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 */
24u64 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}
37EXPORT_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
45u64 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}
55EXPORT_SYMBOL_GPL(hv_do_fast_hypercall8);
56
57/*
58 * Set a single VP register to a 64-bit value.
59 */
60void 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}
82EXPORT_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
91void 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}
119EXPORT_SYMBOL_GPL(hv_get_vpreg_128);
120
121u64 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}
129EXPORT_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 */
142void 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}
181EXPORT_SYMBOL_GPL(hyperv_report_panic);
182