[PATCH v3 3/7] arm64: split off early mapping code from early_fixmap_init()

[will.deacon@arm.com (Will Deacon)]

On Tue, Dec 08, 2015 at 02:29:33PM +0100, Ard Biesheuvel wrote:
> On 8 December 2015 at 13:40, Will Deacon <will.deacon@arm.com> wrote:
> > On Thu, Dec 03, 2015 at 12:18:40PM +0000, Mark Rutland wrote:
> >> Apologies that it's taken me so long to get around to this...
> >>
> >> On Mon, Nov 16, 2015 at 12:23:14PM +0100, Ard Biesheuvel wrote:
> >> > This splits off and generalises the population of the statically
> >> > allocated fixmap page tables so that we may reuse it later for
> >> > the linear mapping once we move the kernel text mapping out of it.
> >> >
> >> > This also involves taking into account that table entries at any of
> >> > the levels we are populating may have been populated already, since
> >> > the fixmap mapping might not be disjoint up to the pgd level anymore
> >> > from other early mappings.
> >>
> >> As a heads-up, for avoiding TLB conflicts, I'm currently working on
> >> alternative way of creating the kernel page tables which will definitely
> >> conflict here, and may or may not supercede this approach.
> >
> > Given that the Christmas break is around the corner and your TLB series
> > is probably going to take some time to get right, I suggest we persevere
> > with Ard's current patch series for 4.5 and merge the TLB conflict solution
> > for 4.6. I don't want us to end up in a situation where this is needlessly
> > blocked on something that isn't quite ready.
> >
> > Any objections? If not, Ard -- can you post a new version of this, please?
> >
> 
> Happy to post a new version, with the following remarks
> - my current private tree has evolved in the mean time, and I am now
> putting the kernel image at the base of the vmalloc region (and the
> module region right before)
> - I think Mark's changes would allow me to deobfuscate the VA bias
> that redirects __va() translations into the kernel VA space rather
> than the linear mapping

I'll leave that up to you. I'm just trying to avoid you growing a dependency
on something that's unlikely to make it for 4.5. If Mark separates out the
parts you need, perhaps that offers us some middle ground.

Will