From: Nicholas Piggin <npiggin@gmail.com>
To: kvm-ppc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail.com>,
Fabiano Rosas <farosas@linux.ibm.com>
Subject: [PATCH v3 06/52] KVM: PPC: Book3S HV P9: Reduce mftb per guest entry/exit
Date: Tue, 5 Oct 2021 02:00:03 +1000 [thread overview]
Message-ID: <20211004160049.1338837-7-npiggin@gmail.com> (raw)
In-Reply-To: <20211004160049.1338837-1-npiggin@gmail.com>
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 <farosas@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
arch/powerpc/kvm/book3s_hv.c | 4 ++--
arch/powerpc/kvm/book3s_hv_p9_entry.c | 5 +++--
2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 30d400bf161b..e4482bf546ed 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -3927,7 +3927,7 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
*
* XXX: Another day's problem.
*/
- mtspr(SPRN_DEC, vcpu->arch.dec_expires - mftb());
+ mtspr(SPRN_DEC, vcpu->arch.dec_expires - tb);
if (kvmhv_on_pseries()) {
/*
@@ -4050,7 +4050,7 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
vc->in_guest = 0;
next_timer = timer_get_next_tb();
- set_dec(next_timer - mftb());
+ set_dec(next_timer - tb);
/* We may have raced with new irq work */
if (test_irq_work_pending())
set_dec(1);
diff --git a/arch/powerpc/kvm/book3s_hv_p9_entry.c b/arch/powerpc/kvm/book3s_hv_p9_entry.c
index 0ff9ddb5e7ca..bd8cf0a65ce8 100644
--- a/arch/powerpc/kvm/book3s_hv_p9_entry.c
+++ b/arch/powerpc/kvm/book3s_hv_p9_entry.c
@@ -203,7 +203,8 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
unsigned long host_dawr1;
unsigned long host_dawrx1;
- hdec = time_limit - mftb();
+ tb = mftb();
+ hdec = time_limit - tb;
if (hdec < 0)
return BOOK3S_INTERRUPT_HV_DECREMENTER;
@@ -215,7 +216,7 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc
vcpu->arch.ceded = 0;
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))
--
2.23.0
next prev parent reply other threads:[~2021-10-04 16:05 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-04 15:59 [PATCH v3 00/52] KVM: PPC: Book3S HV P9: entry/exit optimisations Nicholas Piggin
2021-10-04 15:59 ` [PATCH v3 01/52] powerpc/64s: Remove WORT SPR from POWER9/10 (take 2) Nicholas Piggin
2021-10-04 15:59 ` [PATCH v3 02/52] powerpc/64s: guard optional TIDR SPR with CPU ftr test Nicholas Piggin
2021-10-11 18:44 ` Fabiano Rosas
2021-10-12 2:08 ` Michael Ellerman
2021-10-13 16:51 ` Fabiano Rosas
2021-10-04 16:00 ` [PATCH v3 03/52] KMV: PPC: Book3S HV P9: Use set_dec to set decrementer to host Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 04/52] KVM: PPC: Book3S HV P9: Use host timer accounting to avoid decrementer read Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 05/52] KVM: PPC: Book3S HV P9: Use large decrementer for HDEC Nicholas Piggin
2021-10-04 16:00 ` Nicholas Piggin [this message]
2021-10-04 16:00 ` [PATCH v3 07/52] powerpc/time: add API for KVM to re-arm the host timer/decrementer Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 08/52] KVM: PPC: Book3S HV: POWER10 enable HAIL when running radix guests Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 09/52] powerpc/64s: Keep AMOR SPR a constant ~0 at runtime Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 10/52] KVM: PPC: Book3S HV: Don't always save PMU for guest capable of nesting Nicholas Piggin
2021-10-16 12:38 ` Fabiano Rosas
2021-10-20 5:26 ` Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 11/52] powerpc/64s: Always set PMU control registers to frozen/disabled when not in use Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 12/52] powerpc/64s: Implement PMU override command line option Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 13/52] KVM: PPC: Book3S HV P9: Implement PMU save/restore in C Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 14/52] KVM: PPC: Book3S HV P9: Factor PMU save/load into context switch functions Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 15/52] KVM: PPC: Book3S HV P9: Demand fault PMU SPRs when marked not inuse Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 16/52] KVM: PPC: Book3S HV P9: Factor out yield_count increment Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 17/52] KVM: PPC: Book3S HV: CTRL SPR does not require read-modify-write Nicholas Piggin
2021-10-16 12:54 ` Fabiano Rosas
2021-10-04 16:00 ` [PATCH v3 18/52] KVM: PPC: Book3S HV P9: Move SPRG restore to restore_p9_host_os_sprs Nicholas Piggin
