LXR linux/arch/arm64/hyperv/hv

   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_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}
 181EXPORT_SYMBOL_GPL(hyperv_report_panic);
 182