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 pr_info("Linux runs in Hyper-V Virtual Trust Level\n"); 60 61 x86_platform.realmode_reserve = x86_init_noop; 62 x86_platform.realmode_init = x86_init_noop; 63 x86_init.irqs.pre_vector_init = x86_init_noop; 64 x86_init.timers.timer_init = x86_init_noop; 65 x86_init.resources.probe_roms = x86_init_noop; 66 67 /* Avoid searching for BIOS MP tables */ 68 x86_init.mpparse.find_mptable = x86_init_noop; 69 x86_init.mpparse.early_parse_smp_cfg = x86_init_noop; 70 71 x86_platform.get_wallclock = get_rtc_noop; 72 x86_platform.set_wallclock = set_rtc_noop; 73 x86_platform.get_nmi_reason = hv_get_nmi_reason; 74 75 x86_platform.legacy.i8042 = X86_LEGACY_I8042_PLATFORM_ABSENT; 76 x86_platform.legacy.rtc = 0; 77 x86_platform.legacy.warm_reset = 0; 78 x86_platform.legacy.reserve_bios_regions = 0; 79 x86_platform.legacy.devices.pnpbios = 0; 80 81 x86_init.hyper.msi_ext_dest_id = hv_vtl_msi_ext_dest_id; 82 } 83 84 static inline u64 hv_vtl_system_desc_base(struct ldttss_desc *desc) 85 { 86 return ((u64)desc->base3 << 32) | ((u64)desc->base2 << 24) | 87 (desc->base1 << 16) | desc->base0; 88 } 89 90 static inline u32 hv_vtl_system_desc_limit(struct ldttss_desc *desc) 91 { 92 return ((u32)desc->limit1 << 16) | (u32)desc->limit0; 93 } 94 95 typedef void (*secondary_startup_64_fn)(void*, void*); 96 static void hv_vtl_ap_entry(void) 97 { 98 ((secondary_startup_64_fn)secondary_startup_64)(&boot_params, &boot_params); 99 } 100 101 static int hv_vtl_bringup_vcpu(u32 target_vp_index, int cpu, u64 eip_ignored) 102 { 103 u64 status; 104 int ret = 0; 105 struct hv_enable_vp_vtl *input; 106 unsigned long irq_flags; 107 108 struct desc_ptr gdt_ptr; 109 struct desc_ptr idt_ptr; 110 111 struct ldttss_desc *tss; 112 struct ldttss_desc *ldt; 113 struct desc_struct *gdt; 114 115 struct task_struct *idle = idle_thread_get(cpu); 116 u64 rsp = (unsigned long)idle->thread.sp; 117 118 u64 rip = (u64)&hv_vtl_ap_entry; 119 120 native_store_gdt(&gdt_ptr); 121 store_idt(&idt_ptr); 122 123 gdt = (struct desc_struct *)((void *)(gdt_ptr.address)); 124 tss = (struct ldttss_desc *)(gdt + GDT_ENTRY_TSS); 125 ldt = (struct ldttss_desc *)(gdt + GDT_ENTRY_LDT); 126 127 local_irq_save(irq_flags); 128 129 input = *this_cpu_ptr(hyperv_pcpu_input_arg); 130 memset(input, 0, sizeof(*input)); 131 132 input->partition_id = HV_PARTITION_ID_SELF; 133 input->vp_index = target_vp_index; 134 input->target_vtl.target_vtl = HV_VTL_MGMT; 135 136 /* 137 * The x86_64 Linux kernel follows the 16-bit -> 32-bit -> 64-bit 138 * mode transition sequence after waking up an AP with SIPI whose 139 * vector points to the 16-bit AP startup trampoline code. Here in 140 * VTL2, we can't perform that sequence as the AP has to start in 141 * the 64-bit mode. 142 * 143 * To make this happen, we tell the hypervisor to load a valid 64-bit 144 * context (most of which is just magic numbers from the CPU manual) 145 * so that AP jumps right to the 64-bit entry of the kernel, and the 146 * control registers are loaded with values that let the AP fetch the 147 * code and data and carry on with work it gets assigned. 148 */ 149 150 input->vp_context.rip = rip; 151 input->vp_context.rsp = rsp; 152 input->vp_context.rflags = 0x0000000000000002; 153 input->vp_context.efer = native_rdmsrq(MSR_EFER); 154 input->vp_context.cr0 = native_read_cr0(); 155 input->vp_context.cr3 = __native_read_cr3(); 156 input->vp_context.cr4 = native_read_cr4(); 157 input->vp_context.msr_cr_pat = native_rdmsrq(MSR_IA32_CR_PAT); 158 input->vp_context.idtr.limit = idt_ptr.size; 159 input->vp_context.idtr.base = idt_ptr.address; 160 input->vp_context.gdtr.limit = gdt_ptr.size; 161 input->vp_context.gdtr.base = gdt_ptr.address; 162 163 /* Non-system desc (64bit), long, code, present */ 