1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (c) 2023, Microsoft Corporation. 4 * 5 * Author: 6 * Saurabh Sengar <ssengar@microsoft.com> 7 */ 8 9 #include <asm/apic.h> 10 #include <asm/boot.h> 11 #include <asm/desc.h> 12 #include <asm/i8259.h> 13 #include <asm/mshyperv.h> 14 #include <asm/msr.h> 15 #include <asm/realmode.h> 16 #include <asm/reboot.h> 17 #include <../kernel/smpboot.h> 18 19 extern struct boot_params boot_params; 20 static struct real_mode_header hv_vtl_real_mode_header; 21 22 static bool __init hv_vtl_msi_ext_dest_id(void) 23 { 24 return true; 25 } 26 27 /* 28 * The `native_machine_emergency_restart` function from `reboot.c` writes 29 * to the physical address 0x472 to indicate the type of reboot for the 30 * firmware. We cannot have that in VSM as the memory composition might 31 * be more generic, and such write effectively corrupts the memory thus 32 * making diagnostics harder at the very least. 33 */ 34 static void __noreturn hv_vtl_emergency_restart(void) 35 { 36 /* 37 * Cause a triple fault and the immediate reset. Here the code does not run 38 * on the top of any firmware, whereby cannot reach out to its services. 39 * The inifinite loop is for the improbable case that the triple fault does 40 * not work and have to preserve the state intact for debugging. 41 */ 42 for (;;) { 43 idt_invalidate(); 44 __asm__ __volatile__("int3"); 45 } 46 } 47 48 /* 49 * The only way to restart in the VTL mode is to triple fault as the kernel runs 50 * as firmware. 51 */ 52 static void __noreturn hv_vtl_restart(char __maybe_unused *cmd) 53 { 54 hv_vtl_emergency_restart(); 55 } 56 57 void __init hv_vtl_init_platform(void) 58 { 59 /* 60 * This function is a no-op if the VTL mode is not enabled. 61 * If it is, this function runs if and only the kernel boots in 62 * VTL2 which the x86 hv initialization path makes sure of. 63 */ 64 pr_info("Linux runs in Hyper-V Virtual Trust Level %d\n", ms_hyperv.vtl); 65 66 x86_platform.realmode_reserve = x86_init_noop; 67 x86_platform.realmode_init = x86_init_noop; 68 x86_init.irqs.pre_vector_init = x86_init_noop; 69 x86_init.timers.timer_init = x86_init_noop; 70 x86_init.resources.probe_roms = x86_init_noop; 71 72 /* Avoid searching for BIOS MP tables */ 73 x86_init.mpparse.find_mptable = x86_init_noop; 74 x86_init.mpparse.early_parse_smp_cfg = x86_init_noop; 75 76 x86_platform.get_wallclock = get_rtc_noop; 77 x86_platform.set_wallclock = set_rtc_noop; 78 x86_platform.get_nmi_reason = hv_get_nmi_reason; 79 80 x86_platform.legacy.i8042 = X86_LEGACY_I8042_PLATFORM_ABSENT; 81 x86_platform.legacy.rtc = 0; 82 x86_platform.legacy.warm_reset = 0; 83 x86_platform.legacy.reserve_bios_regions = 0; 84 x86_platform.legacy.devices.pnpbios = 0; 85 86 x86_init.hyper.msi_ext_dest_id = hv_vtl_msi_ext_dest_id; 87 } 88 89 static inline u64 hv_vtl_system_desc_base(struct ldttss_desc *desc) 90 { 91 return ((u64)desc->base3 << 32) | ((u64)desc->base2 << 24) | 92 (desc->base1 << 16) | desc->base0; 93 } 94 95 static inline u32 hv_vtl_system_desc_limit(struct ldttss_desc *desc) 96 { 97 return ((u32)desc->limit1 << 16) | (u32)desc->limit0; 98 } 99 100 typedef void (*secondary_startup_64_fn)(void*, void*); 101 static void hv_vtl_ap_entry(void) 102 { 103 ((secondary_startup_64_fn)secondary_startup_64)(&boot_params, &boot_params); 104 } 105 106 static int hv_vtl_bringup_vcpu(u32 target_vp_index, int cpu, u64 eip_ignored) 107 { 108 u64 status; 109 int ret = 0; 110 struct hv_enable_vp_vtl *input; 111 unsigned long irq_flags; 112 113 struct desc_ptr gdt_ptr; 114 struct desc_ptr idt_ptr; 115 116 struct ldttss_desc *tss; 117 struct ldttss_desc *ldt; 118 struct desc_struct *gdt; 119 120 struct task_struct *idle = idle_thread_get(cpu); 121 u64 rsp = (unsigned long)idle->thread.sp; 122 123 u64 rip = (u64)&hv_vtl_ap_entry; 124 125 native_store_gdt(&gdt_ptr); 126 store_idt(&idt_ptr); 127 128 gdt = (struct desc_struct *)((void *)(gdt_ptr.address)); 129 tss = (struct ldttss_desc *)(gdt + GDT_ENTRY_TSS); 130 ldt = (struct ldttss_desc *)(gdt + GDT_ENTRY_LDT); 131 132 local_irq_save(irq_flags); 133 134 input = *this_cpu_ptr(hyperv_pcpu_input_arg); 135 memset(input, 0, sizeof(*input)); 136 137 input->partition_id = HV_PARTITION_ID_SELF; 