Messages in this thread | | | Date | Wed, 29 Apr 2015 18:06:59 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86, amd: Set X86_FEATURE_EXTD_APICID for future processors |
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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. --
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