Re: [tip:efi/core] x86/efi: Unmap EFI boot services code/data regions from efi_pgd

[Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>]

On Mon, 17 Dec 2018 at 19:42, Prakhya, Sai Praneeth
<sai.praneeth.prakhya@xxxxxxxxx> wrote:
>
> > > Hi Thomas and Ingo,
> > >
> > > I recently noticed that the below commits [1] and [2] are broken when
> > > kernel command line argument "efi=old_map" is passed. Sorry! I missed
> > > to test this condition prior to sending these patches to mailing list.
> > > I am working on a fix and will send it to mailing list as soon as it's ready.
> > >
> >
> > Could you elaborate on the problem please?
>
> Sure! My bad..
>
> Little bit of history here:
> Boris with this patch set [1] introduced statically mapping EFI Runtime Services at -4G
> and also introduced "efi=old_map" to return to previous EFI functionality which used
> ioremap and __va(pa).
>
> [3] and [4] are links to old_map_region()
>
> The commit 08cfb38f3ef4 ("x86/efi: Unmap EFI boot services code/data regions from efi_pgd"),
> unmaps EFI boot services code/data regions *only* from efi_pgd but efi=old_map maps
> EFI boot services code/data regions into swapper_pgd. Also, efi=old_map  uses either
> ioremap() or __va(md->phys_addr) to map EFI runtime/boot time services and doesn't use kernel_map_pages_in_pgd().
>
> So, we need a different unmapping routine to unmap EFI boot services code/data
> regions from swapper_pgd if they were mapped using efi=old_map.
>

For the short term, could we simply make your changes dependent on efi
!= old_map? That gives us some time to fix the old_map case properly.