Re: [Xen-devel] [PATCH v2 0/4] xen: arm: various improvements to boot time page table handling

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2014-07-18 at 17:36 +0100, Andrew Cooper wrote:
> On 18/07/14 17:30, Ian Campbell wrote:
> > On Fri, 2014-07-18 at 17:16 +0100, Ian Campbell wrote:
> >> On Fri, 2014-07-18 at 17:11 +0100, Ian Campbell wrote:
> >>> Since v2 I've made it correctly handle being loaded at exactly 2M (so
> >>> virt == phys on boot) and made a few cleanups.
> >>>
> >>> I've also tested with various offsets from the base of RAM:
> >>>         0x00200000 (2M)
> >>>         0x40000000 (1G)
> >>>         0x40200000 (1G+2M)
> >>>         0x80000000 (2G)
> >>>         0x80400000 (2G+4M)
> >>>         0x80401000 (2G+4M+2K)
> >>>
> >>> On Midway (RAM starts at 0) and XGene (RAM starts at 256G). I think this
> >>> covers the interesting cases at each level except the zeroeth where I
> >>> have no hardware to test anything other than mappings in slot 0. I also
> >>> couldn't test virt==phys on 64 bit since I've no such systems with RAM
> >>> at 0.
> >> I just realised that I forgot to add the check that head.S fits in 4K.
> >> I'll do that in a patch 5/4 shortly.
> > On second thoughts... This requires some sort of compile or link time
> > error/assertion in either gnu as or ld based on the offset of a symbol
> > or size of a section etc. I can't find anything in either manual which
> > would allow this to be constructed
> >
> > So I'm going to punt on this. Right now aem64/head.o is 1824 bytes and
> > arm32/head.o is 1920 bytes, so neither are even half way to blowing this
> > limit (which is an upper bound since the real limit is the offset of the
> > symbol "paging", at 1116 and 1196 bytes respectively).
> >
> > If someone can come up with a suitable construct then we can revisit
> > this.
> >
> > Ian.
> 
> If I understand your problem correctly, it is exactly the same as we do
> for the kexec relocation page in x86.
> 
> See the bottom of xen/arch/x86/xen.lds.S

That's the badger!

Thanks. It's in "Other Linker Script Commands" in the docs rather than
somewhere I was capable of finding it without knowing  the name...

Ian.



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel