On 4/30/25 14:33, Thomas Gleixner wrote:
> On Wed, Apr 30 2025 at 09:14, Roman Kisel wrote:
>> -static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip)
>> +static int wakeup_cpu_via_vmgexit(u32 apic_id, unsigned long start_ip, int
>> cpu)
>
> unsigned int cpu please. There are no negative CPU numbers yet :)
>
>> {
>> struct sev_es_save_area *cur_vmsa, *vmsa;
>> struct ghcb_state state;
>> @@ -1187,7 +1187,7 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id,
>> unsigned long start_ip)
>> unsigned long flags;
>> struct ghcb *ghcb;
>> u8 sipi_vector;
>> - int cpu, ret;
>> + int ret;
>> u64 cr4;
>>
>> /*
>> @@ -1208,15 +1208,6 @@ static int wakeup_cpu_via_vmgexit(u32 apic_id,
>> unsigned long start_ip)
>>
>> /* Override start_ip with known protected guest start IP */
>> start_ip = real_mode_header->sev_es_trampoline_start;
>> -
>> - /* Find the logical CPU for the APIC ID */
>> - for_each_present_cpu(cpu) {
>> - if (arch_match_cpu_phys_id(cpu, apic_id))
>> - break;
>> - }
>> - if (cpu >= nr_cpu_ids)
>> - return -EINVAL;
>> -
>
> I just looked what arch_match_cpu_phys_id() actually does and I couldn't
> help myself to get a fit of laughter. x86 uses the weak default function
> in drivers/of/cpu.c:
>
> bool __weak arch_match_cpu_phys_id(int cpu, u64 phys_id)
> {
> return (u32)phys_id == cpu;
> }
There is an x86 version of this function in arch/x86/kernel/cpu/topology.c
that overrides the __weak definition and does:
bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
{
return phys_id == (u64)cpuid_to_apicid[cpu];
}
Thanks,
Tom
>
> So this loop is the most convoluted way to write:
>
> cpu = apic_id;
>
> which is valid because the to be started CPU must be present, no?
>
> I'm not opposed against the CPU number argument per se, but the
> justification for it is dubious at best.
>
> Thanks,
>
> tglx
