[PATCH v2 1/2] efi: esrt: use memremap not ioremap to access ESRT table in memory

[Dave Young]

On 03/01/16 at 11:30pm, Matt Fleming wrote:
> On Fri, 26 Feb, at 02:41:14PM, Matt Fleming wrote:
> > On Thu, 18 Feb, at 02:16:24PM, Peter Jones wrote:
> > > 
> > > So the question I have is: would you rather chop up regions and reserve
> > > the space, or allocate a new copy and update the configuration table
> > > (after ExitBootServices()) to point to it?  The latter makes it pretty
> > > easy to do from an API that all these drivers can use, and it makes the
> > > kexec case completely transparent.
> > > 
> > > Up to you.
> > 
> > I think it makes the most sense to chop up the regions we care about
> > (i.e. the ones we have drivers for) because not only does that save us
> > the effort of copying out the data on every kexec reboot, it also
> > prevents us from leaking each copy since we don't free them at the
> > moment.
> > 
> > Then we just need to maintain a separate list of regions to free in
> > efi_free_boot_services() or have some other way to distinguish between
> > them.
> > 
> > Oh, and save_runtime_map() would need updating to save Boot Services
> > regions too.
> 
> I have a very rough draft of patches that implement this strategy on
> the 'experiemntal/efi-memmap' branch in the EFI tree if anyone is
> curious and wants to take a look. The series will be sent out soon.
> 
> I wouldn't necessarily try running them or anything as there's a few
> things that I know are broken; ia64 build, EFI mixed mode boot,
> probably arm64 regressions.
> 
> The upshot of the patch series is that there's a whole lot of code we
> can share for manipulating memory maps between all EFI architectures
> and by fixing this "reserve boot services regions" in a generic way it
> should mean kexec under EFI on arm64 should be fairly trivial to
> implement, along with ESRT, etc.

Matt, thanks. One question is for the acpi patches you sent before, do you
think they are still necessary as a fix for the bgrt problem and coexist
with the "reserve useful boot services" proposal?

Thanks
Dave