Messages in this thread Patch in this message | | | From | Kuppuswamy Sathyanarayanan <> | Subject | [PATCH v3 3/5] x86/topology: Disable CPU online/offline control for TDX guest | Date | Mon, 19 Jul 2021 21:08:59 -0700 |
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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.kuppuswamy@linux.intel.com> Reviewed-by: Andi Kleen <ak@linux.intel.com> Reviewed-by: Tony Luck <tony.luck@intel.com> ---
Changes since v1: * Replaced is_tdx_guest() check with prot_guest_has(PR_GUEST_TDX).
arch/x86/kernel/tdx.c | 15 +++++++++++++++ arch/x86/kernel/topology.c | 3 ++- 2 files changed, 17 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c index 92acccbce59c..a110bd5e5e4c 100644 --- a/arch/x86/kernel/tdx.c +++ b/arch/x86/kernel/tdx.c @@ -5,6 +5,7 @@ #define pr_fmt(fmt) "x86/tdx: " fmt #include <linux/protected_guest.h> +#include <linux/cpuhotplug.h> #include <asm/tdx.h> #include <asm/vmx.h> @@ -306,6 +307,17 @@ static int tdg_handle_mmio(struct pt_regs *regs, struct ve_info *ve) return insn.length; } +static int tdg_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 it is turned on. + */ + return -EOPNOTSUPP; +} + unsigned long tdg_get_ve_info(struct ve_info *ve) { u64 ret; @@ -446,5 +458,8 @@ void __init tdx_early_init(void) pv_ops.irq.safe_halt = tdg_safe_halt; pv_ops.irq.halt = tdg_halt; + cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "tdg:cpu_hotplug", + NULL, tdg_cpu_offline_prepare); + pr_info("Guest initialized\n"); } diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c index bd83748e2bde..7b5fab69d56e 100644 --- a/arch/x86/kernel/topology.c +++ b/arch/x86/kernel/topology.c @@ -32,6 +32,7 @@ #include <linux/init.h> #include <linux/smp.h> #include <linux/irq.h> +#include <linux/protected_guest.h> #include <asm/io_apic.h> #include <asm/cpu.h> @@ -130,7 +131,7 @@ int arch_register_cpu(int num) } } } - if (num || cpu0_hotpluggable) + if ((num || cpu0_hotpluggable) && !prot_guest_has(PR_GUEST_TDX)) per_cpu(cpu_devices, num).cpu.hotpluggable = 1; return register_cpu(&per_cpu(cpu_devices, num).cpu, num); -- 2.25.1
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