1-git-send-email-ego@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | powerpc/powernv : Save/Restore SPRG3 on entry/exit from stop. | expand |
On Tue, Jul 17, 2018 at 04:57:29PM +0530, 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, any call from sched_getcpu() always returns This happens only on POWER9. > 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. > I forgot to add that this fixes commit e1c1cfed5432 ("powerpc/powernv: Save/Restore additional SPRs for stop4 cpuidle"). @mpe, do you want me to send fresh patch with these updates ? > Reported-by: Florian Weimer <fweimer@redhat.com> > 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> > --- > 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 >
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 /*