138 input->vp_index = target_vp_index; 139 input->target_vtl.target_vtl = HV_VTL_MGMT; 140 141 /* 142 * The x86_64 Linux kernel follows the 16-bit -> 32-bit -> 64-bit 143 * mode transition sequence after waking up an AP with SIPI whose 144 * vector points to the 16-bit AP startup trampoline code. Here in 145 * VTL2, we can't perform that sequence as the AP has to start in 146 * the 64-bit mode. 147 * 148 * To make this happen, we tell the hypervisor to load a valid 64-bit 149 * context (most of which is just magic numbers from the CPU manual) 150 * so that AP jumps right to the 64-bit entry of the kernel, and the 151 * control registers are loaded with values that let the AP fetch the 152 * code and data and carry on with work it gets assigned. 153 */ 154 155 input->vp_context.rip = rip; 156 input->vp_context.rsp = rsp; 157 input->vp_context.rflags = 0x0000000000000002; 158 input->vp_context.efer = native_rdmsrq(MSR_EFER); 159 input->vp_context.cr0 = native_read_cr0(); 160 input->vp_context.cr3 = __native_read_cr3(); 161 input->vp_context.cr4 = native_read_cr4(); 162 input->vp_context.msr_cr_pat = native_rdmsrq(MSR_IA32_CR_PAT); 163 input->vp_context.idtr.limit = idt_ptr.size; 164 input->vp_context.idtr.base = idt_ptr.address; 165 input->vp_context.gdtr.limit = gdt_ptr.size; 166 input->vp_context.gdtr.base = gdt_ptr.address; 167 168 /* Non-system desc (64bit), long, code, present */ 169 input->vp_context.cs.selector = __KERNEL_CS; 170 input->vp_context.cs.base = 0; 171 input->vp_context.cs.limit = 0xffffffff; 172 input->vp_context.cs.attributes = 0xa09b; 173 /* Non-system desc (64bit), data, present, granularity, default */ 174 input->vp_context.ss.selector = __KERNEL_DS; 175 input->vp_context.ss.base = 0; 176 input->vp_context.ss.limit = 0xffffffff; 177 input->vp_context.ss.attributes = 0xc093; 178 179 /* System desc (128bit), present, LDT */ 180 input->vp_context.ldtr.selector = GDT_ENTRY_LDT * 8; 181 input->vp_context.ldtr.base = hv_vtl_system_desc_base(ldt); 182 input->vp_context.ldtr.limit = hv_vtl_system_desc_limit(ldt); 183 input->vp_context.ldtr.attributes = 0x82; 184 185 /* System desc (128bit), present, TSS, 0x8b - busy, 0x89 -- default */ 186 input->vp_context.tr.selector = GDT_ENTRY_TSS * 8; 187 input->vp_context.tr.base = hv_vtl_system_desc_base(tss); 188 input->vp_context.tr.limit = hv_vtl_system_desc_limit(tss); 189 input->vp_context.tr.attributes = 0x8b; 190 191 status = hv_do_hypercall(HVCALL_ENABLE_VP_VTL, input, NULL); 192 193 if (!hv_result_success(status) && 194 hv_result(status) != HV_STATUS_VTL_ALREADY_ENABLED) { 195 pr_err("HVCALL_ENABLE_VP_VTL failed for VP : %d ! [Err: %#llx\n]", 196 target_vp_index, status); 197 ret = -EINVAL; 198 goto free_lock; 199 } 200 201 status = hv_do_hypercall(HVCALL_START_VP, input, NULL); 202 203 if (!hv_result_success(status)) { 204 pr_err("HVCALL_START_VP failed for VP : %d ! [Err: %#llx]\n", 205 target_vp_index, status); 206 ret = -EINVAL; 207 } 208 209 free_lock: 210 local_irq_restore(irq_flags); 211 212 return ret; 213 } 214 215 static int hv_vtl_wakeup_secondary_cpu(u32 apicid, unsigned long start_eip, unsigned int cpu) 216 { 217 int vp_index; 218 219 pr_debug("Bringing up CPU with APIC ID %d in VTL2...\n", apicid); 220 vp_index = hv_apicid_to_vp_index(apicid); 221 222 if (vp_index < 0) { 223 pr_err("Couldn't find CPU with APIC ID %d\n", apicid); 224 return -EINVAL; 225 } 226 if (vp_index > ms_hyperv.max_vp_index) { 227 pr_err("Invalid CPU id %d for APIC ID %d\n", vp_index, apicid); 228 return -EINVAL; 229 } 230 231 return hv_vtl_bringup_vcpu(vp_index, cpu, start_eip); 232 } 233 234 int __init hv_vtl_early_init(void) 235 { 236 machine_ops.emergency_restart = hv_vtl_emergency_restart; 237 machine_ops.restart = hv_vtl_restart; 238 239 /* 240 * `boot_cpu_has` returns the runtime feature support, 241 * and here is the earliest it can be used. 242 */ 243 if (cpu_feature_enabled(X86_FEATURE_XSAVE)) 244 panic("XSAVE has to be disabled as it is not supported by this module.\n" 245 "Please add 'noxsave' to the kernel command line.\n"); 246 247 real_mode_header = &hv_vtl_real_mode_header; 248 apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu); 249 250 return 0; 251 } 252