From: "Huang, Kai" <kai.huang@intel.com>
To: "farman@linux.ibm.com" <farman@linux.ibm.com>,
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<linux-riscv@lists.infradead.org>
Subject: Re: [PATCH 38/44] KVM: Disable CPU hotplug during hardware enabling
Date: Thu, 10 Nov 2022 02:11:47 +0000 [thread overview]
Message-ID: <b198fe971cecd301f0c7c66028cfd71dd7ba7e62.camel@intel.com> (raw)
In-Reply-To: <88e920944de70e7d69a98f74005b49c59b5aaa3b.camel@intel.com>
On Thu, 2022-11-10 at 01:33 +0000, Huang, Kai wrote:
> > @@ -9283,7 +9283,13 @@ static int
> > kvm_x86_check_processor_compatibility(struct kvm_x86_init_ops *ops)
> > int cpu = smp_processor_id();
> > struct cpuinfo_x86 *c = &cpu_data(cpu);
> >
> > - WARN_ON(!irqs_disabled());
> > + /*
> > + * Compatibility checks are done when loading KVM and when enabling
> > + * hardware, e.g. during CPU hotplug, to ensure all online CPUs are
> > + * compatible, i.e. KVM should never perform a compatibility check
> > on
> > + * an offline CPU.
> > + */
> > + WARN_ON(!irqs_disabled() && cpu_active(cpu));
> >
>
> Also, the logic of:
>
> !irqs_disabled() && cpu_active(cpu)
>
> is quite weird.
>
> The original "WARN(!irqs_disabled())" is reasonable because in STARTING
> section
> the IRQ is indeed disabled.
>
> But this doesn't make sense anymore after we move to ONLINE section, in which
> IRQ has already been enabled (see start_secondary()). IIUC the WARN_ON()
> doesn't get exploded is purely because there's an additional cpu_active(cpu)
> check.
>
> So, a more reasonable check should be something like:
>
> WARN_ON(irqs_disabled() || cpu_active(cpu) || !cpu_online(cpu));
>
> Or we can simply do:
>
> WARN_ON(!cpu_online(cpu) || cpu_active(cpu));
>
> (because I don't know whether it's possible IRQ can somehow get disabled in
> ONLINE section).
>
> Btw above is purely based on code analysis, but I haven't done any test.
Hmm.. I wasn't thinking thoroughly. I forgot CPU compatibility check also
happens on all online cpus when loading KVM. For this case, IRQ is disabled and
cpu_active() is true. For the hotplug case, IRQ is enabled but cpu_active() is
false.
So WARN_ON(!irqs_disabled() && cpu_active(cpu)) looks reasonable. Sorry for the
noise. Just needed some time to connect the comment with the code.
next prev parent reply other threads:[~2022-11-10 2:12 UTC|newest]
Thread overview: 127+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-02 23:18 [PATCH 00/44] KVM: Rework kvm_init() and hardware enabling Sean Christopherson
2022-11-02 23:18 ` [PATCH 01/44] KVM: Register /dev/kvm as the _very_ last thing during initialization Sean Christopherson
2022-11-02 23:18 ` [PATCH 02/44] KVM: Initialize IRQ FD after arch hardware setup Sean Christopherson
2022-11-04 0:41 ` Chao Gao
2022-11-04 20:15 ` Sean Christopherson
2022-11-02 23:18 ` [PATCH 03/44] KVM: Allocate cpus_hardware_enabled " Sean Christopherson
2022-11-04 5:37 ` Yuan Yao
2022-11-02 23:18 ` [PATCH 04/44] KVM: Teardown VFIO ops earlier in kvm_exit() Sean Christopherson
2022-11-03 12:46 ` Cornelia Huck
2022-11-07 17:56 ` Eric Farman
2022-11-02 23:18 ` [PATCH 05/44] KVM: s390: Unwind kvm_arch_init() piece-by-piece() if a step fails Sean Christopherson
2022-11-07 17:57 ` Eric Farman
2022-11-02 23:18 ` [PATCH 06/44] KVM: s390: Move hardware setup/unsetup to init/exit Sean Christopherson
2022-11-07 17:58 ` Eric Farman
2022-11-02 23:18 ` [PATCH 07/44] KVM: x86: Do timer initialization after XCR0 configuration Sean Christopherson
