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Tue, 14 Jul 2020 10:19:02 +0000 (UTC) Subject: Re: [RFC 1/3] x86: lpc9: let firmware negotiate CPU hotplug SMI feature To: Igor Mammedov , qemu-devel@nongnu.org References: <20200710161704.309824-1-imammedo@redhat.com> <20200710161704.309824-2-imammedo@redhat.com> From: Laszlo Ersek Message-ID: <470ed90d-6d2d-83b6-b9ce-c23e427ff2ba@redhat.com> Date: Tue, 14 Jul 2020 12:19:01 +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: <20200710161704.309824-2-imammedo@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 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=205.139.110.120; envelope-from=lersek@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/14 01:42:04 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 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_H2=-1, 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, liran.alon@oracle.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 07/10/20 18:17, Igor Mammedov wrote: > It will allow firmware to notify QEMU that firmware requires SMI > being triggered on CPU hotplug, so that it would be able to account > for hotplugged CPU and relocate it to new SMM base. > > Using the negotiated feature, 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 | 1 + > hw/i386/pc.c | 4 +++- > hw/isa/lpc_ich9.c | 7 +++++++ > 3 files changed, 11 insertions(+), 1 deletion(-) > > diff --git a/include/hw/i386/ich9.h b/include/hw/i386/ich9.h > index a98d10b252..422891a152 100644 > --- a/include/hw/i386/ich9.h > +++ b/include/hw/i386/ich9.h > @@ -247,5 +247,6 @@ 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 > > #endif /* HW_ICH9_H */ > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > index d7f27bc16b..6fe80c84d7 100644 > --- a/hw/i386/pc.c > +++ b/hw/i386/pc.c > @@ -97,7 +97,9 @@ > #include "fw_cfg.h" > #include "trace.h" > > -GlobalProperty pc_compat_5_0[] = {}; > +GlobalProperty pc_compat_5_0[] = { > + { "ICH9-LPC", "x-smi-cpu-hotplug", "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..83da7346ab 100644 > --- a/hw/isa/lpc_ich9.c > +++ b/hw/isa/lpc_ich9.c > @@ -373,6 +373,11 @@ 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)) { > + /* cpu hotplug 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 +752,8 @@ 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_END_OF_LIST(), > }; > > This patch looks good to me: Reviewed-by: Laszlo Ersek However I'd suggest that we introduce ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT at once (bit position 2). We don't have to handle it for real, but we should catch it in patch#2, and reject it gracefully. For that, the property would be called "x-smi-cpu-hot-unplug", and the error check in smi_features_ok_callback() would go like: 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))) { /* either one of the "CPU hotplug with SMI" and "CPU hot-unplug * with SMI" features requires SMI broadcast; leave @features_ok * at zero */ return; } The reason I'm suggesting catching LPC_SMI_F_CPU_HOT_UNPLUG_BIT at once is that people will inevitably try to un-plug, when they see plug succeed. The firmware itself does catch the (as yet unimplemented) un-plug attempt, but the way the firmware fails is not -- cannot be -- graceful. It hangs, intentionally. Failing the device_del QMP command is more graceful. (For this series, I'll provide test results once I've read the patches.) Thanks! Laszlo