From ccc07772c99befeda7a7a4b1d05a6f3b762518c2 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Sat, 28 Mar 2015 14:21:07 +1100 Subject: [PATCH] KVM: PPC: Book3S HV: Don't wake thread with no vcpu on guest IPI 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 Signed-off-by: Alexander Graf --- 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 6716db3f1a2b..12d7e4c8dc54 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: @@ -2129,10 +2130,13 @@ _GLOBAL(kvmppc_h_cede) /* r3 = vcpu pointer, r11 = msr, r13 = paca */ bl kvmhv_accumulate_time #endif + 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 @@ -2144,7 +2148,7 @@ 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 -- 2.20.1