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Mon, 22 Mar 2021 18:04:33 -0700 (PDT) Received: from bobo.ibm.com ([58.84.78.96]) by smtp.gmail.com with ESMTPSA id e7sm14491894pfc.88.2021.03.22.18.04.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Mar 2021 18:04:33 -0700 (PDT) From: Nicholas Piggin To: kvm-ppc@vger.kernel.org Subject: [PATCH v4 25/46] KVM: PPC: Book3S HV P9: Use host timer accounting to avoid decrementer read Date: Tue, 23 Mar 2021 11:02:44 +1000 Message-Id: <20210323010305.1045293-26-npiggin@gmail.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20210323010305.1045293-1-npiggin@gmail.com> References: <20210323010305.1045293-1-npiggin@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" There is no need to save away the host DEC value, as it is derived from the host timer subsystem, which maintains the next timer time. Signed-off-by: Nicholas Piggin --- arch/powerpc/include/asm/time.h | 5 +++++ arch/powerpc/kernel/time.c | 1 + arch/powerpc/kvm/book3s_hv.c | 12 ++++++------ 3 files changed, 12 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/time.h index 68d94711811e..0128cd9769bc 100644 --- a/arch/powerpc/include/asm/time.h +++ b/arch/powerpc/include/asm/time.h @@ -101,6 +101,11 @@ extern void __init time_init(void); DECLARE_PER_CPU(u64, decrementers_next_tb); +static inline u64 timer_get_next_tb(void) +{ + return __this_cpu_read(decrementers_next_tb); +} + /* Convert timebase ticks to nanoseconds */ unsigned long long tb_to_ns(unsigned long long tb_ticks); diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index b67d93a609a2..c5d524622c17 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -108,6 +108,7 @@ struct clock_event_device decrementer_clockevent = { EXPORT_SYMBOL(decrementer_clockevent); DEFINE_PER_CPU(u64, decrementers_next_tb); +EXPORT_SYMBOL_GPL(decrementers_next_tb); static DEFINE_PER_CPU(struct clock_event_device, decrementers); #define XSEC_PER_SEC (1024*1024) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index bb30c5ab53d1..db807eebb3bd 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -3686,16 +3686,16 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long host_amr = mfspr(SPRN_AMR); unsigned long host_fscr = mfspr(SPRN_FSCR); s64 dec; - u64 tb; + u64 tb, next_timer; int trap, save_pmu; - dec = mfspr(SPRN_DEC); tb = mftb(); - if (dec < 0) + next_timer = timer_get_next_tb(); + if (tb >= next_timer) return BOOK3S_INTERRUPT_HV_DECREMENTER; - local_paca->kvm_hstate.dec_expires = dec + tb; - if (local_paca->kvm_hstate.dec_expires < time_limit) - time_limit = local_paca->kvm_hstate.dec_expires; + local_paca->kvm_hstate.dec_expires = next_timer; + if (next_timer < time_limit) + time_limit = next_timer; vcpu->arch.ceded = 0; -- 2.23.0