From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752671AbcGFFAk (ORCPT ); Wed, 6 Jul 2016 01:00:40 -0400 Received: from mx2.suse.de ([195.135.220.15]:49009 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750832AbcGFFAg (ORCPT ); Wed, 6 Jul 2016 01:00:36 -0400 From: Juergen Gross To: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Cc: sstabellini@kernel.org, boris.ostrovsky@oracle.com, david.vrabel@citrix.com, Juergen Gross Subject: [PATCH v2 3/3] xen: support runqueue steal time on xen Date: Wed, 6 Jul 2016 07:00:30 +0200 Message-Id: <1467781230-12484-4-git-send-email-jgross@suse.com> X-Mailer: git-send-email 2.6.6 In-Reply-To: <1467781230-12484-1-git-send-email-jgross@suse.com> References: <1467781230-12484-1-git-send-email-jgross@suse.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Up to now reading the stolen time of a remote cpu was not possible in a performant way under Xen. This made support of runqueue steal time via paravirt_steal_rq_enabled impossible. With the addition of an appropriate hypervisor interface this is now possible, so add the support. Signed-off-by: Juergen Gross --- V2: removed static variable as requested by Stefano Stabellini --- drivers/xen/time.c | 40 +++++++++++++++++++++++----------------- 1 file changed, 23 insertions(+), 17 deletions(-) diff --git a/drivers/xen/time.c b/drivers/xen/time.c index 2257b66..a7fe35b 100644 --- a/drivers/xen/time.c +++ b/drivers/xen/time.c @@ -47,27 +47,31 @@ static u64 get64(const u64 *p) return ret; } -/* - * Runstate accounting - */ -void xen_get_runstate_snapshot(struct vcpu_runstate_info *res) +static void xen_get_runstate_snapshot_cpu(struct vcpu_runstate_info *res, + unsigned int cpu) { u64 state_time; struct vcpu_runstate_info *state; BUG_ON(preemptible()); - state = this_cpu_ptr(&xen_runstate); + state = per_cpu_ptr(&xen_runstate, cpu); - /* - * The runstate info is always updated by the hypervisor on - * the current CPU, so there's no need to use anything - * stronger than a compiler barrier when fetching it. - */ do { state_time = get64(&state->state_entry_time); + rmb(); /* Hypervisor might update data. */ *res = READ_ONCE(*state); - } while (get64(&state->state_entry_time) != state_time); + rmb(); /* Hypervisor might update data. */ + } while (get64(&state->state_entry_time) != state_time || + (state_time & XEN_RUNSTATE_UPDATE)); +} + +/* + * Runstate accounting + */ +void xen_get_runstate_snapshot(struct vcpu_runstate_info *res) +{ + xen_get_runstate_snapshot_cpu(res, smp_processor_id()); } /* return true when a vcpu could run but has no real cpu to run on */ @@ -80,8 +84,7 @@ static u64 xen_steal_clock(int cpu) { struct vcpu_runstate_info state; - BUG_ON(cpu != smp_processor_id()); - xen_get_runstate_snapshot(&state); + xen_get_runstate_snapshot_cpu(&state, cpu); return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline]; } @@ -98,11 +101,14 @@ void xen_setup_runstate_info(int cpu) void __init xen_time_setup_guest(void) { + bool xen_runstate_remote; + + xen_runstate_remote = !HYPERVISOR_vm_assist(VMASST_CMD_enable, + VMASST_TYPE_runstate_update_flag); + pv_time_ops.steal_clock = xen_steal_clock; static_key_slow_inc(¶virt_steal_enabled); - /* - * We can't set paravirt_steal_rq_enabled as this would require the - * capability to read another cpu's runstate info. - */ + if (xen_runstate_remote) + static_key_slow_inc(¶virt_steal_rq_enabled); } -- 2.6.6