Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH v7 6/9] x86/smpboot: Support parallel startup of secondary CPUs | Date | Wed, 08 Feb 2023 14:13:18 +0100 |
| |
On Wed, Feb 08 2023 at 00:09, Brian Gerst wrote: > On Tue, Feb 7, 2023 at 6:10 PM Usama Arif <usama.arif@bytedance.com> wrote: >> Introduce a global variable 'smpboot_control' indicating to the AP how >> it should find its APIC ID. For a serialized bringup, the APIC ID is >> explicitly passed in the low bits of smpboot_control, while for parallel >> mode there are flags directing the AP to find its APIC ID in CPUID leaf >> 0x0b (for X2APIC mode) or CPUID leaf 0x01 where 8 bits are sufficient. > > For the serialized bringup case, it would be simpler to just put the > cpu number in the lower bits instead of the APIC id, skipping the > lookup.
Yes and no. It can be done, but I rather prefer the consistency of the data and the mechanism. The "overhead" or "win" is not even measurable.
Thanks,
tglx
| |