2022-11-02 23:18 ` [PATCH 08/44] KVM: x86: Move hardware setup/unsetup to init/exit Sean Christopherson
2022-11-04 6:22 ` Yuan Yao
2022-11-04 16:31 ` Sean Christopherson
2022-11-02 23:18 ` [PATCH 09/44] KVM: Drop arch hardware (un)setup hooks Sean Christopherson
2022-11-07 3:01 ` Anup Patel
2022-11-07 18:22 ` Eric Farman
2022-11-02 23:18 ` [PATCH 10/44] KVM: VMX: Clean up eVMCS enabling if KVM initialization fails Sean Christopherson
2022-11-03 14:01 ` Paolo Bonzini
2022-11-03 14:04 ` Paolo Bonzini
2022-11-03 14:28 ` Vitaly Kuznetsov
2022-11-11 1:38 ` Sean Christopherson
2022-11-15 9:30 ` Vitaly Kuznetsov
2022-11-02 23:18 ` [PATCH 11/44] KVM: x86: Move guts of kvm_arch_init() to standalone helper Sean Christopherson
2022-11-02 23:18 ` [PATCH 12/44] KVM: VMX: Do _all_ initialization before exposing /dev/kvm to userspace Sean Christopherson
2022-11-02 23:18 ` [PATCH 13/44] KVM: x86: Serialize vendor module initialization (hardware setup) Sean Christopherson
2022-11-16 1:46 ` Huang, Kai
2022-11-16 15:52 ` Sean Christopherson
2022-11-02 23:18 ` [PATCH 14/44] KVM: arm64: Simplify the CPUHP logic Sean Christopherson
2022-11-02 23:18 ` [PATCH 15/44] KVM: arm64: Free hypervisor allocations if vector slot init fails Sean Christopherson
2022-11-02 23:18 ` [PATCH 16/44] KVM: arm64: Unregister perf callbacks if hypervisor finalization fails Sean Christopherson
2022-11-02 23:18 ` [PATCH 17/44] KVM: arm64: Do arm/arch initialiation without bouncing through kvm_init() Sean Christopherson
2022-11-03 7:25 ` Philippe Mathieu-Daudé
2022-11-03 15:29 ` Sean Christopherson
2022-11-02 23:18 ` [PATCH 18/44] KVM: arm64: Mark kvm_arm_init() and its unique descendants as __init Sean Christopherson
2022-11-02 23:18 ` [PATCH 19/44] KVM: MIPS: Hardcode callbacks to hardware virtualization extensions Sean Christopherson
2022-11-02 23:18 ` [PATCH 20/44] KVM: MIPS: Setup VZ emulation? directly from kvm_mips_init() Sean Christopherson
2022-11-03 7:10 ` Philippe Mathieu-Daudé
2022-11-02 23:18 ` [PATCH 21/44] KVM: MIPS: Register die notifier prior to kvm_init() Sean Christopherson
2022-11-03 7:12 ` Philippe Mathieu-Daudé
2022-11-02 23:18 ` [PATCH 22/44] KVM: RISC-V: Do arch init directly in riscv_kvm_init() Sean Christopherson
2022-11-03 7:14 ` Philippe Mathieu-Daudé
2022-11-07 3:05 ` Anup Patel
2022-11-02 23:18 ` [PATCH 23/44] KVM: RISC-V: Tag init functions and data with __init, __ro_after_init Sean Christopherson
2022-11-07 3:10 ` Anup Patel
2022-11-02 23:18 ` [PATCH 24/44] KVM: PPC: Move processor compatibility check to module init Sean Christopherson
2022-11-02 23:18 ` [PATCH 25/44] KVM: s390: Do s390 specific init without bouncing through kvm_init() Sean Christopherson
2022-11-03 7:16 ` Philippe Mathieu-Daudé
2022-11-03 12:44 ` Claudio Imbrenda
2022-11-03 13:21 ` Claudio Imbrenda
2022-11-07 18:22 ` Eric Farman
2022-11-02 23:18 ` [PATCH 26/44] KVM: s390: Mark __kvm_s390_init() and its descendants as __init Sean Christopherson
2022-11-07 18:22 ` Eric Farman
2022-11-02 23:18 ` [PATCH 27/44] KVM: Drop kvm_arch_{init,exit}() hooks Sean Christopherson
2022-11-03 7:18 ` Philippe Mathieu-Daudé
2022-11-07 3:13 ` Anup Patel
2022-11-07 19:08 ` Eric Farman
2022-11-02 23:18 ` [PATCH 28/44] KVM: VMX: Make VMCS configuration/capabilities structs read-only after init Sean Christopherson
2022-11-02 23:18 ` [PATCH 29/44] KVM: x86: Do CPU compatibility checks in x86 code Sean Christopherson
2022-11-02 23:18 ` [PATCH 30/44] KVM: Drop kvm_arch_check_processor_compat() hook Sean Christopherson
