On Sat, 22 Dec 2018 at 11:54, Ingo Molnar <mi...@kernel.org> wrote: > > > * Sai Praneeth Prakhya <sai.praneeth.prak...@intel.com> wrote: > > > Commit d5052a7130a6 ("x86/efi: Unmap EFI boot services code/data regions > > from efi_pgd") forgets to take two EFI modes into consideration namely > > EFI_OLD_MEMMAP and EFI_MIXED_MODE. > > So the commit sha1 ended up being this one in tip:efi/core: > > 08cfb38f3ef4: x86/efi: Unmap EFI boot services code/data regions from > efi_pgd > > > EFI_OLD_MEMMAP is a legacy way of mapping EFI regions into swapper_pg_dir > > using ioremap() and init_memory_mapping(). This feature can be enabled by > > passing "efi=old_map" as kernel command line argument. But, > > efi_unmap_pages() unmaps EFI boot services code/data regions *only* from > > efi_pgd and hence cannot be used for unmapping EFI boot services code/data > > regions from swapper_pg_dir. > > > > Introduce a temporary fix to not unmap EFI boot services code/data regions > > when EFI_OLD_MEMMAP is enabled while working on a real fix. > > > > EFI_MIXED_MODE is another feature where a 64-bit kernel runs on a > > 64-bit platform crippled by a 32-bit firmware. To support EFI_MIXED_MODE, > > all RAM (i.e. namely EFI regions like EFI_CONVENTIONAL_MEMORY, > > EFI_LOADER_<CODE/DATA>, EFI_BOOT_SERVICES_<CODE/DATA> and > > EFI_RUNTIME_CODE/DATA regions) is mapped into efi_pgd all the time to > > facilitate EFI runtime calls access it's arguments in 1:1 mode. Hence, > > don't unmap EFI boot services code/data regions when booted in mixed mode. > > > > Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prak...@intel.com> > > Cc: Borislav Petkov <b...@alien8.de> > > Cc: Ingo Molnar <mi...@kernel.org> > > Cc: Andy Lutomirski <l...@kernel.org> > > Cc: Dave Hansen <dave.han...@intel.com> > > Cc: Bhupesh Sharma <bhsha...@redhat.com> > > Cc: Peter Zijlstra <pet...@infradead.org> > > Cc: Thomas Gleixner <t...@linutronix.de> > > Cc: Ard Biesheuvel <ard.biesheu...@linaro.org> > > --- > > arch/x86/platform/efi/quirks.c | 16 ++++++++++++++++ > > 1 file changed, 16 insertions(+) > > > > diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c > > index 09e811b9da26..9c34230aaeae 100644 > > --- a/arch/x86/platform/efi/quirks.c > > +++ b/arch/x86/platform/efi/quirks.c > > @@ -380,6 +380,22 @@ static void __init efi_unmap_pages(efi_memory_desc_t > > *md) > > u64 pa = md->phys_addr; > > u64 va = md->virt_addr; > > > > + /* > > + * To Do: Remove this check after adding functionality to unmap EFI > > boot > > + * services code/data regions from direct mapping area because > > + * "efi=old_map" maps EFI regions in swapper_pg_dir. > > + */ > > + if (efi_enabled(EFI_OLD_MEMMAP)) > > + return; > > + > > + /* > > + * EFI mixed mode has all RAM mapped to access arguments while making > > + * EFI runtime calls, hence don't unmap EFI boot services code/data > > + * regions. > > + */ > > + if (!efi_is_native() && IS_ENABLED(CONFIG_EFI_MIXED))
AFAIK efi_is_native() can only return false is CONFIG_EFI_MIXED is set, so this expression can be simplified. > > + return; > > I suppose old_mmap and mixed mode stopped working altogether after the > unmapping changes? What are the symptoms, instant reboots, crasher, or > some more benign behavior like non-working runtime EFI functionality? > > If Ard acks this I'll apply it immediately, as these bugs look like > show-stoppers for merging the EFI tree into v4.21. > Acked-by: Ard Biesheuvel <ard.biesheu...@linaro.org> with the sidenote that I won't be able to test this myself until monday at the earliest.