164 input->vp_context.cs.selector = __KERNEL_CS; 165 input->vp_context.cs.base = 0; 166 input->vp_context.cs.limit = 0xffffffff; 167 input->vp_context.cs.attributes = 0xa09b; 168 /* Non-system desc (64bit), data, present, granularity, default */ 169 input->vp_context.ss.selector = __KERNEL_DS; 170 input->vp_context.ss.base = 0; 171 input->vp_context.ss.limit = 0xffffffff; 172 input->vp_context.ss.attributes = 0xc093; 173 174 /* System desc (128bit), present, LDT */ 175 input->vp_context.ldtr.selector = GDT_ENTRY_LDT * 8; 176 input->vp_context.ldtr.base = hv_vtl_system_desc_base(ldt); 177 input->vp_context.ldtr.limit = hv_vtl_system_desc_limit(ldt); 178 input->vp_context.ldtr.attributes = 0x82; 179 180 /* System desc (128bit), present, TSS, 0x8b - busy, 0x89 -- default */ 181 input->vp_context.tr.selector = GDT_ENTRY_TSS * 8; 182 input->vp_context.tr.base = hv_vtl_system_desc_base(tss); 183 input->vp_context.tr.limit = hv_vtl_system_desc_limit(tss); 184 input->vp_context.tr.attributes = 0x8b; 185 186 status = hv_do_hypercall(HVCALL_ENABLE_VP_VTL, input, NULL); 187 188 if (!hv_result_success(status) && 189 hv_result(status) != HV_STATUS_VTL_ALREADY_ENABLED) { 190 pr_err("HVCALL_ENABLE_VP_VTL failed for VP : %d ! [Err: %#llx\n]", 191 target_vp_index, status); 192 ret = -EINVAL; 193 goto free_lock; 194 } 195 196 status = hv_do_hypercall(HVCALL_START_VP, input, NULL); 197 198 if (!hv_result_success(status)) { 199 pr_err("HVCALL_START_VP failed for VP : %d ! [Err: %#llx]\n", 200 target_vp_index, status); 201 ret = -EINVAL; 202 } 203 204 free_lock: 205 local_irq_restore(irq_flags); 206 207 return ret; 208 } 209 210 static int hv_vtl_apicid_to_vp_id(u32 apic_id) 211 { 212 u64 control; 213 u64 status; 214 unsigned long irq_flags; 215 struct hv_get_vp_from_apic_id_in *input; 216 u32 *output, ret; 217 218 local_irq_save(irq_flags); 219 220 input = *this_cpu_ptr(hyperv_pcpu_input_arg); 221 memset(input, 0, sizeof(*input)); 222 input->partition_id = HV_PARTITION_ID_SELF; 223 input->apic_ids[0] = apic_id; 224 225 output = *this_cpu_ptr(hyperv_pcpu_output_arg); 226 227 control = HV_HYPERCALL_REP_COMP_1 | HVCALL_GET_VP_ID_FROM_APIC_ID; 228 status = hv_do_hypercall(control, input, output); 229 ret = output[0]; 230 231 local_irq_restore(irq_flags); 232 233 if (!hv_result_success(status)) { 234 pr_err("failed to get vp id from apic id %d, status %#llx\n", 235 apic_id, status); 236 return -EINVAL; 237 } 238 239 return ret; 240 } 241 242 static int hv_vtl_wakeup_secondary_cpu(u32 apicid, unsigned long start_eip) 243 { 244 int vp_id, cpu; 245 246 /* Find the logical CPU for the APIC ID */ 247 for_each_present_cpu(cpu) { 248 if (arch_match_cpu_phys_id(cpu, apicid)) 249 break; 250 } 251 if (cpu >= nr_cpu_ids) 252 return -EINVAL; 253 254 pr_debug("Bringing up CPU with APIC ID %d in VTL2...\n", apicid); 255 vp_id = hv_vtl_apicid_to_vp_id(apicid); 256 257 if (vp_id < 0) { 258 pr_err("Couldn't find CPU with APIC ID %d\n", apicid); 259 return -EINVAL; 260 } 261 if (vp_id > ms_hyperv.max_vp_index) { 262 pr_err("Invalid CPU id %d for APIC ID %d\n", vp_id, apicid); 263 return -EINVAL; 264 } 265 266 return hv_vtl_bringup_vcpu(vp_id, cpu, start_eip); 267 } 268 269 int __init hv_vtl_early_init(void) 270 { 271 machine_ops.emergency_restart = hv_vtl_emergency_restart; 272 machine_ops.restart = hv_vtl_restart; 273 274 /* 275 * `boot_cpu_has` returns the runtime feature support, 276 * and here is the earliest it can be used. 277 */ 278 if (cpu_feature_enabled(X86_FEATURE_XSAVE)) 279 panic("XSAVE has to be disabled as it is not supported by this module.\n" 280 "Please add 'noxsave' to the kernel command line.\n"); 281 282 real_mode_header = &hv_vtl_real_mode_header; 283 apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu); 284 285 return 0; 286 } 287