2021-10-16 12:59 ` Fabiano Rosas
2021-10-04 16:00 ` [PATCH v3 19/52] KVM: PPC: Book3S HV P9: Reduce mtmsrd instructions required to save host SPRs Nicholas Piggin
2021-10-16 13:45 ` Fabiano Rosas
2021-10-20 5:35 ` Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 20/52] KVM: PPC: Book3S HV P9: Improve mtmsrd scheduling by delaying MSR[EE] disable Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 21/52] KVM: PPC: Book3S HV P9: Add kvmppc_stop_thread to match kvmppc_start_thread Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 22/52] KVM: PPC: Book3S HV: Change dec_expires to be relative to guest timebase Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 23/52] KVM: PPC: Book3S HV P9: Move TB updates Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 24/52] KVM: PPC: Book3S HV P9: Optimise timebase reads Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 25/52] KVM: PPC: Book3S HV P9: Avoid SPR scoreboard stalls Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 26/52] KVM: PPC: Book3S HV P9: Only execute mtSPR if the value changed Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 27/52] KVM: PPC: Book3S HV P9: Juggle SPR switching around Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 28/52] KVM: PPC: Book3S HV P9: Move vcpu register save/restore into functions Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 29/52] KVM: PPC: Book3S HV P9: Move host OS save/restore functions to built-in Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 30/52] KVM: PPC: Book3S HV P9: Move nested guest entry into its own function Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 31/52] KVM: PPC: Book3S HV P9: Move remaining SPR and MSR access into low level entry Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 32/52] KVM: PPC: Book3S HV P9: Implement TM fastpath for guest entry/exit Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 33/52] KVM: PPC: Book3S HV P9: Switch PMU to guest as late as possible Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 34/52] KVM: PPC: Book3S HV P9: Restrict DSISR canary workaround to processors that require it Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 35/52] KVM: PPC: Book3S HV P9: More SPR speed improvements Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 36/52] KVM: PPC: Book3S HV P9: Demand fault EBB facility registers Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 37/52] KVM: PPC: Book3S HV P9: Demand fault TM " Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 38/52] KVM: PPC: Book3S HV P9: Use Linux SPR save/restore to manage some host SPRs Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 39/52] KVM: PPC: Book3S HV P9: Comment and fix MMU context switching code Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 40/52] KVM: PPC: Book3S HV P9: Test dawr_enabled() before saving host DAWR SPRs Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 41/52] KVM: PPC: Book3S HV P9: Don't restore PSSCR if not needed Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 42/52] KVM: PPC: Book3S HV P9: Avoid tlbsync sequence on radix guest exit Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 43/52] KVM: PPC: Book3S HV Nested: Avoid extra mftb() in nested entry Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 44/52] KVM: PPC: Book3S HV P9: Improve mfmsr performance on entry Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 45/52] KVM: PPC: Book3S HV P9: Optimise hash guest SLB saving Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 46/52] KVM: PPC: Book3S HV P9: Avoid changing MSR[RI] in entry and exit Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 47/52] KVM: PPC: Book3S HV P9: Add unlikely annotation for !mmu_ready Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 48/52] KVM: PPC: Book3S HV P9: Avoid cpu_in_guest atomics on entry and exit Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 49/52] KVM: PPC: Book3S HV P9: Remove most of the vcore logic Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 50/52] KVM: PPC: Book3S HV P9: Tidy kvmppc_create_dtl_entry Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 51/52] KVM: PPC: Book3S HV P9: Stop using vc->dpdes Nicholas Piggin
2021-10-04 16:00 ` [PATCH v3 52/52] KVM: PPC: Book3S HV P9: Remove subcore HMI handling Nicholas Piggin
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