On Sat, 22 Dec 2018 at 12:04, Ard Biesheuvel <[email protected]> wrote: > > On Sat, 22 Dec 2018 at 11:54, Ingo Molnar <[email protected]> wrote: > > > > > > * Sai Praneeth Prakhya <[email protected]> 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 <[email protected]> > > > Cc: Borislav Petkov <[email protected]> > > > Cc: Ingo Molnar <[email protected]> > > > Cc: Andy Lutomirski <[email protected]> > > > Cc: Dave Hansen <[email protected]> > > > Cc: Bhupesh Sharma <[email protected]> > > > Cc: Peter Zijlstra <[email protected]> > > > Cc: Thomas Gleixner <[email protected]> > > > Cc: Ard Biesheuvel <[email protected]> > > > --- > > > 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 <[email protected]> > > with the sidenote that I won't be able to test this myself until > monday at the earliest.
OK, so I have tested both efi=old_map and mixed mode before and after applying this patch, using QEMU/KVM with 64-bit and 32-bit builds of OVMF [respectively] efi=old_map is indeed broken before and needs this patch. Mixed mode works just fine both before and after applying the patch, but I suggest we keep this patch as-is and address mixed mode later if needed (I spotted a couple of things in the boot log that may need some attention but I'm not sure if the issue is in Linux or in OVMF)
