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 <paulus@xxxxxxxxx> --- 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 0a35b8d..35b1847 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: @@ -2128,10 +2129,13 @@ _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 @@ -2143,7 +2147,7 @@ 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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
