1 // SPDX-License-Identifier: GPL-2.0
2
3 /*
4 * Low level utility routines for interacting with Hyper-V.
5 *
6 * Copyright (C) 2021, Microsoft, Inc.
7 *
8 * Author : Michael Kelley <mikelley@microsoft.com>
9 */
10
11 #include <linux/types.h>
12 #include <linux/export.h>
13 #include <linux/mm.h>
14 #include <linux/hyperv.h>
15 #include <linux/arm-smccc.h>
16 #include <linux/module.h>
17 #include <asm-generic/bug.h>
18 #include <asm/hyperv-tlfs.h>
19 #include <asm/mshyperv.h>
20
21 /*
22 * hv_do_hypercall- Invoke the specified hypercall
23 */
24 u64 hv_do_hypercall(u64 control, void *input, void *output)
25 {
26 struct arm_smccc_res res;
27 u64 input_address;
28 u64 output_address;
29
30 input_address = input ? virt_to_phys(input) : 0;
31 output_address = output ? virt_to_phys(output) : 0;
32
33 arm_smccc_1_1_hvc(HV_FUNC_ID, control,
34 input_address, output_address, &res);
35 return res.a0;
36 }
37 EXPORT_SYMBOL_GPL(hv_do_hypercall);
38
39 /*
40 * hv_do_fast_hypercall8 -- Invoke the specified hypercall
41 * with arguments in registers instead of physical memory.
42 * Avoids the overhead of virt_to_phys for simple hypercalls.
43 */
44
45 u64 hv_do_fast_hypercall8(u16 code, u64 input)
46 {
47 struct arm_smccc_res res;
48 u64 control;
49
50 control = (u64)code | HV_HYPERCALL_FAST_BIT;
51
52 arm_smccc_1_1_hvc(HV_FUNC_ID, control, input, &res);
53 return res.a0;
54 }
55 EXPORT_SYMBOL_GPL(hv_do_fast_hypercall8);
56
57 /*
58 * Set a single VP register to a 64-bit value.
59 */
60 void hv_set_vpreg(u32 msr, u64 value)
61 {
62 struct arm_smccc_res res;
63
64 arm_smccc_1_1_hvc(HV_FUNC_ID,
65 HVCALL_SET_VP_REGISTERS | HV_HYPERCALL_FAST_BIT |
66 HV_HYPERCALL_REP_COMP_1,
67 HV_PARTITION_ID_SELF,
68 HV_VP_INDEX_SELF,
69 msr,
70 0,
71 value,
72 0,
73 &res);
74
75 /*
76 * Something is fundamentally broken in the hypervisor if
77 * setting a VP register fails. There's really no way to
78 * continue as a guest VM, so panic.
79 */
80 BUG_ON(!hv_result_success(res.a0));
81 }
82 EXPORT_SYMBOL_GPL(hv_set_vpreg);
83
84 /*
85 * Get the value of a single VP register. One version
86 * returns just 64 bits and another returns the full 128 bits.
87 * The two versions are separate to avoid complicating the
88 * calling sequence for the more frequently used 64 bit version.
89 */
90
91 void hv_get_vpreg_128(u32 msr, struct hv_get_vp_registers_output *result)
92 {
93 struct arm_smccc_1_2_regs args;
94 struct arm_smccc_1_2_regs res;
95
96 args.a0 = HV_FUNC_ID;
97 args.a1 = HVCALL_GET_VP_REGISTERS | HV_HYPERCALL_FAST_BIT |
98 HV_HYPERCALL_REP_COMP_1;
99 args.a2 = HV_PARTITION_ID_SELF;
100 args.a3 = HV_VP_INDEX_SELF;
101 args.a4 = msr;
102
103 /*
104 * Use the SMCCC 1.2 interface because the results are in registers
105 * beyond X0-X3.
106 */
107 arm_smccc_1_2_hvc(&args, &res);
108
109 /*
110 * Something is fundamentally broken in the hypervisor if
111 * getting a VP register fails. There's really no way to
112 * continue as a guest VM, so panic.
113 */
114 BUG_ON(!hv_result_success(res.a0));
115
116 result->as64.low = res.a6;
117 result->as64.high = res.a7;
118 }
119 EXPORT_SYMBOL_GPL(hv_get_vpreg_128);
120
121 u64 hv_get_vpreg(u32 msr)
122 {
123 struct hv_get_vp_registers_output output;
124
125 hv_get_vpreg_128(msr, &output);
126
127 return output.as64.low;
128 }
129 EXPORT_SYMBOL_GPL(hv_get_vpreg);
130
131 /*
132 * hyperv_report_panic - report a panic to Hyper-V. This function uses
133 * the older version of the Hyper-V interface that admittedly doesn't
134 * pass enough information to be useful beyond just recording the
135 * occurrence of a panic. The parallel hv_kmsg_dump() uses the
136 * new interface that allows reporting 4 Kbytes of data, which is much
137 * more useful. Hyper-V on ARM64 always supports the newer interface, but
138 * we retain support for the older version because the sysadmin is allowed
139 * to disable the newer version via sysctl in case of information security
140 * concerns about the more verbose version.
141 */
142 void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die)
143 {
144 static bool panic_reported;
145 u64 guest_id;
146
147 /* Don't report a panic to Hyper-V if we're not going to panic */
148 if (in_die && !panic_on_oops)
149 return;
150
151 /*
152 * We prefer to report panic on 'die' chain as we have proper
153 * registers to report, but if we miss it (e.g. on BUG()) we need
154 * to report it on 'panic'.
155 *
156 * Calling code in the 'die' and 'panic' paths ensures that only
157 * one CPU is running this code, so no atomicity is needed.
158 */
159 if (panic_reported)
160 return;
161 panic_reported = true;
162
163 guest_id = hv_get_vpreg(HV_REGISTER_GUEST_OS_ID);
164
165 /*
166 * Hyper-V provides the ability to store only 5 values.
167 * Pick the passed in error value, the guest_id, the PC,
168 * and the SP.
169 */
170 hv_set_vpreg(HV_REGISTER_GUEST_CRASH_P0, err);
171 hv_set_vpreg(HV_REGISTER_GUEST_CRASH_P1, guest_id);
172 hv_set_vpreg(HV_REGISTER_GUEST_CRASH_P2, regs->pc);
173 hv_set_vpreg(HV_REGISTER_GUEST_CRASH_P3, regs->sp);
174 hv_set_vpreg(HV_REGISTER_GUEST_CRASH_P4, 0);
175
176 /*
177 * Let Hyper-V know there is crash data available
178 */
179 hv_set_vpreg(HV_REGISTER_GUEST_CRASH_CTL, HV_CRASH_CTL_CRASH_NOTIFY);
180 }
181 EXPORT_SYMBOL_GPL(hyperv_report_panic);
182
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