microsoft · ricardon · Nov 14, 2025 · Nov 14, 2025 · Nov 14, 2025 · Nov 14, 2025
diff --git a/Microsoft/hcl-x64.config b/Microsoft/hcl-x64.config
@@ -354,6 +354,7 @@ CONFIG_X86_DIRECT_GBPAGES=y
 # CONFIG_AMD_MEM_ENCRYPT is not set
 CONFIG_NUMA=y
 CONFIG_AMD_NUMA=y
+# CONFIG_X86_64_ACPI_NUMA is not set
 CONFIG_NODES_SHIFT=6
 CONFIG_ARCH_SPARSEMEM_ENABLE=y
 CONFIG_ARCH_SPARSEMEM_DEFAULT=y
@@ -433,7 +434,33 @@ CONFIG_ARCH_HAS_ADD_PAGES=y
 # CONFIG_SUSPEND is not set
 # CONFIG_PM is not set
 CONFIG_ARCH_SUPPORTS_ACPI=y
-# CONFIG_ACPI is not set
+CONFIG_ACPI=y
+# CONFIG_ACPI_DEBUGGER is not set
+# CONFIG_ACPI_SPCR_TABLE is not set
+# CONFIG_ACPI_FPDT is not set
+# CONFIG_ACPI_REV_OVERRIDE_POSSIBLE is not set
+# CONFIG_ACPI_EC_DEBUGFS is not set
+# CONFIG_ACPI_AC is not set
+# CONFIG_ACPI_BATTERY is not set
+# CONFIG_ACPI_TINY_POWER_BUTTON is not set
+# CONFIG_ACPI_DOCK is not set
+# CONFIG_ACPI_PROCESSOR is not set
+# CONFIG_ACPI_TABLE_UPGRADE is not set
+# CONFIG_ACPI_DEBUG is not set
+# CONFIG_ACPI_PCI_SLOT is not set
+# CONFIG_ACPI_CONTAINER is not set
+# CONFIG_ACPI_HOTPLUG_MEMORY is not set
+# CONFIG_ACPI_SBS is not set
+# CONFIG_ACPI_HED is not set
+# CONFIG_ACPI_REDUCED_HARDWARE_ONLY is not set
+# CONFIG_ACPI_NFIT is not set
+# CONFIG_ACPI_APEI is not set
+# CONFIG_ACPI_DPTF is not set
+# CONFIG_ACPI_CONFIGFS is not set
+# CONFIG_ACPI_PFRUT is not set
+# CONFIG_ACPI_FFH is not set
+# CONFIG_PMIC_OPREGION is not set
+# CONFIG_X86_PM_TIMER is not set
 
 #
 # CPU Frequency scaling
@@ -452,6 +479,7 @@ CONFIG_ARCH_SUPPORTS_ACPI=y
 # Bus options (PCI etc.)
 #
 CONFIG_PCI_DIRECT=y
+# CONFIG_PCI_MMCONFIG is not set
 # CONFIG_PCI_CNB20LE_QUIRK is not set
 # CONFIG_ISA_BUS is not set
 # CONFIG_ISA_DMA_API is not set
@@ -1230,6 +1258,7 @@ CONFIG_LDISC_AUTOLOAD=y
 CONFIG_SERIAL_EARLYCON=y
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_DEPRECATED_OPTIONS=y
+# CONFIG_SERIAL_8250_PNP is not set
 CONFIG_SERIAL_8250_16550A_VARIANTS=y
 # CONFIG_SERIAL_8250_FINTEK is not set
 CONFIG_SERIAL_8250_CONSOLE=y

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
@@ -1135,13 +1135,6 @@ config X86_LOCAL_APIC
 	depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
 	select IRQ_DOMAIN_HIERARCHY
 
-config X86_MAILBOX_WAKEUP
-	def_bool y
-	depends on OF || ACPI_MADT_WAKEUP
-	depends on X86_64
-	depends on SMP
-	depends on X86_LOCAL_APIC
-
 config ACPI_MADT_WAKEUP
 	def_bool y
 	depends on X86_64

diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c
@@ -6,6 +6,9 @@
  *   Saurabh Sengar <ssengar@microsoft.com>
  */
 
