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From: Thomas Gleixner <tglx@linutronix.de>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Kuppuswamy Sathyanarayanan
	<sathyanarayanan.kuppuswamy@linux.intel.com>,
	Elena Reshetova <elena.reshetova@intel.com>,
	Jun Nakajima <jun.nakajima@intel.com>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	kexec@lists.infradead.org, linux-coco@lists.linux.dev,
	linux-kernel@vger.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH 02/13] kernel/cpu: Add support for declaring CPU hotplug not supported
Date: Wed, 11 Oct 2023 15:08:11 +0200	[thread overview]
Message-ID: <87il7dl32c.ffs@tglx> (raw)
In-Reply-To: <20231005131402.14611-3-kirill.shutemov@linux.intel.com>

On Thu, Oct 05 2023 at 16:13, Kirill A. Shutemov wrote:
> The function cpu_hotplug_not_supported() can be called to indicate that
> CPU hotplug should be disabled. It does not prevent the initial bring up
> of the CPU, but it stops subsequent offlining.

This tells me what the patch is doing, but not the why.

> This function is intended to replace CC_ATTR_HOTPLUG_DISABLED.

> --- a/include/linux/cpu.h
> +++ b/include/linux/cpu.h
> @@ -132,6 +132,7 @@ extern void cpus_read_lock(void);
>  extern void cpus_read_unlock(void);
>  extern int  cpus_read_trylock(void);
>  extern void lockdep_assert_cpus_held(void);
> +extern void cpu_hotplug_not_supported(void);

This function name sucks.

The point is as you explained to prevent offlining, but not onlining. So
can we please make this very clear? Something like:

    cpu_hotplug_disable_offlining()

> +/* Cleared if platform declares CPU hotplug not supported */
> +static bool cpu_hotplug_supported = true;

Again. This is not about disabling hotplug all together. Something like:

static bool cpu_hotplug_offline_disabled;

Which expresses clearly what this is about and does not require this
awkward negation.

Thanks,

        tglx

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec

WARNING: multiple messages have this Message-ID (diff)
From: Thomas Gleixner <tglx@linutronix.de>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Kuppuswamy Sathyanarayanan
	<sathyanarayanan.kuppuswamy@linux.intel.com>,
	Elena Reshetova <elena.reshetova@intel.com>,
	Jun Nakajima <jun.nakajima@intel.com>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	kexec@lists.infradead.org, linux-coco@lists.linux.dev,
	linux-kernel@vger.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH 02/13] kernel/cpu: Add support for declaring CPU hotplug not supported
Date: Wed, 11 Oct 2023 15:08:11 +0200	[thread overview]
Message-ID: <87il7dl32c.ffs@tglx> (raw)
In-Reply-To: <20231005131402.14611-3-kirill.shutemov@linux.intel.com>

On Thu, Oct 05 2023 at 16:13, Kirill A. Shutemov wrote:
> The function cpu_hotplug_not_supported() can be called to indicate that
> CPU hotplug should be disabled. It does not prevent the initial bring up
> of the CPU, but it stops subsequent offlining.

This tells me what the patch is doing, but not the why.

> This function is intended to replace CC_ATTR_HOTPLUG_DISABLED.

> --- a/include/linux/cpu.h
> +++ b/include/linux/cpu.h
> @@ -132,6 +132,7 @@ extern void cpus_read_lock(void);
>  extern void cpus_read_unlock(void);
>  extern int  cpus_read_trylock(void);
>  extern void lockdep_assert_cpus_held(void);
> +extern void cpu_hotplug_not_supported(void);

This function name sucks.

The point is as you explained to prevent offlining, but not onlining. So
can we please make this very clear? Something like:

    cpu_hotplug_disable_offlining()

> +/* Cleared if platform declares CPU hotplug not supported */
> +static bool cpu_hotplug_supported = true;

Again. This is not about disabling hotplug all together. Something like:

static bool cpu_hotplug_offline_disabled;

Which expresses clearly what this is about and does not require this
awkward negation.

