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/realmode.h>
15#include <../kernel/smpboot.h>
16
17extern struct boot_params boot_params;
18static struct real_mode_header hv_vtl_real_mode_header;
19
20static bool __init hv_vtl_msi_ext_dest_id(void)
21{
22 return true;
23}
24
25void __init hv_vtl_init_platform(void)
26{
27 pr_info("Linux runs in Hyper-V Virtual Trust Level\n");
28
29 x86_platform.realmode_reserve = x86_init_noop;
30 x86_platform.realmode_init = x86_init_noop;
31 x86_init.irqs.pre_vector_init = x86_init_noop;
32 x86_init.timers.timer_init = x86_init_noop;
33
34 /* Avoid searching for BIOS MP tables */
35 x86_init.mpparse.find_mptable = x86_init_noop;
36 x86_init.mpparse.early_parse_smp_cfg = x86_init_noop;
37 x86_init.mpparse.parse_smp_cfg = x86_init_noop;
38
39 x86_platform.get_wallclock = get_rtc_noop;
40 x86_platform.set_wallclock = set_rtc_noop;
41 x86_platform.get_nmi_reason = hv_get_nmi_reason;
42
43 x86_platform.legacy.i8042 = X86_LEGACY_I8042_PLATFORM_ABSENT;
44 x86_platform.legacy.rtc = 0;
45 x86_platform.legacy.warm_reset = 0;
46 x86_platform.legacy.reserve_bios_regions = 0;
47 x86_platform.legacy.devices.pnpbios = 0;
48
49 x86_init.hyper.msi_ext_dest_id = hv_vtl_msi_ext_dest_id;
50}
51
52static inline u64 hv_vtl_system_desc_base(struct ldttss_desc *desc)
53{
54 return ((u64)desc->base3 << 32) | ((u64)desc->base2 << 24) |
55 (desc->base1 << 16) | desc->base0;
56}
57
58static inline u32 hv_vtl_system_desc_limit(struct ldttss_desc *desc)
59{
60 return ((u32)desc->limit1 << 16) | (u32)desc->limit0;
61}
62
63typedef void (*secondary_startup_64_fn)(void*, void*);
64static void hv_vtl_ap_entry(void)
65{
66 ((secondary_startup_64_fn)secondary_startup_64)(&boot_params, &boot_params);
67}
68
69static int hv_vtl_bringup_vcpu(u32 target_vp_index, int cpu, u64 eip_ignored)
70{
71 u64 status;
72 int ret = 0;
73 struct hv_enable_vp_vtl *input;
74 unsigned long irq_flags;
75
76 struct desc_ptr gdt_ptr;
77 struct desc_ptr idt_ptr;
78
79 struct ldttss_desc *tss;
80 struct ldttss_desc *ldt;
81 struct desc_struct *gdt;
82
83 struct task_struct *idle = idle_thread_get(cpu);
84 u64 rsp = (unsigned long)idle->thread.sp;
85
86 u64 rip = (u64)&hv_vtl_ap_entry;
87
88 native_store_gdt(dtr: &gdt_ptr);
89 store_idt(dtr: &idt_ptr);
90
91 gdt = (struct desc_struct *)((void *)(gdt_ptr.address));
92 tss = (struct ldttss_desc *)(gdt + GDT_ENTRY_TSS);
93 ldt = (struct ldttss_desc *)(gdt + GDT_ENTRY_LDT);
94
95 local_irq_save(irq_flags);
96
97 input = *this_cpu_ptr(hyperv_pcpu_input_arg);
98 memset(input, 0, sizeof(*input));
99
100 input->partition_id = HV_PARTITION_ID_SELF;
101 input->vp_index = target_vp_index;
102 input->target_vtl.target_vtl = HV_VTL_MGMT;
103
104 /*
105 * The x86_64 Linux kernel follows the 16-bit -> 32-bit -> 64-bit
106 * mode transition sequence after waking up an AP with SIPI whose
107 * vector points to the 16-bit AP startup trampoline code. Here in
108 * VTL2, we can't perform that sequence as the AP has to start in
109 * the 64-bit mode.
110 *
111 * To make this happen, we tell the hypervisor to load a valid 64-bit
112 * context (most of which is just magic numbers from the CPU manual)
113 * so that AP jumps right to the 64-bit entry of the kernel, and the
114 * control registers are loaded with values that let the AP fetch the
115 * code and data and carry on with work it gets assigned.