+#include <linux/acpi.h>
+
+#include <asm/acpi.h>
 #include <asm/apic.h>
 #include <asm/boot.h>
 #include <asm/debugreg.h>
@@ -36,18 +39,6 @@ static bool __init hv_vtl_msi_ext_dest_id(void)
 	return true;
 }
 
-static inline bool within_page(u64 addr, u64 start)
-{
-	return addr >= start && addr < (start + PAGE_SIZE);
-}
-
-static bool hv_vtl_is_private_mmio_tdx(u64 addr)
-{
-	u64 mb_addr = acpi_get_mp_wakeup_mailbox_paddr();
-
-	return mb_addr && within_page(addr, mb_addr);
-}
-
 /*
  * The `native_machine_emergency_restart` function from `reboot.c` writes
  * to the physical address 0x472 to indicate the type of reboot for the
@@ -78,10 +69,23 @@ static void  __noreturn hv_vtl_restart(char __maybe_unused *cmd)
 	hv_vtl_emergency_restart();
 }
 
+static inline bool within_page(u64 addr, u64 start)
+{
+	return addr >= start && addr < (start + PAGE_SIZE);
+}
+
+static bool hv_vtl_is_private_mmio_tdx(u64 addr)
+{
+	u64 mb_addr = acpi_get_mp_wakeup_mailbox_paddr();
+
+	return mb_addr && within_page(addr, mb_addr);
+}
+
 void __init hv_vtl_init_platform(void)
 {
 	pr_info("Linux runs in Hyper-V Virtual Trust Level\n");
 
+	x86_init.resources.probe_roms = x86_init_noop;
 	/* There is no paravisor present if we are here. */
 	if (hv_isolation_type_tdx()) {
 		x86_init.resources.realmode_limit = SZ_4G;
@@ -92,8 +96,6 @@ void __init hv_vtl_init_platform(void)
 		x86_platform.realmode_init = x86_init_noop;
 		real_mode_header = &hv_vtl_real_mode_header;
 	}
-
-	x86_init.resources.probe_roms = x86_init_noop;
 	x86_init.irqs.pre_vector_init = x86_init_noop;
 	x86_init.timers.timer_init = x86_init_noop;
 	x86_init.resources.probe_roms = x86_init_noop;
@@ -278,8 +280,8 @@ int __init hv_vtl_early_init(void)
 	 * Otherwise, use an enlightened path since SIPI is not
 	 * available for VTL2.
 	 */
-	if (!((hv_isolation_type_snp() || hv_isolation_type_tdx())
-	    && !hyperv_paravisor_present))
+	if (!((hv_isolation_type_snp() || hv_isolation_type_tdx()) &&
+	      !hyperv_paravisor_present))
 		apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu);
 
 	return 0;

diff --git a/arch/x86/include/asm/acpi.h b/arch/x86/include/asm/acpi.h
@@ -182,6 +182,10 @@ void __iomem *x86_acpi_os_ioremap(acpi_physical_address phys, acpi_size size);
 #define acpi_os_ioremap acpi_os_ioremap
 #endif
 
+void acpi_setup_mp_wakeup_mailbox(u64 addr);
+struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void);
+u64 acpi_get_mp_wakeup_mailbox_paddr(void);
+
 #else /* !CONFIG_ACPI */
 
 #define acpi_lapic 0
@@ -200,6 +204,18 @@ static inline u64 x86_default_get_root_pointer(void)
 	return 0;
 }
 
+static inline void acpi_setup_mp_wakeup_mailbox(u64 addr) { }
+
+static inline struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void)
+{
+	return NULL;
+}
+
+static inline u64 acpi_get_mp_wakeup_mailbox_paddr(void)
+{
+	return 0;
+}
+
 #endif /* !CONFIG_ACPI */
 
