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SubjectRe: [PATCH] x86/xen/smp_pv: Register the boot CPU APIC properly
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On 02.05.24 16:39, Thomas Gleixner wrote:
> The topology core expects the boot APIC to be registered from earhy APIC
> detection first and then again when the firmware tables are evaluated. This
> is used for detecting the real BSP CPU on a kexec kernel.
>
> The recent conversion of XEN/PV to register fake APIC IDs failed to
> register the boot CPU APIC correctly as it only registers it once. This
> causes the BSP detection mechanism to trigger wrongly:
>
> CPU topo: Boot CPU APIC ID not the first enumerated APIC ID: 0 > 1
>
> Additionally this results in one CPU being ignored.
>
> Register the boot CPU APIC twice so that the XEN/PV fake enumeration
> behaves like real firmware.
>
> Reported-by: Juergen Gross <jgross@suse.com>
> Fixes: e75307023466 ("x86/xen/smp_pv: Register fake APICs")
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Tested-by: Juergen Gross <jgross@suse.com>

Reviewed-by: Juergen Gross <jgross@suse.com>

Thanks for the patch, I'll take it via the Xen tree.


Juergen

> ---
> arch/x86/xen/smp_pv.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> --- a/arch/x86/xen/smp_pv.c
> +++ b/arch/x86/xen/smp_pv.c
> @@ -154,9 +154,9 @@ static void __init xen_pv_smp_config(voi
> u32 apicid = 0;
> int i;
>
> - topology_register_boot_apic(apicid++);
> + topology_register_boot_apic(apicid);
>
> - for (i = 1; i < nr_cpu_ids; i++)
> + for (i = 0; i < nr_cpu_ids; i++)
> topology_register_apic(apicid++, CPU_ACPIID_INVALID, true);
>
> /* Pretend to be a proper enumerated system */


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