From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Nicolas Pitre <nico@fluxnic.net>
Cc: Wang Nan <wangnan0@huawei.com>,
kexec@lists.infradead.org, Eric Biederman <ebiederm@xmission.com>,
Andrew Morton <akpm@linux-foundation.org>,
Geng Hui <hui.geng@huawei.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
stable@vger.kernel.org
Subject: Re: [PATCH 3/3] ARM: allow kernel to be loaded in middle of phymem
Date: Thu, 23 Jan 2014 19:31:37 +0000 [thread overview]
Message-ID: <20140123193137.GA15937@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <alpine.LFD.2.11.1401231357520.1652@knanqh.ubzr>
On Thu, Jan 23, 2014 at 02:15:07PM -0500, Nicolas Pitre wrote:
> On Wed, 22 Jan 2014, Wang Nan wrote:
>
> > This patch allows the kernel to be loaded at the middle of kernel awared
> > physical memory. Before this patch, users must use mem= or device tree to cheat
> > kernel about the start address of physical memory.
> >
> > This feature is useful in some special cases, for example, building a crash
> > dump kernel. Without it, kernel command line, atag and devicetree must be
> > adjusted carefully, sometimes is impossible.
>
> With CONFIG_PATCH_PHYS_VIRT the value for PHYS_OFFSET is determined
> dynamically by rounding down the kernel image start address to the
> previous 16MB boundary. In the case of a crash kernel, this might be
> cleaner to simply readjust __pv_phys_offset during early boot and call
> fixup_pv_table(), and then reserve away the memory from the previous
> kernel. That will let you access that memory directly (with gdb for
> example) and no pointer address translation will be required.
We already have support in the kernel to ignore memory below the calculated
PHYS_OFFSET. See 571b14375019c3a66ef70d4d4a7083f4238aca30.
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next prev parent reply other threads:[~2014-01-23 19:32 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-22 11:25 [PATCH 0/3] Bugfix for kdump on arm Wang Nan
2014-01-22 11:25 ` [PATCH 1/3] ARM: Premit ioremap() to map reserved pages Wang Nan
2014-01-22 11:38 ` Will Deacon
2014-01-22 11:42 ` Russell King - ARM Linux
2014-01-22 11:55 ` Wang Nan
2014-01-22 11:25 ` [PATCH 2/3] ARM: kexec: copying code to ioremapped area Wang Nan
2014-01-22 12:56 ` Vaibhav Bedia
2014-01-22 13:03 ` Wang Nan
2014-01-22 13:27 ` Russell King - ARM Linux
2014-01-23 2:16 ` Wang Nan
2014-01-22 11:25 ` [PATCH 3/3] ARM: allow kernel to be loaded in middle of phymem Wang Nan
2014-01-23 19:15 ` Nicolas Pitre
2014-01-23 19:31 ` Russell King - ARM Linux [this message]
2014-01-23 20:01 ` Nicolas Pitre
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