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Re: [Xen-devel] Physical memory start contraints in the Linux kernel (Was: Re: Xen osstest on Calxeda midway progress (Was: Re: [xen-unstable test] 21486: tolerable FAIL - PUSHED))
- To: Julien Grall <julien.grall@xxxxxxxxxx>
- From: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>
- Date: Tue, 12 Nov 2013 14:41:28 +0000
- Cc: Andre Przywara <andre.przywara@xxxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>, "xen.org" <ian.jackson@xxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>, Olof Johansson <olof@xxxxxxxxx>, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
- Delivery-date: Tue, 12 Nov 2013 14:41:56 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On Tue, Nov 12, 2013 at 02:35:10PM +0000, Julien Grall wrote:
> During some debugging on the Arndale and Midway, I found another
> constraint with CONFIG_ARM_PATCH_PHYS_VIRT.
> I have noticed that all the kernel physical addresses must be lower than
> the corresponding virtual addresses. So the delta offset compute in
> __fixup_pv_table (arch/arm/kernel/head.S) must always be negative.
> If this assertion is not validated, when the kernel will browse the
> memory bank (sanity_check_info in arch/arm/mm/mmu.c), __phys(...) will
> compute a wrong address and will result to consider all memory bank as
> highmem.
>
> After digging in the code, it seems it's due to some optimization during
> opcode fixup in __fixup_a_pvtable. Is it a wanted constraint?
Are you talking about the code in v3.12 or the code in -next ?
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