Thanks,

        tglx

  parent reply	other threads:[~2023-10-11 13:08 UTC|newest]

Thread overview: 106+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-05 13:13 [PATCH 00/13] x86/tdx: Add kexec support Kirill A. Shutemov
2023-10-05 13:13 ` Kirill A. Shutemov
2023-10-05 13:13 ` [PATCH 01/13] x86/acpi: Extract ACPI MADT wakeup code into a separate file Kirill A. Shutemov
2023-10-05 13:13   ` Kirill A. Shutemov
2023-10-06 10:22   ` Huang, Kai
2023-10-06 10:22     ` Huang, Kai
2023-10-06 11:59     ` kirill.shutemov
2023-10-06 11:59       ` kirill.shutemov
2023-10-06 18:33   ` Kuppuswamy Sathyanarayanan
2023-10-06 18:33     ` Kuppuswamy Sathyanarayanan
2023-10-09 13:32     ` Kirill A. Shutemov
2023-10-09 13:32       ` Kirill A. Shutemov
2023-10-05 13:13 ` [PATCH 02/13] kernel/cpu: Add support for declaring CPU hotplug not supported Kirill A. Shutemov
2023-10-10 13:35   ` Kuppuswamy Sathyanarayanan
2023-10-10 13:35     ` Kuppuswamy Sathyanarayanan
2023-10-11 13:07     ` Kirill A. Shutemov
2023-10-11 13:07       ` Kirill A. Shutemov
2023-10-11 13:08   ` Thomas Gleixner [this message]
2023-10-11 13:08     ` Thomas Gleixner
2023-10-05 13:13 ` [PATCH 03/13] cpu/hotplug, x86/acpi: Disable CPU hotplug for ACPI MADT wakeup Kirill A. Shutemov
2023-10-05 13:13   ` Kirill A. Shutemov
2023-10-10 10:24   ` Huang, Kai
2023-10-10 10:24     ` Huang, Kai
2023-10-20 11:58     ` Huang, Kai
2023-10-20 11:58       ` Huang, Kai
2023-10-20 12:42       ` kirill.shutemov
2023-10-20 12:42         ` kirill.shutemov
2023-10-10 13:39   ` Kuppuswamy Sathyanarayanan
2023-10-10 13:39     ` Kuppuswamy Sathyanarayanan
2023-10-11 13:09   ` Thomas Gleixner
2023-10-11 13:09     ` Thomas Gleixner
2023-10-05 13:13 ` [PATCH 04/13] x86/kvm: Do not try to disable kvmclock if it was not enabled Kirill A. Shutemov
2023-10-05 13:13   ` Kirill A. Shutemov
2023-10-06 14:36   ` Sean Christopherson
2023-10-06 14:36     ` Sean Christopherson
2023-10-06 14:50     ` Kirill A. Shutemov
2023-10-06 14:50       ` Kirill A. Shutemov
2023-10-10 13:53   ` Kuppuswamy Sathyanarayanan
2023-10-10 13:53     ` Kuppuswamy Sathyanarayanan
2023-10-11 13:11     ` Kirill A. Shutemov
2023-10-11 13:11       ` Kirill A. Shutemov
2023-10-05 13:13 ` [PATCH 05/13] x86/kexec: Keep CR4.MCE set during kexec for TDX guest Kirill A. Shutemov
2023-10-05 13:13   ` Kirill A. Shutemov
2023-10-09 12:30   ` Huang, Kai
2023-10-09 12:30     ` Huang, Kai
2023-10-09 13:32     ` kirill.shutemov
2023-10-09 13:32       ` kirill.shutemov
2023-10-05 13:13 ` [PATCH 06/13] x86/mm: Make x86_platform.guest.enc_status_change_*() return errno Kirill A. Shutemov
2023-10-05 13:13 ` [PATCH 07/13] x86/mm: Return correct level from lookup_address() if pte is none Kirill A. Shutemov
2023-10-05 13:13   ` Kirill A. Shutemov
