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/arm-smccc.h>
15#include <linux/module.h>
16#include <asm-generic/bug.h>
17#include <hyperv/hvhdk.h>
18#include <asm/mshyperv.h>
19
20/*
21 * hv_do_hypercall- Invoke the specified hypercall
22 */
23u64 hv_do_hypercall(u64 control, void *input, void *output)
24{
25 struct arm_smccc_res res;
26 u64 input_address;
27 u64 output_address;
28
29 input_address = input ? virt_to_phys(address: input) : 0;
30 output_address = output ? virt_to_phys(address: output) : 0;
31
32 arm_smccc_1_1_hvc(HV_FUNC_ID, control,
33 input_address, output_address, &res);
34 return res.a0;
35}
36EXPORT_SYMBOL_GPL(hv_do_hypercall);
37
38/*
39 * hv_do_fast_hypercall8 -- Invoke the specified hypercall
40 * with arguments in registers instead of physical memory.
41 * Avoids the overhead of virt_to_phys for simple hypercalls.
42 */
43
44u64 hv_do_fast_hypercall8(u16 code, u64 input)
45{
46 struct arm_smccc_res res;
47 u64 control;
48
49 control = (u64)code | HV_HYPERCALL_FAST_BIT;
50
51 arm_smccc_1_1_hvc(HV_FUNC_ID, control, input, &res);
52 return res.a0;
53}
54EXPORT_SYMBOL_GPL(hv_do_fast_hypercall8);
55
56/*
57 * hv_do_fast_hypercall16 -- Invoke the specified hypercall
58 * with arguments in registers instead of physical memory.
59 * Avoids the overhead of virt_to_phys for simple hypercalls.
60 */
61u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input2)
62{
63 struct arm_smccc_res res;
64 u64 control;
65
66 control = (u64)code | HV_HYPERCALL_FAST_BIT;
67
68 arm_smccc_1_1_hvc(HV_FUNC_ID, control, input1, input2, &res);
69 return res.a0;
70}
71EXPORT_SYMBOL_GPL(hv_do_fast_hypercall16);
72
73/*
74 * Set a single VP register to a 64-bit value.
75 */
76void hv_set_vpreg(u32 msr, u64 value)
77{
78 struct arm_smccc_res res;
79
80 arm_smccc_1_1_hvc(HV_FUNC_ID,
81 HVCALL_SET_VP_REGISTERS | HV_HYPERCALL_FAST_BIT |
82 HV_HYPERCALL_REP_COMP_1,
83 HV_PARTITION_ID_SELF,
84 HV_VP_INDEX_SELF,
85 msr,
86 0,
87 value,
88 0,
89 &res);
90
91 /*
92 * Something is fundamentally broken in the hypervisor if
93 * setting a VP register fails. There's really no way to
94 * continue as a guest VM, so panic.
95 */
96 BUG_ON(!hv_result_success(res.a0));
97}
98EXPORT_SYMBOL_GPL(hv_set_vpreg);
99
100/*
101 * Get the value of a single VP register. One version
102 * returns just 64 bits and another returns the full 128 bits.
103 * The two versions are separate to avoid complicating the
104 * calling sequence for the more frequently used 64 bit version.
105 */
106
107void hv_get_vpreg_128(u32 msr, struct hv_get_vp_registers_output *result)
108{
109 struct arm_smccc_1_2_regs args;
110 struct arm_smccc_1_2_regs res;
111
112 args.a0 = HV_FUNC_ID;
113 args.a1 = HVCALL_GET_VP_REGISTERS | HV_HYPERCALL_FAST_BIT |
114 HV_HYPERCALL_REP_COMP_1;
115 args.a2 = HV_PARTITION_ID_SELF;
116 args.a3 = HV_VP_INDEX_SELF;
117 args.a4 = msr;
118
119 /*
120 * Use the SMCCC 1.2 interface because the results are in registers
121 * beyond X0-X3.
122 */
123 arm_smccc_1_2_hvc(&args, &res);
124
125 /*
126 * Something is fundamentally broken in the hypervisor if
127 * getting a VP register fails. There's really no way to
128 * continue as a guest VM, so panic.
129 */
130 BUG_ON(!hv_result_success(res.a0));
131
132 result->as64.low = res.a6;
133 result->as64.high = res.a7;
134}
135EXPORT_SYMBOL_GPL(hv_get_vpreg_128);
136
137u64 hv_get_vpreg(u32 msr)
138{
139 struct hv_get_vp_registers_output output;
140
141 hv_get_vpreg_128(msr, &output);
142
143 return output.as64.low;
144}
145EXPORT_SYMBOL_GPL(hv_get_vpreg);
146
147/*
148 * hyperv_report_panic - report a panic to Hyper-V. This function uses
149 * the older version of the Hyper-V interface that admittedly doesn't
150 * pass enough information to be useful beyond just recording the
151 * occurrence of a panic. The parallel hv_kmsg_dump() uses the
152 * new interface that allows reporting 4 Kbytes of data, which is much
153 * more useful. Hyper-V on ARM64 always supports the newer interface, but
154 * we retain support for the older version because the sysadmin is allowed
155 * to disable the newer version via sysctl in case of information security
156 * concerns about the more verbose version.
157 */
158void hyperv_report_panic(struct pt_regs *regs, long err, bool in_die)
159{
160 static bool panic_reported;
161 u64 guest_id;
162
163 /* Don't report a panic to Hyper-V if we're not going to panic */
164 if (in_die && !panic_on_oops)
165 return;
166
167 /*
168 * We prefer to report panic on 'die' chain as we have proper
169 * registers to report, but if we miss it (e.g. on BUG()) we need
170 * to report it on 'panic'.
171 *
172 * Calling code in the 'die' and 'panic' paths ensures that only
173 * one CPU is running this code, so no atomicity is needed.
174 */
175 if (panic_reported)
176 return;
177 panic_reported = true;
178
179 guest_id = hv_get_vpreg(HV_REGISTER_GUEST_OS_ID);
180
181 /*
182 * Hyper-V provides the ability to store only 5 values.
183 * Pick the passed in error value, the guest_id, the PC,
184 * and the SP.
185 */
186 hv_set_vpreg(HV_REGISTER_GUEST_CRASH_P0, err);
187 hv_set_vpreg(HV_REGISTER_GUEST_CRASH_P1, guest_id);
188 hv_set_vpreg(HV_REGISTER_GUEST_CRASH_P2, regs->pc);
189 hv_set_vpreg(HV_REGISTER_GUEST_CRASH_P3, regs->sp);
190 hv_set_vpreg(HV_REGISTER_GUEST_CRASH_P4, 0);
191
192 /*
193 * Let Hyper-V know there is crash data available
194 */
195 hv_set_vpreg(HV_REGISTER_GUEST_CRASH_CTL, HV_CRASH_CTL_CRASH_NOTIFY);
196}
197EXPORT_SYMBOL_GPL(hyperv_report_panic);
198

source code of linux/arch/arm64/hyperv/hv_core.c