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From: Thomas Gleixner <tglx@linutronix.de>
To: Aubrey Li <aubrey.intel@gmail.com>
Cc: Daniel Drake <drake@endlessm.com>,
	x86@kernel.org, "Li, Aubrey" <aubrey.li@linux.intel.com>,
	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 10:13:31 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1908011011250.1788@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CAERHkrtaVAQHDU1cj2_GLL59LPjp7E=3X0Zna0spfFB=Ve5__w@mail.gmail.com>

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.

Thanks,

	tglx

  reply	other threads:[~2019-08-01  8:13 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 [this message]
2019-08-01  8:21         ` Li, Aubrey
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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