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From: "Li, Aubrey" <aubrey.li@linux.intel.com>
To: Thomas Gleixner <tglx@linutronix.de>, Aubrey Li <aubrey.intel@gmail.com>
Cc: Daniel Drake <drake@endlessm.com>,
	x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
	"H . Peter Anvin" <hpa@zytor.com>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	Endless Linux Upstreaming Team <linux@endlessm.com>
Subject: Re: setup_boot_APIC_clock() NULL dereference during early boot on reduced hardware platforms
Date: Thu, 1 Aug 2019 16:21:31 +0800	[thread overview]
Message-ID: <81666b28-d029-56c3-8978-90abc219d1b7@linux.intel.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1908011011250.1788@nanos.tec.linutronix.de>

On 2019/8/1 16:13, Thomas Gleixner wrote:
> On Thu, 1 Aug 2019, Aubrey Li wrote:
>> On Thu, Aug 1, 2019 at 3:35 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>>>
>>> On Thu, 1 Aug 2019, Aubrey Li wrote:
>>>> On Thu, Aug 1, 2019 at 2:26 PM Daniel Drake <drake@endlessm.com> wrote:
>>>>> global_clock_event is NULL here. This is a "reduced hardware" ACPI
>>>>> platform so acpi_generic_reduced_hw_init() has set timer_init to NULL,
>>>>> avoiding the usual codepaths that would set up global_clock_event.
>>>>>
>>>> IIRC, acpi_generic_reduced_hw_init() avoids initializing PIT, the status of
>>>> this legacy device is unknown in ACPI hw-reduced mode.
>>>>
>>>>> I tried the obvious:
>>>>>  if (!global_clock_event)
>>>>>     return -1;
>>>>>
>>>> No, the platform needs a global clock event, can you turn on some other
>>>
>>> Wrong. The kernel boots perfectly fine without a global clock event. But
>>> for that the TSC and LAPIC frequency must be known.
>>
>> I think LAPIC fast calibrate is only supported on intel platform, while
>> Daniel's box is an AMD platform. That's why lapic_init_clockevent() failed
>> and fall into the code path which needs a global clock event.
> 
> We know that.
> 
> The point is that it does not matter which vendor a CPU comes from. The
> kernel does support legacyless boot when the frequencies are known. Whether
> that's currently possible on that particular CPU is a different question.
> 
Yeah, I should specify, Daniel, your platform needs a global clock event, ;-)

Thanks,
-Aubrey

  reply	other threads:[~2019-08-01  8:21 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-01  6:24 Daniel Drake
2019-08-01  7:16 ` Aubrey Li
2019-08-01  7:35   ` Thomas Gleixner
2019-08-01  7:56     ` Aubrey Li
2019-08-01  8:13       ` Thomas Gleixner
2019-08-01  8:21         ` Li, Aubrey [this message]
2019-08-01 10:13           ` Thomas Gleixner
2019-08-01 15:44             ` Lendacky, Thomas
2019-08-08 20:36               ` Thomas Gleixner
2019-08-08 21:01                 ` Lendacky, Thomas
2019-08-08 21:08                   ` Thomas Gleixner
2019-08-08 21:36                     ` Lendacky, Thomas
2019-08-09 12:54                       ` [PATCH] x86/apic: Handle missing global clockevent gracefully Thomas Gleixner
2019-08-09 12:59                         ` Jiri Slaby
2019-08-09 13:58                         ` Lendacky, Thomas
2019-08-09 19:40                           ` Thomas Gleixner
2019-08-12  6:16                         ` Daniel Drake
2019-08-12  7:03                           ` Jiri Slaby
2019-08-15  5:02                           ` Daniel Drake
2019-08-12  7:46                         ` Li, Aubrey
2019-08-12 12:24                           ` Thomas Gleixner
2019-08-12 12:59                             ` Aubrey Li
2019-08-12 17:11                               ` Thomas Gleixner
2019-08-19 10:37                         ` [tip:x86/urgent] " tip-bot for Thomas Gleixner
2019-08-01  9:00   ` setup_boot_APIC_clock() NULL dereference during early boot on reduced hardware platforms Daniel Drake
2019-08-01 10:17     ` Thomas Gleixner
2019-08-01  7:27 ` Thomas Gleixner

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