 #define ARCH_HAS_POWER_INIT	1

diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
@@ -152,10 +152,6 @@ static inline struct cpumask *cpu_l2c_shared_mask(int cpu)
 	return per_cpu(cpu_l2c_shared_map, cpu);
 }
 
-void acpi_setup_mp_wakeup_mailbox(u64 addr);
-struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void);
-u64 acpi_get_mp_wakeup_mailbox_paddr(void);
-
 #else /* !CONFIG_SMP */
 #define wbinvd_on_cpu(cpu)     wbinvd()
 static inline int wbinvd_on_all_cpus(void)

diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
@@ -239,6 +239,7 @@ extern bool x86_topology_update;
 
 #ifdef CONFIG_SCHED_MC_PRIO
 #include <asm/percpu.h>
+#include <linux/cache.h>
 
 DECLARE_PER_CPU_READ_MOSTLY(int, sched_core_priority);
 extern unsigned int __read_mostly sysctl_sched_itmt_enabled;

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
@@ -92,7 +92,6 @@ apm-y				:= apm_32.o
 obj-$(CONFIG_APM)		+= apm.o
 obj-$(CONFIG_SMP)		+= smp.o
 obj-$(CONFIG_SMP)		+= smpboot.o
-obj-$(CONFIG_X86_MAILBOX_WAKEUP) += smpwakeup.o
 obj-$(CONFIG_X86_TSC)		+= tsc_sync.o
 obj-$(CONFIG_SMP)		+= setup_percpu.o
 obj-$(CONFIG_X86_MPPARSE)	+= mpparse.o

diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
@@ -2,17 +2,25 @@
 #include <linux/acpi.h>
 #include <linux/cpu.h>
 #include <linux/delay.h>
+#include <linux/io.h>
 #include <linux/kexec.h>
 #include <linux/memblock.h>
 #include <linux/pgtable.h>
 #include <linux/sched/hotplug.h>
+#include <asm/apic.h>
 #include <asm/barrier.h>
 #include <asm/init.h>
 #include <asm/intel_pt.h>
 #include <asm/nmi.h>
 #include <asm/processor.h>
 #include <asm/reboot.h>
 
+/* Physical address of the Multiprocessor Wakeup Structure mailbox */
+static u64 acpi_mp_wake_mailbox_paddr __ro_after_init;
+
+/* Virtual address of the Multiprocessor Wakeup Structure mailbox */
+static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox;
+
 static u64 acpi_mp_pgd __ro_after_init;
 static u64 acpi_mp_reset_vector_paddr __ro_after_init;
 
@@ -29,7 +37,6 @@ static void acpi_mp_play_dead(void)
 
 static void acpi_mp_cpu_die(unsigned int cpu)
 {
-	struct acpi_madt_multiproc_wakeup_mailbox *mailbox = acpi_get_mp_wakeup_mailbox();
 	u32 apicid = per_cpu(x86_cpu_to_apicid, cpu);
 	unsigned long timeout;
 
@@ -39,13 +46,13 @@ static void acpi_mp_cpu_die(unsigned int cpu)
 	 *
 	 * BIOS has to clear 'command' field of the mailbox.
 	 */
-	mailbox->apic_id = apicid;
-	smp_store_release(&mailbox->command,
+	acpi_mp_wake_mailbox->apic_id = apicid;
+	smp_store_release(&acpi_mp_wake_mailbox->command,
 			  ACPI_MP_WAKE_COMMAND_TEST);
 
 	/* Don't wait longer than a second. */
 	timeout = USEC_PER_SEC;
-	while (READ_ONCE(mailbox->command) && --timeout)
+	while (READ_ONCE(acpi_mp_wake_mailbox->command) && --timeout)
 		udelay(1);
 
 	if (!timeout)
@@ -162,6 +169,63 @@ static int __init acpi_mp_setup_reset(u64 reset_vector)
 	return 0;
 }
 
