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Wed, 22 Jul 2020 13:24:21 +0000 (UTC) Subject: Re: [PATCH 3/6] x86: cpuhp: refuse cpu hot-unplug request earlier if not supported To: Igor Mammedov , qemu-devel@nongnu.org References: <20200720141610.574308-1-imammedo@redhat.com> <20200720141610.574308-4-imammedo@redhat.com> From: Laszlo Ersek Message-ID: <5e6b9302-d847-1423-35fe-2076263ccd61@redhat.com> Date: Wed, 22 Jul 2020 15:24:21 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200720141610.574308-4-imammedo@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.120; envelope-from=lersek@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/22 00:40:35 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: boris.ostrovsky@oracle.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 07/20/20 16:16, Igor Mammedov wrote: > CPU hot-unplug with SMM requires firmware participation to prevent > guest crash (i.e. CPU can be removed only after OS _and_ firmware > were prepared for th action). (1) s/th action/the action/ > Previous patches introduced ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT > feature bit, which is advertised by firmware when it has support > for CPU hot-unplug. Use it to check if guest is able to handle > unplug and make device_del fail gracefully if hot-unplug feature > hasn't been negotiated. > > Signed-off-by: Igor Mammedov > --- > hw/acpi/ich9.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/hw/acpi/ich9.c b/hw/acpi/ich9.c > index 0acc9a3107..98fc363186 100644 > --- a/hw/acpi/ich9.c > +++ b/hw/acpi/ich9.c > @@ -460,6 +460,17 @@ void ich9_pm_device_unplug_request_cb(HotplugHandler *hotplug_dev, > errp); > } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU) && > !lpc->pm.cpu_hotplug_legacy) { > + uint64_t negotiated = lpc->smi_negotiated_features; > + > + if (negotiated & BIT_ULL(ICH9_LPC_SMI_F_BROADCAST_BIT) && > + !(negotiated & BIT_ULL(ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT))) { > + error_setg(errp, "cpu hot-unplug with SMI wasn't enabled " > + "by firmware"); > + error_append_hint(errp, "update machine type to newer than 5.1 " > + "and firmware that suppors CPU hot-unplug with SMM"); (2) I think the "machine type to newer than 5.1" reference should be removed at this point. (Similarly to how "x-smi-cpu-hotunplug" should default to "false" at this point in time, in patch#1.) We don't know when hot-unplug will work; we only know that it doesn't work now. We could say something like error_append_hint(errp, "update machine type to a version having " "x-smi-cpu-hotunplug=on and firmware that " "suppors CPU hot-unplug with SMM"); > + return; > + } > + > acpi_cpu_unplug_request_cb(hotplug_dev, &lpc->pm.cpuhp_state, > dev, errp); > } else { > These superficial comments aside, the patch works for me: Tested-by: Laszlo Ersek and with (1) and (2) fixed: Reviewed-by: Laszlo Ersek Thanks Laszlo