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Mon, 18 Nov 2019 01:23:15 +0000 From: Michael Kelley To: Dexuan Cui , "linux-kernel@vger.kernel.org" , "tglx@linutronix.de" , "daniel.lezcano@linaro.org" , vkuznets , KY Srinivasan , Stephen Hemminger , "sashal@kernel.org" , "mingo@redhat.com" , "bp@alien8.de" , "hpa@zytor.com" , "x86@kernel.org" , "will@kernel.org" , "Ganapatrao.Kulkarni@cavium.com" , "james.morse@arm.com" , "steven.price@arm.com" , "josephl@nvidia.com" , "m.szyprowski@samsung.com" , "linux-hyperv@vger.kernel.org" Subject: RE: [PATCH v2 1/1] x86/hyperv: Initialize clockevents earlier in CPU onlining Thread-Topic: [PATCH v2 1/1] x86/hyperv: Initialize clockevents earlier in CPU onlining Thread-Index: AQHVmb9TAIfD7Ra2tkqgwSg/PXh9y6eLwmaQgARlu/A= Date: Mon, 18 Nov 2019 01:23:15 +0000 Message-ID: References: <1573607467-9456-1-git-send-email-mikelley@microsoft.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=True; 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x-microsoft-antispam-message-info: QbqfDrtmQ3I5+tJMGVMCYjFoiapROQEdVtjxYLSWA5hNunSF4dgf0ubvVdnRyRI6U+apUyjxdJQm9kFgE8BcCidb+FYxiMdpTtKhBz6OFdAQk+cV8JKAzW4ICQyIS9Pa44LB/59RBe91ToTMerONlj58sHlFCJTZP41Xq2P/TeJO+nNow2d1P1EqIaZfal2YkAOnY5Y3TyhZzBqEmNDPRImm+v7nWwTmH4HpS8oIbHRhI1Hg0JbUcJGYDmAIA68JXXQ9kJ+5rZNswpVtI1C3QSUQLHnig262t5xHvYiOXIEHB/01ZuYpxWg1lwO8iJed62bcduODuB8R09Yv9+vCi2Bk2MuOyVpZV4js/B0dr8fYYY6bHdwPl4mXQrgSX06UEHv8iUpFGmitwvcqNE6HO3Cn0S82kHoZnKqzUkCC8ZUkktcvnVIl5+oUbVcYz93+ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: c4d9dbeb-2bc0-4d0a-b8d0-08d76bc5e2e7 X-MS-Exchange-CrossTenant-originalarrivaltime: 18 Nov 2019 01:23:15.4751 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: o3uEdgvcvlCfYujrJOdiRmyozs1EUK6dcAe6pbe7qPtOYqYD26jgOBlZfrjgINDBYdvkvqJiXrRNEKYoJO698oHH/P/y0l1SnxWySgz6CLk= X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY4PR21MB0742 Sender: linux-hyperv-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org From: Dexuan Cui Sent: Thursday, November 14, 2019 1= 0:49 PM > > From: Michael Kelley > > Sent: Tuesday, November 12, 2019 5:12 PM > > ... > > @@ -190,14 +278,20 @@ void hv_stimer_free(void) > > void hv_stimer_global_cleanup(void) > > { > > int cpu; > > ... > > + /* > > + * hv_stime_legacy_cleanup() will stop the stimer if Direct > > + * Mode is not enabled, and fallback to the LAPIC timer. > > + */ > > + for_each_present_cpu(cpu) { > > + hv_stimer_legacy_cleanup(cpu); > > } > > + > > + /* > > + * If Direct Mode is enabled, the cpuhp teardown callback > > + * (hv_stimer_cleanup) will be run on all CPUs to stop the > > + * stimers. > > + */ > > hv_stimer_free(); > > } >=20 > In the case of direct_mode_enabled =3D=3D true: When hv_vmbus unloads, > vmbus_exit() -> hv_stimer_global_cleanup() -> hv_stimer_free() -> > cpuhp_remove_state() disables the direct mode timers. >=20 > This does not look symmetric since hv_stimer_alloc() is called before > hv_vmbus loads, but I suppose this is not a real issue because hv_vmbus > should never unload in practice. :-) Thanks for the review. Looking at this a bit more, ideally hv_stimer_global_cleanup() should go away entirely. vmbus_exit() should let the call to cpuhp_remove_state() clean up the stimer on each CPU via=20 hv_synic_cleanup(). But vmbus_exit() shuts down the VMbus first, which is really the wrong order. As you say, vmbus_exit() never gets called in practice, so it's not a current issue. But I'll look at fixing this in a future patch so that it makes logical sense. Michael >=20 > Tested-by: Dexuan Cui > Reviewed-by: Dexuan Cui