From: Paul Mackerras <paulus@samba.org> To: kvm-ppc@vger.kernel.org, kvm@vger.kernel.org Cc: Alexander Graf <agraf@suse.de> Subject: [PATCH 08/12] KVM: PPC: Book3S HV: Use decrementer to wake napping threads Date: Fri, 27 Mar 2015 14:29:52 +1100 [thread overview] Message-ID: <1427426996-17651-9-git-send-email-paulus@samba.org> (raw) In-Reply-To: <1427426996-17651-1-git-send-email-paulus@samba.org> This arranges for threads that are napping due to their vcpu having ceded or due to not having a vcpu to wake up at the end of the guest's timeslice without having to be poked with an IPI. We do that by arranging for the decrementer to contain a value no greater than the number of timebase ticks remaining until the end of the timeslice. In the case of a thread with no vcpu, this number is in the hypervisor decrementer already. In the case of a ceded vcpu, we use the smaller of the HDEC value and the DEC value. Using the DEC like this when ceded means we need to save and restore the guest decrementer value around the nap. Signed-off-by: Paul Mackerras <paulus@samba.org> --- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 43 +++++++++++++++++++++++++++++++-- 1 file changed, 41 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index 35b1847..bc2ab3d 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -172,6 +172,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S) kvmppc_primary_no_guest: /* We handle this much like a ceded vcpu */ + /* put the HDEC into the DEC, since HDEC interrupts don't wake us */ + mfspr r3, SPRN_HDEC + mtspr SPRN_DEC, r3 /* set our bit in napping_threads */ ld r5, HSTATE_KVM_VCORE(r13) lbz r7, HSTATE_PTID(r13) @@ -223,6 +226,12 @@ kvm_novcpu_wakeup: cmpdi r3, 0 bge kvm_novcpu_exit + /* See if our timeslice has expired (HDEC is negative) */ + mfspr r0, SPRN_HDEC + li r12, BOOK3S_INTERRUPT_HV_DECREMENTER + cmpwi r0, 0 + blt kvm_novcpu_exit + /* Got an IPI but other vcpus aren't yet exiting, must be a latecomer */ ld r4, HSTATE_KVM_VCPU(r13) cmpdi r4, 0 @@ -1492,10 +1501,10 @@ kvmhv_do_exit: /* r12 = trap, r13 = paca */ cmpwi r3,0x100 /* Are we the first here? */ bge 43f cmpwi r12,BOOK3S_INTERRUPT_HV_DECREMENTER - beq 40f + beq 43f li r0,0 mtspr SPRN_HDEC,r0 -40: + /* * Send an IPI to any napping threads, since an HDEC interrupt * doesn't wake CPUs up from nap. @@ -2123,6 +2132,27 @@ _GLOBAL(kvmppc_h_cede) /* r3 = vcpu pointer, r11 = msr, r13 = paca */ /* save FP state */ bl kvmppc_save_fp + /* + * Set DEC to the smaller of DEC and HDEC, so that we wake + * no later than the end of our timeslice (HDEC interrupts + * don't wake us from nap). + */ + mfspr r3, SPRN_DEC + mfspr r4, SPRN_HDEC + mftb r5 + cmpw r3, r4 + ble 67f + mtspr SPRN_DEC, r4 +67: + /* save expiry time of guest decrementer */ + extsw r3, r3 + add r3, r3, r5 + ld r4, HSTATE_KVM_VCPU(r13) + ld r5, HSTATE_KVM_VCORE(r13) + ld r6, VCORE_TB_OFFSET(r5) + subf r3, r6, r3 /* convert to host TB value */ + std r3, VCPU_DEC_EXPIRES(r4) + #ifdef CONFIG_KVM_BOOK3S_HV_EXIT_TIMING ld r4, HSTATE_KVM_VCPU(r13) addi r3, r4, VCPU_TB_CEDE @@ -2180,6 +2210,15 @@ kvm_end_cede: /* load up FP state */ bl kvmppc_load_fp + /* Restore guest decrementer */ + ld r3, VCPU_DEC_EXPIRES(r4) + ld r5, HSTATE_KVM_VCORE(r13) + ld r6, VCORE_TB_OFFSET(r5) + add r3, r3, r6 /* convert host TB to guest TB value */ + mftb r7 + subf r3, r7, r3 + mtspr SPRN_DEC, r3 + /* Load NV GPRS */ ld r14, VCPU_GPR(R14)(r4) ld r15, VCPU_GPR(R15)(r4) -- 2.1.4
WARNING: multiple messages have this Message-ID (diff)
From: Paul Mackerras <paulus@samba.org> To: kvm-ppc@vger.kernel.org, kvm@vger.kernel.org Cc: Alexander Graf <agraf@suse.de> Subject: [PATCH 08/12] KVM: PPC: Book3S HV: Use decrementer to wake napping threads Date: Fri, 27 Mar 2015 03:29:52 +0000 [thread overview] Message-ID: <1427426996-17651-9-git-send-email-paulus@samba.org> (raw) In-Reply-To: <1427426996-17651-1-git-send-email-paulus@samba.org> This arranges for threads that are napping due to their vcpu having ceded or due to not having a vcpu to wake up at the end of the guest's timeslice without having to be poked with an IPI. We do that by arranging for the decrementer to contain a value no greater than the number of timebase ticks remaining until the end of the timeslice. In the case of a thread with no vcpu, this number is in the hypervisor decrementer already. In the case of a ceded vcpu, we use the smaller of the HDEC value and the DEC value. Using the DEC like this when ceded means we need to save and restore the guest decrementer value around the nap. Signed-off-by: Paul Mackerras <paulus@samba.org> --- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 43 +++++++++++++++++++++++++++++++-- 1 file changed, 41 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S index 35b1847..bc2ab3d 100644 --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S @@ -172,6 +172,9 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S) kvmppc_primary_no_guest: /* We handle this much like a ceded vcpu */ + /* put the HDEC into the DEC, since HDEC interrupts don't wake us */ + mfspr r3, SPRN_HDEC + mtspr SPRN_DEC, r3 /* set our bit in napping_threads */ ld r5, HSTATE_KVM_VCORE(r13) lbz r7, HSTATE_PTID(r13) @@ -223,6 +226,12 @@ kvm_novcpu_wakeup: cmpdi r3, 0 bge kvm_novcpu_exit + /* See if our timeslice has expired (HDEC is negative) */ + mfspr r0, SPRN_HDEC + li r12, BOOK3S_INTERRUPT_HV_DECREMENTER + cmpwi r0, 0 + blt kvm_novcpu_exit + /* Got an IPI but other vcpus aren't yet exiting, must be a latecomer */ ld r4, HSTATE_KVM_VCPU(r13) cmpdi r4, 0 @@ -1492,10 +1501,10 @@ kvmhv_do_exit: /* r12 = trap, r13 = paca */ cmpwi r3,0x100 /* Are we the first here? */ bge 43f cmpwi r12,BOOK3S_INTERRUPT_HV_DECREMENTER - beq 40f + beq 43f li r0,0 mtspr SPRN_HDEC,r0 -40: + /* * Send an IPI to any napping threads, since an HDEC interrupt * doesn't wake CPUs up from nap. @@ -2123,6 +2132,27 @@ _GLOBAL(kvmppc_h_cede) /* r3 = vcpu pointer, r11 = msr, r13 = paca */ /* save FP state */ bl kvmppc_save_fp + /* + * Set DEC to the smaller of DEC and HDEC, so that we wake + * no later than the end of our timeslice (HDEC interrupts + * don't wake us from nap). + */ + mfspr r3, SPRN_DEC + mfspr r4, SPRN_HDEC + mftb r5 + cmpw r3, r4 + ble 67f + mtspr SPRN_DEC, r4 +67: + /* save expiry time of guest decrementer */ + extsw r3, r3 + add r3, r3, r5 + ld r4, HSTATE_KVM_VCPU(r13) + ld r5, HSTATE_KVM_VCORE(r13) + ld r6, VCORE_TB_OFFSET(r5) + subf r3, r6, r3 /* convert to host TB value */ + std r3, VCPU_DEC_EXPIRES(r4) + #ifdef CONFIG_KVM_BOOK3S_HV_EXIT_TIMING ld r4, HSTATE_KVM_VCPU(r13) addi r3, r4, VCPU_TB_CEDE @@ -2180,6 +2210,15 @@ kvm_end_cede: /* load up FP state */ bl kvmppc_load_fp + /* Restore guest decrementer */ + ld r3, VCPU_DEC_EXPIRES(r4) + ld r5, HSTATE_KVM_VCORE(r13) + ld r6, VCORE_TB_OFFSET(r5) + add r3, r3, r6 /* convert host TB to guest TB value */ + mftb r7 + subf r3, r7, r3 + mtspr SPRN_DEC, r3 + /* Load NV GPRS */ ld r14, VCPU_GPR(R14)(r4) ld r15, VCPU_GPR(R15)(r4) -- 2.1.4
next prev parent reply other threads:[~2015-03-27 3:30 UTC|newest] Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-03-27 3:29 [PATCH 00/12] Remaining improvements for HV KVM Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras 2015-03-27 3:29 ` [PATCH 01/12] KVM: PPC: Book3S HV: Create debugfs file for each guest's HPT Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras 2015-03-27 3:29 ` [PATCH 02/12] KVM: PPC: Book3S HV: Accumulate timing information for real-mode code Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras 2015-03-27 11:47 ` Paul Mackerras 2015-03-27 11:47 ` Paul Mackerras 2015-03-27 3:29 ` [PATCH 03/12] KVM: PPC: Book3S HV: Simplify handling of VCPUs that need a VPA update Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras 2015-03-27 3:29 ` [PATCH 04/12] KVM: PPC: Book3S HV: Minor cleanups Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras 2015-03-27 3:29 ` [PATCH 05/12] KVM: PPC: Book3S HV: Move vcore preemption point up into kvmppc_run_vcpu Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras 2015-03-27 3:29 ` [PATCH 06/12] KVM: PPC: Book3S HV: Get rid of vcore nap_count and n_woken Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras 2015-03-27 3:29 ` [PATCH 07/12] KVM: PPC: Book3S HV: Don't wake thread with no vcpu on guest IPI Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras [this message] 2015-03-27 3:29 ` [PATCH 08/12] KVM: PPC: Book3S HV: Use decrementer to wake napping threads Paul Mackerras 2015-03-27 3:29 ` [PATCH 09/12] KVM: PPC: Book3S HV: Use bitmap of active threads rather than count Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras 2015-03-27 3:29 ` [PATCH 10/12] KVM: PPC: Book3S HV: Streamline guest entry and exit Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras 2015-03-27 3:29 ` [PATCH 11/12] KVM: PPC: Book3S HV: Translate kvmhv_commence_exit to C Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras 2015-03-27 3:29 ` [PATCH 12/12] KVM: PPC: Book3S HV: Use msgsnd for signalling threads on POWER8 Paul Mackerras 2015-03-27 3:29 ` Paul Mackerras 2015-03-28 3:21 [PATCH v2 00/12] Remaining improvements for HV KVM Paul Mackerras 2015-03-28 3:21 ` [PATCH 08/12] KVM: PPC: Book3S HV: Use decrementer to wake napping threads Paul Mackerras 2015-03-28 3:21 ` Paul Mackerras
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