Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [patch v3 31/36] x86/apic: Provide cpu_primary_thread mask | Date | Fri, 26 May 2023 12:14:21 +0200 |
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On Wed, May 24 2023 at 23:48, Kirill A. Shutemov wrote: > On Mon, May 08, 2023 at 09:44:17PM +0200, Thomas Gleixner wrote: >> #ifdef CONFIG_SMP >> -/** >> - * apic_id_is_primary_thread - Check whether APIC ID belongs to a primary thread >> - * @apicid: APIC ID to check >> - */ >> -bool apic_id_is_primary_thread(unsigned int apicid) >> +static void cpu_mark_primary_thread(unsigned int cpu, unsigned int apicid) >> { >> - u32 mask; >> - >> - if (smp_num_siblings == 1) >> - return true; >> /* Isolate the SMT bit(s) in the APICID and check for 0 */ >> - mask = (1U << (fls(smp_num_siblings) - 1)) - 1; >> - return !(apicid & mask); >> + u32 mask = (1U << (fls(smp_num_siblings) - 1)) - 1; >> + >> + if (smp_num_siblings == 1 || !(apicid & mask)) >> + cpumask_set_cpu(cpu, &__cpu_primary_thread_mask); >> } >> +#else >> +static inline void cpu_mark_primary_thread(unsigned int cpu, unsigned int apicid) { } >> #endif >> >> /* > > This patch causes boot regression on TDX guest. The guest crashes on SMP > bring up.
I rather call it a security feature: It makes TDX unbreakably secure.
> The change makes use of smp_num_siblings earlier than before: the mask get > constructed in acpi_boot_init() codepath. Later on smp_num_siblings gets > updated in detect_ht(). > > In my setup with 16 vCPUs, smp_num_siblings is 16 before detect_ht() and > set to 1 in detect_ht().
early_init_intel(c) if (detect_extended_topology_early(c) < 0) detect_ht_early(c);
acpi_boot_init() ....
identify_boot_cpu(c) detect_ht(c);
Aaargh. That whole CPU identification code is a complete horrorshow.
I'll have a look....
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