lkml.org 
[lkml]   [2018]   [Feb]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: x86/microcode/intel: Division by zero panic in 4.9.79 and 4.4.114
On Wed, Feb 7, 2018 at 6:12 PM, Borislav Petkov <bp@alien8.de> wrote:
> On Wed, Feb 07, 2018 at 04:31:59PM +0000, Rolf Neugebauer wrote:
>> arch/x86/kernel/cpu/microcode/core.c | 28 +++++++++++++++++++---------
>> 1 file changed, 19 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/microcode/core.c
>> b/arch/x86/kernel/cpu/microcode/core.c
>> index b3e94ef461fd..1b3e0aa4c511 100644
>> --- a/arch/x86/kernel/cpu/microcode/core.c
>> +++ b/arch/x86/kernel/cpu/microcode/core.c
>> @@ -44,7 +44,7 @@
>>
>> static struct microcode_ops *microcode_ops;
>>
>> -static bool dis_ucode_ldr;
>> +static bool dis_ucode_ldr = true;
>>
>> static int __init disable_loader(char *str)
>> {
>> @@ -81,6 +81,7 @@ struct cpu_info_ctx {
>>
>> static bool __init check_loader_disabled_bsp(void)
>> {
>> + u32 a, b, c, d;
>> #ifdef CONFIG_X86_32
>> const char *cmdline = (const char *)__pa_nodebug(boot_command_line);
>> const char *opt = "dis_ucode_ldr";
>> @@ -93,8 +94,23 @@ static bool __init check_loader_disabled_bsp(void)
>> bool *res = &dis_ucode_ldr;
>> #endif
>>
>> - if (cmdline_find_option_bool(cmdline, option))
>> - *res = true;
>> + if (!have_cpuid_p())
>> + return *res;
>
> That might cause an issue, see 1f161f67a272c. Might wanna backport that
> commit too, just in case, for those old CPUID-less geodes.

On the 4.4 kernel, 1f161f67a272c ("x86/microcode: Do the family check
first") does not apply cleanly. Looks like it relies on 309aac77768c0
("x86/microcode: Decrease CPUID use") and 7a93a40be23e5
("x86/microcode: Remove local vendor variable") as well. These don't
apply cleanly either.

Should I just manually backport the functionality of 1f161f67a272c?

Rolf

>
> The rest looks ok.
>
> --
> Regards/Gruss,
> Boris.
>
> Good mailing practices for 400: avoid top-posting and trim the reply.

\
 
 \ /
  Last update: 2018-02-08 14:56    [W:0.082 / U:0.356 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site