POWER9 replaces the various power-saving mode instructions on POWER8
(doze, nap, sleep and rvwinkle) with a single "stop" instruction, plus
a register, PSSCR, which controls the depth of the power-saving mode.
This replaces the use of the nap instruction when threads are idle
during guest execution with the stop instruction, and adds code to
set PSSCR to a value which will allow an SMT mode switch while the
thread is idle (given that the core as a whole won't be idle in these
cases).
Signed-off-by: Paul Mackerras <pau...@ozlabs.org>
---
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 29 ++++++++++++++++++-----------
1 file changed, 18 insertions(+), 11 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index acae5c3..e9eaff4 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -501,17 +501,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
cmpwi r0, 0
beq 57f
li r3, (LPCR_PECEDH | LPCR_PECE0) >> 4
- mfspr r4, SPRN_LPCR
- rlwimi r4, r3, 4, (LPCR_PECEDP | LPCR_PECEDH | LPCR_PECE0 | LPCR_PECE1)
- mtspr SPRN_LPCR, r4
- isync
- std r0, HSTATE_SCRATCH0(r13)
- ptesync
- ld r0, HSTATE_SCRATCH0(r13)
-1: cmpd r0, r0
- bne 1b
- nap
- b .
+ mfspr r5, SPRN_LPCR
+ rlwimi r5, r3, 4, (LPCR_PECEDP | LPCR_PECEDH | LPCR_PECE0 | LPCR_PECE1)
+ b kvm_nap_sequence
57: li r0, 0
stbx r0, r3, r4
@@ -2256,6 +2248,17 @@ BEGIN_FTR_SECTION
ori r5, r5, LPCR_PECEDH
rlwimi r5, r3, 0, LPCR_PECEDP
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
+
+kvm_nap_sequence: /* desired LPCR value in r5 */
+BEGIN_FTR_SECTION
+ /*
+ * PSSCR bits: exit criterion = 1 (wakeup based on LPCR at sreset)
+ * enable state loss = 1 (allow SMT mode switch)
+ * requested level = 0 (just stop dispatching)
+ */
+ lis r3, (PSSCR_EC | PSSCR_ESL)@h
+ mtspr SPRN_PSSCR, r3
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
mtspr SPRN_LPCR,r5
isync
li r0, 0
@@ -2264,7 +2267,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
ld r0, HSTATE_SCRATCH0(r13)
1: cmpd r0, r0
bne 1b
+BEGIN_FTR_SECTION
nap
+FTR_SECTION_ELSE
+ PPC_STOP
+ALT_FTR_SECTION_END_IFCLR(CPU_FTR_ARCH_300)
b .
33: mr r4, r3
--
2.7.4