2023-10-05 13:13 ` [PATCH 08/13] KVM: x86: Add config option to gate emergency virt callback support Kirill A. Shutemov
2023-10-05 13:13   ` Kirill A. Shutemov
2023-10-05 13:13 ` [PATCH 09/13] x86/tdx: Account shared memory Kirill A. Shutemov
2023-10-05 13:13   ` Kirill A. Shutemov
2023-10-10 10:05   ` Huang, Kai
2023-10-10 10:05     ` Huang, Kai
2023-10-11 13:14     ` kirill.shutemov
2023-10-11 13:14       ` kirill.shutemov
2023-10-05 13:13 ` [PATCH 10/13] x86/tdx: Convert shared memory back to private on kexec Kirill A. Shutemov
2023-10-05 18:41   ` Kalra, Ashish
2023-10-05 18:41     ` Kalra, Ashish
2023-10-05 21:28     ` Kirill A. Shutemov
2023-10-05 21:28       ` Kirill A. Shutemov
2023-10-05 22:01       ` Kalra, Ashish
2023-10-05 22:01         ` Kalra, Ashish
2023-10-05 22:28         ` Kirill A. Shutemov
2023-10-05 22:28           ` Kirill A. Shutemov
2023-10-06 19:24           ` Kalra, Ashish
2023-10-06 19:24             ` Kalra, Ashish
2023-10-20  9:21             ` Kirill A. Shutemov
2023-10-20  9:21               ` Kirill A. Shutemov
2023-10-20  9:39               ` Kirill A. Shutemov
2023-10-20  9:39                 ` Kirill A. Shutemov
2023-10-06 14:58   ` Sean Christopherson
2023-10-06 14:58     ` Sean Christopherson
2023-10-06 15:11     ` Kirill A. Shutemov
2023-10-06 15:11       ` Kirill A. Shutemov
2023-10-06 22:15       ` Kalra, Ashish
2023-10-06 22:15         ` Kalra, Ashish
2023-10-08  8:35   ` Baoquan He
2023-10-08  8:35     ` Baoquan He
2023-10-09 13:35     ` Kirill A. Shutemov
2023-10-09 13:35       ` Kirill A. Shutemov
2023-10-05 13:14 ` [PATCH 11/13] x86/mm: Make e820_end_ram_pfn() cover E820_TYPE_ACPI ranges Kirill A. Shutemov
2023-10-05 13:14   ` Kirill A. Shutemov
2023-10-05 13:14 ` [PATCH 12/13] x86/acpi: Do not attempt to bring up secondary CPUs in kexec case Kirill A. Shutemov
2023-10-05 13:14   ` Kirill A. Shutemov
2023-10-20  3:29   ` Huang, Kai
2023-10-20  3:29     ` Huang, Kai
2023-10-20  9:29     ` kirill.shutemov
2023-10-20  9:29       ` kirill.shutemov
2023-10-05 13:14 ` [PATCH 13/13] x86/acpi: Add support for CPU offlining for ACPI MADT wakeup method Kirill A. Shutemov
2023-10-20  9:49   ` Huang, Kai
2023-10-20  9:49     ` Huang, Kai
2023-10-20 10:42     ` kirill.shutemov
2023-10-20 10:42       ` kirill.shutemov
2023-10-20 11:21   ` Huang, Kai
2023-10-20 11:21     ` Huang, Kai
2023-10-20 12:34     ` kirill.shutemov
2023-10-20 12:34       ` kirill.shutemov
2023-10-08 23:49 ` [PATCH 00/13] x86/tdx: Add kexec support Baoquan He
2023-10-08 23:49   ` Baoquan He
2023-10-09 13:36   ` Kirill A. Shutemov
2023-10-09 13:36     ` Kirill A. Shutemov
2023-10-09 14:13     ` Baoquan He
2023-10-09 14:13       ` Baoquan He

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