On Fri, 27 Jan, at 04:39:59PM, Jiri Kosina wrote:
> From: Jiri Kosina <[email protected]>
>
> Commit 129766708 ("x86/efi: Only map RAM into EFI page tables if in
> mixed-mode") stopped creating 1:1 mapping for all RAM in case of running
> in native 64bit mode.
>
> It turns out though that there are 64bit EFI implementations in the wild
> (this particular problem has been reported on Lenovo Yoga 710-11IKB) which
> still make use of first physical page for their own private use even
> though they explicitly mark it EFI_CONVENTIONAL_MEMORY in the memory map.
>
> In case there is no mapping for this particular frame in EFI pagetables,
> as soon as firmware tries to make use of it, triple fault occurs and the
> system reboots (in case of Yoga 710-11IKB this is very early during boot).
>
> Fix that by always mapping the first page of physical memory into EFI
> pagetables. We're on a safe side, as trim_bios_range() will reserve the
> first page and isolate it away from memory allocators anyway.
>
> Note: just reverting 129766708 is not enough on v4.9-rc1+ to fix the
> regression on affected hardware, as commit ab72a27da ("x86/efi:
> Consolidate region mapping logic") later made the first physical frame not
> to be mapped anyway.
>
> Fixes: 129766708 ("x86/efi: Only map RAM into EFI page tables if in
> mixed-mode")
> Cc: [email protected] # v4.8+
> Cc: Waiman Long <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: Laura Abbott <[email protected]>
> Cc: Vojtech Pavlik <[email protected]>
> Reported-by: Hanka Pavlikova <[email protected]>
> Signed-off-by: Jiri Kosina <[email protected]>
> ---
Thanks Jiri. Queued for v4.10-rc6.