2022-11-03 7:20 ` Philippe Mathieu-Daudé
2022-11-07 3:16 ` Anup Patel
2022-11-07 19:08 ` Eric Farman
2022-11-02 23:18 ` [PATCH 31/44] KVM: x86: Use KBUILD_MODNAME to specify vendor module name Sean Christopherson
2022-11-02 23:18 ` [PATCH 32/44] KVM: x86: Unify pr_fmt to use module name for all KVM modules Sean Christopherson
2022-11-10 7:31 ` Robert Hoo
2022-11-10 16:50 ` Sean Christopherson
2022-11-30 23:02 ` Sean Christopherson
2022-12-01 1:34 ` Robert Hoo
2022-11-02 23:19 ` [PATCH 33/44] KVM: x86: Do VMX/SVM support checks directly in vendor code Sean Christopherson
2022-11-03 15:08 ` Paolo Bonzini
2022-11-03 18:35 ` Sean Christopherson
2022-11-03 18:46 ` Paolo Bonzini
2022-11-03 18:58 ` Sean Christopherson
2022-11-04 8:02 ` Paolo Bonzini
2022-11-04 15:40 ` Sean Christopherson
2022-11-15 22:50 ` Huang, Kai
2022-11-16 1:56 ` Sean Christopherson
2022-11-02 23:19 ` [PATCH 34/44] KVM: VMX: Shuffle support checks and hardware enabling code around Sean Christopherson
2022-11-02 23:19 ` [PATCH 35/44] KVM: SVM: Check for SVM support in CPU compatibility checks Sean Christopherson
2022-11-02 23:19 ` [PATCH 36/44] KVM: x86: Do compatibility checks when onlining CPU Sean Christopherson
2022-11-03 15:17 ` Paolo Bonzini
2022-11-03 17:44 ` Sean Christopherson
2022-11-03 17:57 ` Paolo Bonzini
2022-11-03 21:04 ` Isaku Yamahata
2022-11-03 22:34 ` Sean Christopherson
2022-11-04 7:18 ` Isaku Yamahata
2022-11-11 0:06 ` Sean Christopherson
2022-11-02 23:19 ` [PATCH 37/44] KVM: Rename and move CPUHP_AP_KVM_STARTING to ONLINE section Sean Christopherson
2022-11-10 7:26 ` Robert Hoo
2022-11-10 16:49 ` Sean Christopherson
2022-11-02 23:19 ` [PATCH 38/44] KVM: Disable CPU hotplug during hardware enabling Sean Christopherson
2022-11-10 1:08 ` Huang, Kai
2022-11-10 2:20 ` Huang, Kai
2022-11-10 1:33 ` Huang, Kai
2022-11-10 2:11 ` Huang, Kai [this message]
2022-11-10 16:58 ` Sean Christopherson
2022-11-15 20:16 ` Sean Christopherson
2022-11-15 20:21 ` Sean Christopherson
2022-11-16 12:23 ` Huang, Kai
2022-11-16 17:11 ` Sean Christopherson
2022-11-17 1:39 ` Huang, Kai
2022-11-17 15:16 ` Sean Christopherson
2022-11-02 23:19 ` [PATCH 39/44] KVM: Drop kvm_count_lock and instead protect kvm_usage_count with kvm_lock Sean Christopherson
2022-11-03 15:23 ` Paolo Bonzini
2022-11-03 17:53 ` Sean Christopherson
2022-11-02 23:19 ` [PATCH 40/44] KVM: Remove on_each_cpu(hardware_disable_nolock) in kvm_exit() Sean Christopherson
2022-11-02 23:19 ` [PATCH 41/44] KVM: Use a per-CPU variable to track which CPUs have enabled virtualization Sean Christopherson
2022-11-02 23:19 ` [PATCH 42/44] KVM: Make hardware_enable_failed a local variable in the "enable all" path Sean Christopherson
2022-11-02 23:19 ` [PATCH 43/44] KVM: Register syscore (suspend/resume) ops early in kvm_init() Sean Christopherson
2022-11-02 23:19 ` [PATCH 44/44] KVM: Opt out of generic hardware enabling on s390 and PPC Sean Christopherson
2022-11-07 3:23 ` Anup Patel
2022-11-03 12:08 ` [PATCH 00/44] KVM: Rework kvm_init() and hardware enabling Christian Borntraeger
2022-11-03 15:27 ` Paolo Bonzini
2022-11-04 7:17 ` Isaku Yamahata
2022-11-04 7:59 ` Paolo Bonzini
2022-11-04 20:27 ` Sean Christopherson
2022-11-07 21:46 ` Isaku Yamahata
2022-11-08 1:09 ` Huang, Kai
2022-11-08 5:43 ` Isaku Yamahata
2022-11-08 8:56 ` Huang, Kai
2022-11-08 10:35 ` Huang, Kai
2022-11-08 17:46 ` Sean Christopherson
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