116 */
117
118 input->vp_context.rip = rip;
119 input->vp_context.rsp = rsp;
120 input->vp_context.rflags = 0x0000000000000002;
121 input->vp_context.efer = __rdmsr(MSR_EFER);
122 input->vp_context.cr0 = native_read_cr0();
123 input->vp_context.cr3 = __native_read_cr3();
124 input->vp_context.cr4 = native_read_cr4();
125 input->vp_context.msr_cr_pat = __rdmsr(MSR_IA32_CR_PAT);
126 input->vp_context.idtr.limit = idt_ptr.size;
127 input->vp_context.idtr.base = idt_ptr.address;
128 input->vp_context.gdtr.limit = gdt_ptr.size;
129 input->vp_context.gdtr.base = gdt_ptr.address;
130
131 /* Non-system desc (64bit), long, code, present */
132 input->vp_context.cs.selector = __KERNEL_CS;
133 input->vp_context.cs.base = 0;
134 input->vp_context.cs.limit = 0xffffffff;
135 input->vp_context.cs.attributes = 0xa09b;
136 /* Non-system desc (64bit), data, present, granularity, default */
137 input->vp_context.ss.selector = __KERNEL_DS;
138 input->vp_context.ss.base = 0;
139 input->vp_context.ss.limit = 0xffffffff;
140 input->vp_context.ss.attributes = 0xc093;
141
142 /* System desc (128bit), present, LDT */
143 input->vp_context.ldtr.selector = GDT_ENTRY_LDT * 8;
144 input->vp_context.ldtr.base = hv_vtl_system_desc_base(desc: ldt);
145 input->vp_context.ldtr.limit = hv_vtl_system_desc_limit(desc: ldt);
146 input->vp_context.ldtr.attributes = 0x82;
147
148 /* System desc (128bit), present, TSS, 0x8b - busy, 0x89 -- default */
149 input->vp_context.tr.selector = GDT_ENTRY_TSS * 8;
150 input->vp_context.tr.base = hv_vtl_system_desc_base(desc: tss);
151 input->vp_context.tr.limit = hv_vtl_system_desc_limit(desc: tss);
152 input->vp_context.tr.attributes = 0x8b;
153
154 status = hv_do_hypercall(HVCALL_ENABLE_VP_VTL, inputaddr: input, NULL);
155
156 if (!hv_result_success(status) &&
157 hv_result(status) != HV_STATUS_VTL_ALREADY_ENABLED) {
158 pr_err("HVCALL_ENABLE_VP_VTL failed for VP : %d ! [Err: %#llx\n]",
159 target_vp_index, status);
160 ret = -EINVAL;
161 goto free_lock;
162 }
163
164 status = hv_do_hypercall(HVCALL_START_VP, inputaddr: input, NULL);
165
166 if (!hv_result_success(status)) {
167 pr_err("HVCALL_START_VP failed for VP : %d ! [Err: %#llx]\n",
168 target_vp_index, status);
169 ret = -EINVAL;
170 }
171
172free_lock:
173 local_irq_restore(irq_flags);
174
175 return ret;
176}
177
178static int hv_vtl_apicid_to_vp_id(u32 apic_id)
179{
180 u64 control;
181 u64 status;
182 unsigned long irq_flags;
183 struct hv_get_vp_from_apic_id_in *input;
184 u32 *output, ret;
185
186 local_irq_save(irq_flags);
187
188 input = *this_cpu_ptr(hyperv_pcpu_input_arg);
189 memset(input, 0, sizeof(*input));
190 input->partition_id = HV_PARTITION_ID_SELF;
191 input->apic_ids[0] = apic_id;
192
193 output = (u32 *)input;
194
195 control = HV_HYPERCALL_REP_COMP_1 | HVCALL_GET_VP_ID_FROM_APIC_ID;
196 status = hv_do_hypercall(control, inputaddr: input, outputaddr: output);
197 ret = output[0];
198
199 local_irq_restore(irq_flags);
200
201 if (!hv_result_success(status)) {
202 pr_err("failed to get vp id from apic id %d, status %#llx\n",
203 apic_id, status);
204 return -EINVAL;
205 }
206
207 return ret;
208}
209
210static int hv_vtl_wakeup_secondary_cpu(u32 apicid, unsigned long start_eip)
211{
212 int vp_id, cpu;
213
214 /* Find the logical CPU for the APIC ID */
215 for_each_present_cpu(cpu) {
216 if (arch_match_cpu_phys_id(cpu, phys_id: apicid))
217 break;
218 }
219 if (cpu >= nr_cpu_ids)
220 return -EINVAL;
221
222 pr_debug("Bringing up CPU with APIC ID %d in VTL2...\n", apicid);
223 vp_id = hv_vtl_apicid_to_vp_id(apic_id: apicid);
224
225 if (vp_id < 0) {
226 pr_err("Couldn't find CPU with APIC ID %d\n", apicid);
227 return -EINVAL;
228 }
229 if (vp_id > ms_hyperv.max_vp_index) {
230 pr_err("Invalid CPU id %d for APIC ID %d\n", vp_id, apicid);
231 return -EINVAL;
232 }
233
234 return hv_vtl_bringup_vcpu(target_vp_index: vp_id, cpu, eip_ignored: start_eip);
235}
236
237int __init hv_vtl_early_init(void)
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(fmt: "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

source code of linux/arch/x86/hyperv/hv_vtl.c