From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicholas Piggin Date: Tue, 23 Mar 2021 01:02:45 +0000 Subject: [PATCH v4 26/46] KVM: PPC: Book3S HV P9: Reduce mftb per guest entry/exit Message-Id: <20210323010305.1045293-27-npiggin@gmail.com> List-Id: References: <20210323010305.1045293-1-npiggin@gmail.com> In-Reply-To: <20210323010305.1045293-1-npiggin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kvm-ppc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org, Nicholas Piggin , Fabiano Rosas mftb is serialising (dispatch next-to-complete) so it is heavy weight for a mfspr. Avoid reading it multiple times in the entry or exit paths. A small number of cycles delay to timers is tolerable. Reviewed-by: Fabiano Rosas Signed-off-by: Nicholas Piggin --- arch/powerpc/kvm/book3s_hv.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index db807eebb3bd..1f38a0abc611 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -3540,12 +3540,13 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit, host_dawrx1 = mfspr(SPRN_DAWRX1); } - hdec = time_limit - mftb(); + tb = mftb(); + hdec = time_limit - tb; if (hdec < 0) return BOOK3S_INTERRUPT_HV_DECREMENTER; if (vc->tb_offset) { - u64 new_tb = mftb() + vc->tb_offset; + u64 new_tb = tb + vc->tb_offset; mtspr(SPRN_TBU40, new_tb); tb = mftb(); if ((tb & 0xffffff) < (new_tb & 0xffffff)) @@ -3744,7 +3745,7 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, if (!(vcpu->arch.ctrl & 1)) mtspr(SPRN_CTRLT, mfspr(SPRN_CTRLF) & ~1); - mtspr(SPRN_DEC, vcpu->arch.dec_expires - mftb()); + mtspr(SPRN_DEC, vcpu->arch.dec_expires - tb); if (kvmhv_on_pseries()) { /* @@ -3878,7 +3879,7 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, vc->entry_exit_map = 0x101; vc->in_guest = 0; - mtspr(SPRN_DEC, local_paca->kvm_hstate.dec_expires - mftb()); + mtspr(SPRN_DEC, local_paca->kvm_hstate.dec_expires - tb); mtspr(SPRN_SPRG_VDSO_WRITE, local_paca->sprg_vdso); kvmhv_load_host_pmu(); -- 2.23.0