From 66feed61cdf6ee65fd551d3460b1efba6bee55b8 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Sat, 28 Mar 2015 14:21:12 +1100 Subject: KVM: PPC: Book3S HV: Use msgsnd for signalling threads on POWER8 This uses msgsnd where possible for signalling other threads within the same core on POWER8 systems, rather than IPIs through the XICS interrupt controller. This includes waking secondary threads to run the guest, the interrupts generated by the virtual XICS, and the interrupts to bring the other threads out of the guest when exiting. Aggregated statistics from debugfs across vcpus for a guest with 32 vcpus, 8 threads/vcore, running on a POWER8, show this before the change: rm_entry: 3387.6ns (228 - 86600, 1008969 samples) rm_exit: 4561.5ns (12 - 3477452, 1009402 samples) rm_intr: 1660.0ns (12 - 553050, 3600051 samples) and this after the change: rm_entry: 3060.1ns (212 - 65138, 953873 samples) rm_exit: 4244.1ns (12 - 9693408, 954331 samples) rm_intr: 1342.3ns (12 - 1104718, 3405326 samples) for a test of booting Fedora 20 big-endian to the login prompt. The time taken for a H_PROD hcall (which is handled in the host kernel) went down from about 35 microseconds to about 16 microseconds with this change. The noinline added to kvmppc_run_core turned out to be necessary for good performance, at least with gcc 4.9.2 as packaged with Fedora 21 and a little-endian POWER8 host. Signed-off-by: Paul Mackerras Signed-off-by: Alexander Graf --- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) (limited to 'arch/powerpc/kvm/book3s_hv_rmhandlers.S') diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index fcf3a617cc8a..4d70df26c402 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -1123,6 +1123,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) cmpwi r12,BOOK3S_INTERRUPT_SYSCALL beq hcall_try_real_mode + /* Hypervisor doorbell - exit only if host IPI flag set */ + cmpwi r12, BOOK3S_INTERRUPT_H_DOORBELL + bne 3f + lbz r0, HSTATE_HOST_IPI(r13) + beq 4f + b guest_exit_cont +3: /* External interrupt ? */ cmpwi r12, BOOK3S_INTERRUPT_EXTERNAL bne+ guest_exit_cont @@ -1135,7 +1142,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) bgt guest_exit_cont /* Check if any CPU is heading out to the host, if so head out too */ - ld r5, HSTATE_KVM_VCORE(r13) +4: ld r5, HSTATE_KVM_VCORE(r13) lwz r0, VCORE_ENTRY_EXIT(r5) cmpwi r0, 0x100 mr r4, r9 @@ -2148,7 +2155,7 @@ _GLOBAL(kvmppc_h_cede) /* r3 = vcpu pointer, r11 = msr, r13 = paca */ /* * Take a nap until a decrementer or external or doobell interrupt * occurs, with PECE1 and PECE0 set in LPCR. - * On POWER8, if we are ceding, also set PECEDP. + * On POWER8, set PECEDH, and if we are ceding, also set PECEDP. * Also clear the runlatch bit before napping. */ kvm_do_nap: @@ -2161,6 +2168,7 @@ kvm_do_nap: mfspr r5,SPRN_LPCR ori r5,r5,LPCR_PECE0 | LPCR_PECE1 BEGIN_FTR_SECTION + ori r5, r5, LPCR_PECEDH rlwimi r5, r3, 0, LPCR_PECEDP END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S) mtspr SPRN_LPCR,r5 @@ -2299,7 +2307,7 @@ machine_check_realmode: * Returns (in r3): * 0 if nothing needs to be done * 1 if something happened that needs to be handled by the host - * -1 if there was a guest wakeup (IPI) + * -1 if there was a guest wakeup (IPI or msgsnd) * * Also sets r12 to the interrupt vector for any interrupt that needs * to be handled now by the host (0x500 for external interrupt), or zero. @@ -2330,7 +2338,15 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S) /* hypervisor doorbell */ 3: li r12, BOOK3S_INTERRUPT_H_DOORBELL + /* see if it's a host IPI */ li r3, 1 + lbz r0, HSTATE_HOST_IPI(r13) + cmpwi r0, 0 + bnelr + /* if not, clear it and return -1 */ + lis r6, (PPC_DBELL_SERVER << (63-36))@h + PPC_MSGCLR(6) + li r3, -1 blr /* -- cgit v1.2.3-55-g7522