linux-kernel - Re: Regression (ARM) arch/arm/mm/init.c doesn't build without CONFIG_ARM_PATCH_PHYS

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Date:	Mon, 06 Jan 2014 23:08:50 +0100
From:	khalasa@...p.pl (Krzysztof Hałasa)
To:	Santosh Shilimkar <santosh.shilimkar@...com>
Cc:	Russell King <rmk+kernel@....linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: Regression (ARM) arch/arm/mm/init.c doesn't build without CONFIG_ARM_PATCH_PHYS_VIRT.

Santosh Shilimkar <santosh.shilimkar@...com> writes:

> I am afraid you didn't understood what the fix is if you say above.
> arm_dma_limit is broken without this fix for LPAE machines with
> memory starting 4 GB physical boundary.

I wonder what CONFIG_ARM_PATCH_PHYS_VIRT and CONFIG_ZONE_DMA do they
use?

Of course, CONFIG_ZONE_DMA must be set, because otherwise the patch
changes a part disabled with #ifdef. CONFIG_ARM_PATCH_PHYS_VIRT must be
set because otherwise the kernel will not compile at all.

Do you accept the fact the configurations with CONFIG_ZONE_DMA and
without CONFIG_ARM_PATCH_PHYS_VIRT are now broken - by this very commit?

Now, what "fix" does this commit in its entirety do:

-     arm_dma_limit = PHYS_OFFSET + arm_dma_zone_size - 1;
+     arm_dma_limit = __pv_phys_offset + arm_dma_zone_size - 1;

if under the above circumstances (CONFIG_*) in
arch/arm/include/asm/memory.h we have:

extern u64 __pv_phys_offset;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the only usable declaration of this variable
extern u64 __pv_offset;
extern void fixup_pv_table(const void *, unsigned long);
extern const void *__pv_table_begin, *__pv_table_end;

#define PHYS_OFFSET __pv_phys_offset
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-- 
Krzysztof Halasa

Research Institute for Automation and Measurements PIAP
Al. Jerozolimskie 202, 02-486 Warsaw, Poland
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