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  */
hv_do_hypercall(u64 control,void * input,void * output)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 
hv_do_fast_hypercall8(u16 code,u64 input)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  */
hv_set_vpreg(u32 msr,u64 value)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 
hv_get_vpreg_128(u32 msr,struct hv_get_vp_registers_output * result)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 
hv_get_vpreg(u32 msr)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  */
hyperv_report_panic(struct pt_regs * regs,long err,bool in_die)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_OSID);
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_CRASH_P0, err);
171 	hv_set_vpreg(HV_REGISTER_CRASH_P1, guest_id);
172 	hv_set_vpreg(HV_REGISTER_CRASH_P2, regs->pc);
173 	hv_set_vpreg(HV_REGISTER_CRASH_P3, regs->sp);
174 	hv_set_vpreg(HV_REGISTER_CRASH_P4, 0);
175 
176 	/*
177 	 * Let Hyper-V know there is crash data available
178 	 */
179 	hv_set_vpreg(HV_REGISTER_CRASH_CTL, HV_CRASH_CTL_CRASH_NOTIFY);
180 }
181 EXPORT_SYMBOL_GPL(hyperv_report_panic);
182