On Wed, 4 Mar 2020 at 18:15, Arvind Sankar <nivedita@xxxxxxxxxxxx> wrote:
>
> On Wed, Mar 04, 2020 at 05:59:17PM +0100, Ard Biesheuvel wrote:
> > Commit 3a6b6c6fb23667fa ("efi: Make EFI_MEMORY_ATTRIBUTES_TABLE
> > initialization common across all architectures") moved the call to
> > efi_memattr_init() from ARM specific to generic EFI init code, in
> > order to be able to apply the restricted permissions described in
> > that table on x86 as well.
> >
> > We never enabled this feature fully on i386, and so mapping and
> > reserving this table is pointless. However, due to the early call to
> > memblock_reserve(), the memory bookkeeping gets confused to the point
> > where it produces the splat below when we try to map the memory later
> > on:
> >
> > ------------[ cut here ]------------
> > ioremap on RAM at 0x3f251000 - 0x3fa1afff
> > WARNING: CPU: 0 PID: 0 at arch/x86/mm/ioremap.c:166 __ioremap_caller ...
> > Modules linked in:
> > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.20.0 #48
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> > EIP: __ioremap_caller.constprop.0+0x249/0x260
> > Code: 90 0f b7 05 4e 38 40 de 09 45 e0 e9 09 ff ff ff 90 8d 45 ec c6 05 ...
> > EAX: 00000029 EBX: 00000000 ECX: de59c228 EDX: 00000001
> > ESI: 3f250fff EDI: 00000000 EBP: de3edf20 ESP: de3edee0
> > DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00200296
> > CR0: 80050033 CR2: ffd17000 CR3: 1e58c000 CR4: 00040690
> > Call Trace:
> > ioremap_cache+0xd/0x10
> > ? old_map_region+0x72/0x9d
> > old_map_region+0x72/0x9d
> > efi_map_region+0x8/0xa
> > efi_enter_virtual_mode+0x260/0x43b
> > start_kernel+0x329/0x3aa
> > i386_start_kernel+0xa7/0xab
> > startup_32_smp+0x164/0x168
> > ---[ end trace e15ccf6b9f356833 ]---
> >
> > Let's work around this by disregarding the memory attributes table
> > altogether on i386, which does not result in a loss of functionality
> > or protection, given that we never consumed the contents.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
>
> Thanks!
>
> Tested-by: Arvind Sankar <nivedita@xxxxxxxxxxxx>
>
Thanks. I guess nobody noticed because nobody enabled this feature on
production i386 hardware.