+static int acpi_wakeup_cpu(u32 apicid, unsigned long start_ip, unsigned int cpu)
+{
+	if (!acpi_mp_wake_mailbox_paddr) {
+		pr_warn_once("No MADT mailbox: cannot bringup secondary CPUs. Booting with kexec?\n");
+		return -EOPNOTSUPP;
+	}
+
+	/*
+	 * Remap mailbox memory only for the first call to acpi_wakeup_cpu().
+	 *
+	 * Wakeup of secondary CPUs is fully serialized in the core code.
+	 * No need to protect acpi_mp_wake_mailbox from concurrent accesses.
+	 */
+	if (!acpi_mp_wake_mailbox) {
+		acpi_mp_wake_mailbox = memremap(acpi_mp_wake_mailbox_paddr,
+						sizeof(*acpi_mp_wake_mailbox),
+						MEMREMAP_WB);
+	}
+
+	/*
+	 * Mailbox memory is shared between the firmware and OS. Firmware will
+	 * listen on mailbox command address, and once it receives the wakeup
+	 * command, the CPU associated with the given apicid will be booted.
+	 *
+	 * The value of 'apic_id' and 'wakeup_vector' must be visible to the
+	 * firmware before the wakeup command is visible.  smp_store_release()
+	 * ensures ordering and visibility.
+	 */
+	acpi_mp_wake_mailbox->apic_id	    = apicid;
+	acpi_mp_wake_mailbox->wakeup_vector = start_ip;
+	smp_store_release(&acpi_mp_wake_mailbox->command,
+			  ACPI_MP_WAKE_COMMAND_WAKEUP);
+
+	/*
+	 * Wait for the CPU to wake up.
+	 *
+	 * The CPU being woken up is essentially in a spin loop waiting to be
+	 * woken up. It should not take long for it wake up and acknowledge by
+	 * zeroing out ->command.
+	 *
+	 * ACPI specification doesn't provide any guidance on how long kernel
+	 * has to wait for a wake up acknowledgment. It also doesn't provide
+	 * a way to cancel a wake up request if it takes too long.
+	 *
+	 * In TDX environment, the VMM has control over how long it takes to
+	 * wake up secondary. It can postpone scheduling secondary vCPU
+	 * indefinitely. Giving up on wake up request and reporting error opens
+	 * possible attack vector for VMM: it can wake up a secondary CPU when
+	 * kernel doesn't expect it. Wait until positive result of the wake up
+	 * request.
+	 */
+	while (READ_ONCE(acpi_mp_wake_mailbox->command))
+		cpu_relax();
+
+	return 0;
+}
+
 static void acpi_mp_disable_offlining(struct acpi_madt_multiproc_wakeup *mp_wake)
 {
 	cpu_hotplug_disable_offlining();
@@ -206,7 +270,7 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
 
 	acpi_table_print_madt_entry(&header->common);
 
-	acpi_setup_mp_wakeup_mailbox(mp_wake->mailbox_address);
+	acpi_mp_wake_mailbox_paddr = mp_wake->mailbox_address;
 
 	if (mp_wake->version >= ACPI_MADT_MP_WAKEUP_VERSION_V1 &&
 	    mp_wake->header.length >= ACPI_MADT_MP_WAKEUP_SIZE_V1) {
@@ -222,5 +286,23 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
 		acpi_mp_disable_offlining(mp_wake);
 	}
 
+	apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);
+
 	return 0;
 }
+
+void __init acpi_setup_mp_wakeup_mailbox(u64 mailbox_paddr)
+{
+	acpi_mp_wake_mailbox_paddr = mailbox_paddr;
+	apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);
+}
+
+struct acpi_madt_multiproc_wakeup_mailbox *acpi_get_mp_wakeup_mailbox(void)
+{
+	return acpi_mp_wake_mailbox;
+}
+
+u64 acpi_get_mp_wakeup_mailbox_paddr(void)
+{
+	return acpi_mp_wake_mailbox_paddr;
+}
diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
@@ -17,8 +17,8 @@
 #include <linux/pci.h>
 #include <linux/of_pci.h>
 #include <linux/initrd.h>
-#include <linux/smp.h>
 
+#include <asm/acpi.h>
 #include <asm/irqdomain.h>
 #include <asm/hpet.h>
 #include <asm/apic.h>