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(&gdt_ptr);
89	store_idt(&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(ldt);
145	input->vp_context.ldtr.limit = hv_vtl_system_desc_limit(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(tss);
151	input->vp_context.tr.limit = hv_vtl_system_desc_limit(tss);
152	input->vp_context.tr.attributes = 0x8b;
153
154	status = hv_do_hypercall(HVCALL_ENABLE_VP_VTL, 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, 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, input, 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, 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(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(vp_id, cpu, 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("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