When running a multi-threaded guest and vcpu 0 in a virtual core
is not running in the guest (i.e. it is busy elsewhere in the host),
thread 0 of the physical core will switch the MMU to the guest and
then go to nap mode in the code at kvm_do_nap. If the guest sends
an IPI to thread 0 using the msgsndp instruction, that will wake
up thread 0 and cause all the threads in the guest to exit to the
host unnecessarily. To avoid the unnecessary exit, this arranges
for the PECEDP bit to be cleared in this situation. When napping
due to a H_CEDE from the guest, we still set PECEDP so that the
thread will wake up on an IPI sent using msgsndp.
Signed-off-by: Paul Mackerras <pau...@samba.org>
---
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index c3b148d..8afc8a8 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -191,6 +191,7 @@ kvmppc_primary_no_guest:
li r3, NAPPING_NOVCPU
stb r3, HSTATE_NAPPING(r13)
+ li r3, 0 /* Don't wake on privileged (OS) doorbell */
b kvm_do_nap
kvm_novcpu_wakeup:
@@ -2107,10 +2108,13 @@ _GLOBAL(kvmppc_h_cede) /* r3 = vcpu pointer,
r11 = msr, r13 = paca */
addi r3, r4, VCPU_TB_CEDE
bl kvmhv_accumulate_time
+ lis r3, LPCR_PECEDP@h /* Do wake on privileged doorbell */
+
/*
* Take a nap until a decrementer or external or doobell interrupt
- * occurs, with PECE1, PECE0 and PECEDP set in LPCR. Also clear the
- * runlatch bit before napping.
+ * occurs, with PECE1 and PECE0 set in LPCR.
+ * On POWER8, if we are ceding, also set PECEDP.
+ * Also clear the runlatch bit before napping.
*/
kvm_do_nap:
mfspr r0, SPRN_CTRLF
@@ -2122,7 +2126,7 @@ kvm_do_nap:
mfspr r5,SPRN_LPCR
ori r5,r5,LPCR_PECE0 | LPCR_PECE1
BEGIN_FTR_SECTION
- oris r5,r5,LPCR_PECEDP@h
+ rlwimi r5, r3, 0, LPCR_PECEDP
END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
mtspr SPRN_LPCR,r5
isync
--
2.1.4
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