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
16extern struct boot_params boot_params;
17static struct real_mode_header hv_vtl_real_mode_header;
18
19void __init hv_vtl_init_platform(void)
20{
21 pr_info("Linux runs in Hyper-V Virtual Trust Level\n");
22
23 x86_platform.realmode_reserve = x86_init_noop;
24 x86_platform.realmode_init = x86_init_noop;
25 x86_init.irqs.pre_vector_init = x86_init_noop;
26 x86_init.timers.timer_init = x86_init_noop;
27
28 /* Avoid searching for BIOS MP tables */
29 x86_init.mpparse.find_smp_config = x86_init_noop;
30 x86_init.mpparse.get_smp_config = x86_init_uint_noop;
31
32 x86_platform.get_wallclock = get_rtc_noop;
33 x86_platform.set_wallclock = set_rtc_noop;
34 x86_platform.get_nmi_reason = hv_get_nmi_reason;
35
36 x86_platform.legacy.i8042 = X86_LEGACY_I8042_PLATFORM_ABSENT;
37 x86_platform.legacy.rtc = 0;
38 x86_platform.legacy.warm_reset = 0;
39 x86_platform.legacy.reserve_bios_regions = 0;
40 x86_platform.legacy.devices.pnpbios = 0;
41}
42
43static inline u64 hv_vtl_system_desc_base(struct ldttss_desc *desc)
44{
45 return ((u64)desc->base3 << 32) | ((u64)desc->base2 << 24) |
46 (desc->base1 << 16) | desc->base0;
47}
48
49static inline u32 hv_vtl_system_desc_limit(struct ldttss_desc *desc)
50{
51 return ((u32)desc->limit1 << 16) | (u32)desc->limit0;
52}
53
54typedef void (*secondary_startup_64_fn)(void*, void*);
55static void hv_vtl_ap_entry(void)
56{
57 ((secondary_startup_64_fn)secondary_startup_64)(&boot_params, &boot_params);
58}
59
60static int hv_vtl_bringup_vcpu(u32 target_vp_index, u64 eip_ignored)
61{
62 u64 status;
63 int ret = 0;
64 struct hv_enable_vp_vtl *input;
65 unsigned long irq_flags;
66
67 struct desc_ptr gdt_ptr;
68 struct desc_ptr idt_ptr;
69
70 struct ldttss_desc *tss;
71 struct ldttss_desc *ldt;
72 struct desc_struct *gdt;
73
74 u64 rsp = current->thread.sp;
75 u64 rip = (u64)&hv_vtl_ap_entry;
76
77 native_store_gdt(dtr: &gdt_ptr);
78 store_idt(dtr: &idt_ptr);
79
80 gdt = (struct desc_struct *)((void *)(gdt_ptr.address));
81 tss = (struct ldttss_desc *)(gdt + GDT_ENTRY_TSS);
82 ldt = (struct ldttss_desc *)(gdt + GDT_ENTRY_LDT);
83
84 local_irq_save(irq_flags);
85
86 input = *this_cpu_ptr(hyperv_pcpu_input_arg);
87 memset(input, 0, sizeof(*input));
88
89 input->partition_id = HV_PARTITION_ID_SELF;
90 input->vp_index = target_vp_index;
91 input->target_vtl.target_vtl = HV_VTL_MGMT;
92
93 /*
94 * The x86_64 Linux kernel follows the 16-bit -> 32-bit -> 64-bit
95 * mode transition sequence after waking up an AP with SIPI whose
96 * vector points to the 16-bit AP startup trampoline code. Here in
97 * VTL2, we can't perform that sequence as the AP has to start in
98 * the 64-bit mode.
99 *
100 * To make this happen, we tell the hypervisor to load a valid 64-bit
101 * context (most of which is just magic numbers from the CPU manual)
102 * so that AP jumps right to the 64-bit entry of the kernel, and the
103 * control registers are loaded with values that let the AP fetch the
104 * code and data and carry on with work it gets assigned.
