As per Intel TDX Virtual Firmware Design Guide, sec 4.3.5 and sec 9.4, all unused CPUs are put in spinning state by TDVF until OS requests for CPU bring-up via mailbox address passed by ACPI MADT table. Since by default all unused CPUs are always in spinning state, there is no point in supporting dynamic CPU online/offline feature. So current generation of TDVF does not support CPU hotplug feature. It may be supported in next generation.
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppusw...@linux.intel.com> Reviewed-by: Andi Kleen <a...@linux.intel.com> --- arch/x86/kernel/tdx.c | 14 ++++++++++++++ arch/x86/kernel/topology.c | 3 ++- 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c index 8d1d7555fb56..a36b6ae14942 100644 --- a/arch/x86/kernel/tdx.c +++ b/arch/x86/kernel/tdx.c @@ -387,6 +387,17 @@ static int tdx_handle_mmio(struct pt_regs *regs, struct ve_info *ve) return insn.length; } +static int tdx_cpu_offline_prepare(unsigned int cpu) +{ + /* + * Per Intel TDX Virtual Firmware Design Guide, + * sec 4.3.5 and sec 9.4, Hotplug is not supported + * in TDX platforms. So don't support CPU + * offline feature once its turned on. + */ + return -EOPNOTSUPP; +} + void __init tdx_early_init(void) { if (!cpuid_has_tdx_guest()) @@ -399,6 +410,9 @@ void __init tdx_early_init(void) pv_ops.irq.safe_halt = tdx_safe_halt; pv_ops.irq.halt = tdx_halt; + cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "tdx:cpu_hotplug", + NULL, tdx_cpu_offline_prepare); + pr_info("TDX guest is initialized\n"); } diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c index f5477eab5692..d879ea96d79c 100644 --- a/arch/x86/kernel/topology.c +++ b/arch/x86/kernel/topology.c @@ -34,6 +34,7 @@ #include <linux/irq.h> #include <asm/io_apic.h> #include <asm/cpu.h> +#include <asm/tdx.h> static DEFINE_PER_CPU(struct x86_cpu, cpu_devices); @@ -130,7 +131,7 @@ int arch_register_cpu(int num) } } } - if (num || cpu0_hotpluggable) + if ((num || cpu0_hotpluggable) && !is_tdx_guest()) per_cpu(cpu_devices, num).cpu.hotpluggable = 1; return register_cpu(&per_cpu(cpu_devices, num).cpu, num); -- 2.25.1