lkml.org 
[lkml]   [2015]   [Apr]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] x86, amd: Set X86_FEATURE_EXTD_APICID for future processors
On Mon, Apr 27, 2015 at 10:25:51AM -0500, Aravind Gopalakrishnan wrote:
> Decision to use a 4-bit mask or 8-bit mask in default_get_apic_id()
> is controlled by setting capability bit X86_FEATURE_EXTD_APICID.
>
> Currently, we detect extended APIC ID support by accessing Link
> Transaction Control register D18F0x68 in PCI config space.
>
> But, not even that is needed as we can safely postulate that future
> AMD processors will support 8-bit APIC IDs and we can simply set that
> feature bit on them, without the PCI access.
>
> Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>
> ---
> arch/x86/kernel/cpu/amd.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index fd470eb..20b6813 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -520,8 +520,16 @@ static void early_init_amd(struct cpuinfo_x86 *c)
> set_cpu_cap(c, X86_FEATURE_K6_MTRR);
> #endif
> #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_PCI)
> - /* check CPU config space for extended APIC ID */
> - if (cpu_has_apic && c->x86 >= 0xf) {
> + /*
> + * ApicID can always be treated as a 8bit value for
> + * AMD APIC versions >= 0x10. So, we can safely set

Expanded the version aspect to:

/*
* ApicID can always be treated as a 8bit value for AMD APIC versions
* >= 0x10 but even old K8s came out of reset with version 0x10. So, we
* can safely set X86_FEATURE_EXTD_APICID unconditionally for families
* after 16h.
*/

and applied.

Thanks.

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
--


\
 
 \ /
  Last update: 2015-04-29 18:21    [W:0.441 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site