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Wed, 22 Jul 2020 12:03:18 +0000 (UTC) Subject: Re: [PATCH 1/6] x86: lpc9: let firmware negotiate 'CPU hotplug with SMI' features To: Igor Mammedov , qemu-devel@nongnu.org References: <20200720141610.574308-1-imammedo@redhat.com> <20200720141610.574308-2-imammedo@redhat.com> From: Laszlo Ersek Message-ID: <00b7e32c-36ad-a71a-00da-d1f0d9977e79@redhat.com> Date: Wed, 22 Jul 2020 14:03:17 +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: <20200720141610.574308-2-imammedo@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 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=207.211.31.81; envelope-from=lersek@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/21 23:34:34 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_H3=-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: > It will allow firmware to notify QEMU that firmware requires SMI > being triggered on CPU hot[un]plug, so that it would be able to account > for hotplugged CPU and relocate it to new SMM base and/or safely remove > CPU on unplug. > > Using negotiated features, follow up patches will insert SMI upcall > into AML code, to make sure that firmware processes hotplug before > guest OS would attempt to use new CPU. > > Signed-off-by: Igor Mammedov > --- > include/hw/i386/ich9.h | 2 ++ > hw/i386/pc.c | 5 ++++- > hw/isa/lpc_ich9.c | 12 ++++++++++++ > 3 files changed, 18 insertions(+), 1 deletion(-) > > diff --git a/include/hw/i386/ich9.h b/include/hw/i386/ich9.h > index a98d10b252..d1bb3f7bf0 100644 > --- a/include/hw/i386/ich9.h > +++ b/include/hw/i386/ich9.h > @@ -247,5 +247,7 @@ typedef struct ICH9LPCState { > > /* bit positions used in fw_cfg SMI feature negotiation */ > #define ICH9_LPC_SMI_F_BROADCAST_BIT 0 > +#define ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT 1 > +#define ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT 2 > > #endif /* HW_ICH9_H */ > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > index 3d419d5991..57d50fad6b 100644 > --- a/hw/i386/pc.c > +++ b/hw/i386/pc.c > @@ -97,7 +97,10 @@ > #include "fw_cfg.h" > #include "trace.h" > > -GlobalProperty pc_compat_5_0[] = {}; > +GlobalProperty pc_compat_5_0[] = { > + { "ICH9-LPC", "x-smi-cpu-hotplug", "off" }, > + { "ICH9-LPC", "x-smi-cpu-hotunplug", "off" }, > +}; > const size_t pc_compat_5_0_len = G_N_ELEMENTS(pc_compat_5_0); > > GlobalProperty pc_compat_4_2[] = { > diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c > index cd6e169d47..c9305080b5 100644 > --- a/hw/isa/lpc_ich9.c > +++ b/hw/isa/lpc_ich9.c > @@ -373,6 +373,14 @@ static void smi_features_ok_callback(void *opaque) > /* guest requests invalid features, leave @features_ok at zero */ > return; > } > + if (!(guest_features & BIT_ULL(ICH9_LPC_SMI_F_BROADCAST_BIT)) && > + guest_features & (BIT_ULL(ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT) | > + BIT_ULL(ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT))) { > + /* cpu hot-[un]plug with SMI requires SMI broadcast, > + * leave @features_ok at zero > + */ > + return; > + } > > /* valid feature subset requested, lock it down, report success */ > lpc->smi_negotiated_features = guest_features; > @@ -747,6 +755,10 @@ static Property ich9_lpc_properties[] = { > DEFINE_PROP_BOOL("noreboot", ICH9LPCState, pin_strap.spkr_hi, true), > DEFINE_PROP_BIT64("x-smi-broadcast", ICH9LPCState, smi_host_features, > ICH9_LPC_SMI_F_BROADCAST_BIT, true), > + DEFINE_PROP_BIT64("x-smi-cpu-hotplug", ICH9LPCState, smi_host_features, > + ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT, true), > + DEFINE_PROP_BIT64("x-smi-cpu-hotunplug", ICH9LPCState, smi_host_features, > + ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT, true), > DEFINE_PROP_END_OF_LIST(), > }; > > (1) I think that, at this time, the default value for "x-smi-cpu-hotunplug" should be false. Accordingly, the "x-smi-cpu-hotunplug" compat property should be dropped. The reason is that in this series, QEMU won't actually learn to handle CPU hot-unplug with SMI. We shouldn't advertize support for it. We should only recognize the feature, so that the QMP command can rely on it for rejecting hot-unplug attempts. If (later) we have a more advanced OVMF binary with unplug support (so that OVMF would try to negotiate unplug), but the user runs it on QEMU-5.1 (or more precisely with an 5.1 machine type), which will support plug, but not unplug, then QEMU should reject the device_del QMP command. In brief, we need both properties because we want both device_add and device_del to fail gracefully, but the default values (and accordingly the compat properties) should reflect the actual feature support. So unplug should default to false at this point. Thanks, Laszlo