Regression (ARM) arch/arm/mm/init.c doesn't build without CONFIG_ARM_PATCH_PHYS_VIRT.

On Monday 06 January 2014 05:08 PM, Krzysztof Ha?asa wrote:

Santosh Shilimkar [off-list ref] writes:

quoted

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?

You need to grep where the CONFIG_ARM_PATCH_PHYS_VIRT is used ;)

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
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Your grep actually missed the assembly files where the actual patching
happens. Please have a look at "arch/arm/kernel/head.S"

The "CONFIG_ARM_PATCH_PHYS_VIRT" is always enabled on almost all ARM builds
since its needed for multi-config kernel to work. May be its time to
make it default enabled but I let Russell comment if there is any
better way to handle this.

Regards,
Santosh