105 */
106
107 input->vp_context.rip = rip;
108 input->vp_context.rsp = rsp;
109 input->vp_context.rflags = 0x0000000000000002;
110 input->vp_context.efer = __rdmsr(MSR_EFER);
111 input->vp_context.cr0 = native_read_cr0();
112 input->vp_context.cr3 = __native_read_cr3();
113 input->vp_context.cr4 = native_read_cr4();
114 input->vp_context.msr_cr_pat = __rdmsr(MSR_IA32_CR_PAT);
115 input->vp_context.idtr.limit = idt_ptr.size;
116 input->vp_context.idtr.base = idt_ptr.address;
117 input->vp_context.gdtr.limit = gdt_ptr.size;
118 input->vp_context.gdtr.base = gdt_ptr.address;
119
120 /* Non-system desc (64bit), long, code, present */
121 input->vp_context.cs.selector = __KERNEL_CS;
122 input->vp_context.cs.base = 0;
123 input->vp_context.cs.limit = 0xffffffff;
124 input->vp_context.cs.attributes = 0xa09b;
125 /* Non-system desc (64bit), data, present, granularity, default */
126 input->vp_context.ss.selector = __KERNEL_DS;
127 input->vp_context.ss.base = 0;
128 input->vp_context.ss.limit = 0xffffffff;
129 input->vp_context.ss.attributes = 0xc093;
130
131 /* System desc (128bit), present, LDT */
132 input->vp_context.ldtr.selector = GDT_ENTRY_LDT * 8;
133 input->vp_context.ldtr.base = hv_vtl_system_desc_base(desc: ldt);
134 input->vp_context.ldtr.limit = hv_vtl_system_desc_limit(desc: ldt);
135 input->vp_context.ldtr.attributes = 0x82;
136
137 /* System desc (128bit), present, TSS, 0x8b - busy, 0x89 -- default */
138 input->vp_context.tr.selector = GDT_ENTRY_TSS * 8;
139 input->vp_context.tr.base = hv_vtl_system_desc_base(desc: tss);
140 input->vp_context.tr.limit = hv_vtl_system_desc_limit(desc: tss);
141 input->vp_context.tr.attributes = 0x8b;
142
143 status = hv_do_hypercall(HVCALL_ENABLE_VP_VTL, inputaddr: input, NULL);
144
145 if (!hv_result_success(status) &&
146 hv_result(status) != HV_STATUS_VTL_ALREADY_ENABLED) {
147 pr_err("HVCALL_ENABLE_VP_VTL failed for VP : %d ! [Err: %#llx\n]",
148 target_vp_index, status);
149 ret = -EINVAL;
150 goto free_lock;
151 }
152
153 status = hv_do_hypercall(HVCALL_START_VP, inputaddr: input, NULL);
154
155 if (!hv_result_success(status)) {
156 pr_err("HVCALL_START_VP failed for VP : %d ! [Err: %#llx]\n",
157 target_vp_index, status);
158 ret = -EINVAL;
159 }
160
161free_lock:
162 local_irq_restore(irq_flags);
163
164 return ret;
165}
166
167static int hv_vtl_apicid_to_vp_id(u32 apic_id)
168{
169 u64 control;
170 u64 status;
171 unsigned long irq_flags;
172 struct hv_get_vp_from_apic_id_in *input;
173 u32 *output, ret;
174
175 local_irq_save(irq_flags);
176
177 input = *this_cpu_ptr(hyperv_pcpu_input_arg);
178 memset(input, 0, sizeof(*input));
179 input->partition_id = HV_PARTITION_ID_SELF;
180 input->apic_ids[0] = apic_id;
181
182 output = (u32 *)input;
183
184 control = HV_HYPERCALL_REP_COMP_1 | HVCALL_GET_VP_ID_FROM_APIC_ID;
185 status = hv_do_hypercall(control, inputaddr: input, outputaddr: output);
186 ret = output[0];
187
188 local_irq_restore(irq_flags);
189
190 if (!hv_result_success(status)) {
191 pr_err("failed to get vp id from apic id %d, status %#llx\n",
192 apic_id, status);
193 return -EINVAL;
194 }
195
196 return ret;
197}
198
199static int hv_vtl_wakeup_secondary_cpu(u32 apicid, unsigned long start_eip)
200{
201 int vp_id;
202
203 pr_debug("Bringing up CPU with APIC ID %d in VTL2...\n", apicid);
204 vp_id = hv_vtl_apicid_to_vp_id(apic_id: apicid);
205
206 if (vp_id < 0) {
207 pr_err("Couldn't find CPU with APIC ID %d\n", apicid);
208 return -EINVAL;
209 }
210 if (vp_id > ms_hyperv.max_vp_index) {
211 pr_err("Invalid CPU id %d for APIC ID %d\n", vp_id, apicid);
212 return -EINVAL;
213 }
214
215 return hv_vtl_bringup_vcpu(target_vp_index: vp_id, eip_ignored: start_eip);
216}
217
218int __init hv_vtl_early_init(void)
219{
220 /*
221 * `boot_cpu_has` returns the runtime feature support,
222 * and here is the earliest it can be used.
223 */
224 if (cpu_feature_enabled(X86_FEATURE_XSAVE))
225 panic(fmt: "XSAVE has to be disabled as it is not supported by this module.\n"
226 "Please add 'noxsave' to the kernel command line.\n");
227
228 real_mode_header = &hv_vtl_real_mode_header;
229 apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu);
230
231 return 0;
232}
233

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