From: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx> Sent: Thursday, February 1, 2024 11:13 PM
>
> Currently, the secondary CPUs in Hyper-V VTL context lack support for
> parallel startup. Therefore, relying on the single initial_stack fetched
> from the current task structure suffices for all vCPUs.
>
> However, common initial_stack risks stack corruption when parallel startup
> is enabled. In order to facilitate parallel startup, use the initial_stack
> from the per CPU idle thread instead of the current task.
>
> Fixes: 18415f33e2ac ("cpu/hotplug: Allow "parallel" bringup up to CPUHP_BP_KICK_AP_STATE")
> Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
> ---
> arch/x86/hyperv/hv_vtl.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
> index 96e6c51515f5..b0ab724def17 100644
> --- a/arch/x86/hyperv/hv_vtl.c
> +++ b/arch/x86/hyperv/hv_vtl.c
> @@ -12,6 +12,7 @@
> #include <asm/i8259.h>
> #include <asm/mshyperv.h>
> #include <asm/realmode.h>
> +#include <../kernel/smpboot.h>
>
> extern struct boot_params boot_params;
> static struct real_mode_header hv_vtl_real_mode_header;
> @@ -57,7 +58,7 @@ static void hv_vtl_ap_entry(void)
> ((secondary_startup_64_fn)secondary_startup_64)(&boot_params, &boot_params);
> }
>
> -static int hv_vtl_bringup_vcpu(u32 target_vp_index, u64 eip_ignored)
> +static int hv_vtl_bringup_vcpu(u32 target_vp_index, int cpu, u64 eip_ignored)
> {
> u64 status;
> int ret = 0;
> @@ -71,7 +72,8 @@ static int hv_vtl_bringup_vcpu(u32 target_vp_index, u64 eip_ignored)
> struct ldttss_desc *ldt;
> struct desc_struct *gdt;
>
> - u64 rsp = current->thread.sp;
> + struct task_struct *idle = idle_thread_get(cpu);
> + u64 rsp = (unsigned long)idle->thread.sp;
> u64 rip = (u64)&hv_vtl_ap_entry;
>
> native_store_gdt(&gdt_ptr);
> @@ -198,7 +200,15 @@ static int hv_vtl_apicid_to_vp_id(u32 apic_id)
>
> static int hv_vtl_wakeup_secondary_cpu(u32 apicid, unsigned long start_eip)
> {
> - int vp_id;
> + int vp_id, cpu;
> +
> + /* Find the logical CPU for the APIC ID */
> + for_each_present_cpu(cpu) {
> + if (arch_match_cpu_phys_id(cpu, apicid))
> + break;
> + }
> + if (cpu >= nr_cpu_ids)
> + return -EINVAL;
>
> pr_debug("Bringing up CPU with APIC ID %d in VTL2...\n", apicid);
> vp_id = hv_vtl_apicid_to_vp_id(apicid);
> @@ -212,7 +222,7 @@ static int hv_vtl_wakeup_secondary_cpu(u32 apicid, unsigned long start_eip)
> return -EINVAL;
> }
>
> - return hv_vtl_bringup_vcpu(vp_id, start_eip);
> + return hv_vtl_bringup_vcpu(vp_id, cpu, start_eip);
> }
>
> int __init hv_vtl_early_init(void)
> --
> 2.34.1
>
Reviewed-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
