Re: [PATCH] efi: runtime: avoid EFIv2 runtime services on Apple x86 machines

[Aditya Garg <gargaditya08@live.com>]

> On 12-Jan-2022, at 3:44 PM, Ard Biesheuvel <ardb@kernel.org> wrote:
> 
> Aditya reports [0] that his recent MacbookPro crashes in the firmware
> when using the variable services at runtime. The culprit appears to be a
> call to QueryVariableInfo(), which we did not use to call on Apple x86
> machines in the past as they only upgraded from EFI v1.10 to EFI v2.40
> firmware fairly recently, and QueryVariableInfo() (along with
> UpdateCapsule() et al) was added in EFI v2.00.
> 
> The only runtime service introduced in EFI v2.00 that we actually use in
> Linux is QueryVariableInfo(), as the capsule based ones are optional,
> generally not used at runtime (all the LVFS/fwupd firmware update
> infrastructure uses helper EFI programs that invoke capsule update at
> boot time, not runtime), and not implemented by Apple machines in the
> first place. QueryVariableInfo() is used to 'safely' set variables,
> i.e., only when there is enough space. This prevents machines with buggy
> firmwares from corrupting their NVRAMs when they run out of space.
> 
> Given that Apple machines have been using EFI v1.10 services only for
> the longest time (the EFI v2.0 spec was released in 2006, and Linux
> support for the newly introduced runtime services was added in 2011, but
> the MacbookPro12,1 released in 2015 still claims to be EFI v1.10 only),
> let's avoid the EFI v2.0 ones on all Apple x86 machines.
> 
> [0] https://lore.kernel.org/all/6D757C75-65B1-468B-842D-10410081A8E4@live.com/
> 
> Cc: <stable@vger.kernel.org>
> Cc: Jeremy Kerr <jk@ozlabs.org>
> Cc: Matthew Garrett <mjg59@srcf.ucam.org>
> Reported-by: Aditya Garg <gargaditya08@live.com>
> Tested-by: Orlando Chamberlain <redecorating@protonmail.com>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> drivers/firmware/efi/efi.c | 7 +++++++
> 1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index ae79c3300129..7de3f5b6e8d0 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -722,6 +722,13 @@ void __init efi_systab_report_header(const efi_table_hdr_t *systab_hdr,
> 		systab_hdr->revision >> 16,
> 		systab_hdr->revision & 0xffff,
> 		vendor);
> +
> +	if (IS_ENABLED(CONFIG_X86_64) &&
> +	    systab_hdr->revision > EFI_1_10_SYSTEM_TABLE_REVISION &&
> +	    !strcmp(vendor, "Apple")) {
> +		pr_info("Apple Mac detected, using EFI v1.10 runtime services only\n");
> +		efi.runtime_version = EFI_1_10_SYSTEM_TABLE_REVISION;
> +	}
> }
> 
> static __initdata char memory_type_name[][13] = {
> -- 
> 2.30.2
> 
Hi Ard

Patch works for me. Thanks for investing time to fix the issue :)

Tested-by: Aditya Garg <gargaditya08@live.com>

You may also add the link of the Bug report

Link: https://bugzilla.kernel.org/show_bug.cgi?id=215277

Regards
Aditya