On Tue, 13 Jun 2017 23:05:51 +1000
Nicholas Piggin <npig...@gmail.com> wrote:
> Idle code now always runs at the 0xc... effective address whether
> in real or virtual mode. This means rfid can be ditched, along
> with a lot of SRR manipulations.
>
> In the wakeup path, carry SRR1 around in r12. Use mtmsrd to change
> MSR states as required.
>
> This also balances the return prediction for the idle call, by
> doing blr rather than rfid to return to the idle caller.
>
> On POWER9, 2-process context switch on different cores, with snooze
> disabled, increases performance by 2%.
This patch has a few stupid bugs in the kvm_start_guest path. It needs
the following incremental patch.
- mtspr dst/src wrong
- Did not pass SRR1 in r3 to kvm_start_guest
- Didn't take into account the return back to pnv_wakeup_loss, so
r1 was getting lost.
This would cause crashes when starting KVM guests with -smp cores=2,threads=8
I've also tested HMI wakeup by adjusting SRR1 in the simulator, but
can't do an HMI injection on real hardware when it is in nap state
AFAIK.
Thanks,
Nick
---
arch/powerpc/kernel/idle_book3s.S | 10 +++++++---
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 6 ++++--
2 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/kernel/idle_book3s.S
b/arch/powerpc/kernel/idle_book3s.S
index 6305d4d7a268..ebe80b5d5ce4 100644
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -402,16 +402,16 @@ BEGIN_FTR_SECTION
BEGIN_FTR_SECTION_NESTED(70)
bl power9_dd1_recover_paca
END_FTR_SECTION_NESTED_IFSET(CPU_FTR_POWER9_DD1, 70)
- ld r1,PACAR1(r13)
bl pnv_restore_hyp_resource_arch300
FTR_SECTION_ELSE
- ld r1,PACAR1(r13)
bl pnv_restore_hyp_resource_arch207
ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300)
li r0,PNV_THREAD_RUNNING
stb r0,PACA_THREAD_IDLE_STATE(r13) /* Clear thread state */
+ mr r3,r12
+
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
li r0,KVM_HWTHREAD_IN_KERNEL
stb r0,HSTATE_HWTHREAD_STATE(r13)
@@ -425,7 +425,6 @@ ALT_FTR_SECTION_END_IFSET(CPU_FTR_ARCH_300)
#endif
/* Return SRR1 from power7_nap() */
- mr r3,r12
blt cr3,pnv_wakeup_noloss
b pnv_wakeup_loss
@@ -499,6 +498,7 @@ pnv_restore_hyp_resource_arch207:
* r4 - PACA_THREAD_IDLE_STATE
*/
pnv_wakeup_tb_loss:
+ ld r1,PACAR1(r13)
/*
* Before entering any idle state, the NVGPRs are saved in the stack.
* If there was a state loss, or PACA_NAPSTATELOST was set, then the
@@ -789,9 +789,11 @@ fastsleep_workaround_at_exit:
/*
* R3 here contains the value that will be returned to the caller
* of power7_nap.
+ * R12 contains SRR1 for CHECK_HMI_INTERRUPT.
*/
.global pnv_wakeup_loss
pnv_wakeup_loss:
+ ld r1,PACAR1(r13)
BEGIN_FTR_SECTION
CHECK_HMI_INTERRUPT
END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
@@ -809,11 +811,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
/*
* R3 here contains the value that will be returned to the caller
* of power7_nap.
+ * R12 contains SRR1 for CHECK_HMI_INTERRUPT.
*/
pnv_wakeup_noloss:
lbz r0,PACA_NAPSTATELOST(r13)
cmpwi r0,0
bne pnv_wakeup_loss
+ ld r1,PACAR1(r13)
BEGIN_FTR_SECTION
CHECK_HMI_INTERRUPT
END_FTR_SECTION_IFSET(CPU_FTR_HVMODE)
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index eb5b78b6bacf..ecb69c4ee943 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -342,7 +342,7 @@ kvm_start_guest:
* Could avoid this and pass it through in r3. For now,
* code expects it to be in SRR1.
*/
- mtspr r3,SPRN_SRR1
+ mtspr SPRN_SRR1,r3
ld r2,PACATOC(r13)
@@ -462,13 +462,15 @@ kvm_no_guest:
/*
* We jump to pnv_wakeup_loss, which will return to the caller
* of power7_nap in the powernv cpu offline loop. The value we
- * put in r3 becomes the return value for power7_nap.
+ * put in r3 becomes the return value for power7_nap. pnv_wakeup_loss
+ * requires SRR1 in r12.
*/
li r3, LPCR_PECE0
mfspr r4, SPRN_LPCR
rlwimi r4, r3, 0, LPCR_PECE0 | LPCR_PECE1
mtspr SPRN_LPCR, r4
li r3, 0
+ mfspr r12,SPRN_SRR1
b pnv_wakeup_loss
53: HMT_LOW
--
2.11.0
