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From: Baoquan He <bhe@redhat.com>
To: Dave Young <dyoung@redhat.com>
Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de,
	mingo@kernel.org, bp@alien8.de, hpa@zytor.com,
	kirill.shutemov@linux.intel.com, x86@kernel.org
Subject: Re: [PATCH v4 3/3] x86/kdump/64: Change the upper limit of crashkernel reservation
Date: Thu, 23 May 2019 11:15:41 +0800	[thread overview]
Message-ID: <20190523031541.GD3805@MiWiFi-R3L-srv> (raw)
In-Reply-To: <20190522031133.GA31269@dhcp-128-65.nay.redhat.com>

On 05/22/19 at 11:11am, Dave Young wrote:
> >  /*
> > - * Keep the crash kernel below this limit.  On 32 bits earlier kernels
> > - * would limit the kernel to the low 512 MiB due to mapping restrictions.
> > + * Keep the crash kernel below this limit.
> > + *
> > + * On 32 bits earlier kernels would limit the kernel to the low
> > + * 512 MiB due to mapping restrictions.
> > + *
> > + * On 64bit, old kexec-tools need to be under 896MiB. The later
> > + * supports to put kernel above 4G, up to system RAM top. Here
> 
> Above two lines are not reflected in code because we have removed
> the 896M limitation, it would be better to drop the two lines to
> avoid confusion. 

Missed these comments at bottom of mail.

Yes, will remove these two lines.

> 
> > + * kdump kernel need be restricted to be under 64TB, which is
> > + * the upper limit of system RAM in 4-level paing mode. Since
> > + * the kdump jumping could be from 5-level to 4-level, the jumping
> > + * will fail if kernel is put above 64TB, and there's no way to
> > + * detect the paging mode of the kernel which will be loaded for
> > + * dumping during the 1st kernel bootup.
> >   */
> >  #ifdef CONFIG_X86_32
> >  # define CRASH_ADDR_LOW_MAX	SZ_512M
> >  # define CRASH_ADDR_HIGH_MAX	SZ_512M
> >  #else
> >  # define CRASH_ADDR_LOW_MAX	SZ_4G
> > -# define CRASH_ADDR_HIGH_MAX	MAXMEM
> > +# define CRASH_ADDR_HIGH_MAX	(64UL << 40)
> 
> Maybe add a new macro in sizes.h like SZ_64T

I am fine, will add and use it here. Thanks.

      parent reply	other threads:[~2019-05-23  3:15 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-09  1:36 [PATCH v4 0/3] Add restrictions for kexec/kdump jumping between 5-level and 4-level kernel Baoquan He
2019-05-09  1:36 ` [PATCH v4 1/3] x86/boot: Add xloadflags bits for 5-level kernel checking Baoquan He
2019-05-09  1:36 ` [PATCH v4 2/3] x86/kexec/64: Error out if try to jump to old 4-level kernel from 5-level kernel Baoquan He
2019-05-09  7:01   ` Baoquan He
2019-05-09  7:02   ` [PATCH v5 " Baoquan He
2019-05-22  3:20   ` [PATCH v4 " Dave Young
2019-05-22  3:24     ` Dave Young
2019-05-22  4:50     ` Baoquan He
2019-05-09  1:36 ` [PATCH v4 3/3] x86/kdump/64: Change the upper limit of crashkernel reservation Baoquan He
2019-05-22  3:11   ` Dave Young
2019-05-22  3:15     ` Baoquan He
2019-05-23  3:15     ` Baoquan He [this message]

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