linux/arch/x86/hyperv/hv_vtl.c
<<
>>
Prefs
   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Copyright (c) 2023, Microsoft Corporation.
   4 *
   5 * Author:
   6 *   Saurabh Sengar <ssengar@microsoft.com>
   7 */
   8
   9#include <asm/apic.h>
  10#include <asm/boot.h>
  11#include <asm/desc.h>
  12#include <asm/i8259.h>
  13#include <asm/mshyperv.h>
  14#include <asm/realmode.h>
  15
  16extern struct boot_params boot_params;
  17static struct real_mode_header hv_vtl_real_mode_header;
  18
  19void __init hv_vtl_init_platform(void)
  20{
  21        pr_info("Linux runs in Hyper-V Virtual Trust Level\n");
  22
  23        x86_platform.realmode_reserve = x86_init_noop;
  24        x86_platform.realmode_init = x86_init_noop;
  25        x86_init.irqs.pre_vector_init = x86_init_noop;
  26        x86_init.timers.timer_init = x86_init_noop;
  27
  28        /* Avoid searching for BIOS MP tables */
  29        x86_init.mpparse.find_smp_config = x86_init_noop;
  30        x86_init.mpparse.get_smp_config = x86_init_uint_noop;
  31
  32        x86_platform.get_wallclock = get_rtc_noop;
  33        x86_platform.set_wallclock = set_rtc_noop;
  34        x86_platform.get_nmi_reason = hv_get_nmi_reason;
  35
  36        x86_platform.legacy.i8042 = X86_LEGACY_I8042_PLATFORM_ABSENT;
  37        x86_platform.legacy.rtc = 0;
  38        x86_platform.legacy.warm_reset = 0;
  39        x86_platform.legacy.reserve_bios_regions = 0;
  40        x86_platform.legacy.devices.pnpbios = 0;
  41}
  42
  43static inline u64 hv_vtl_system_desc_base(struct ldttss_desc *desc)
  44{
  45        return ((u64)desc->base3 << 32) | ((u64)desc->base2 << 24) |
  46                (desc->base1 << 16) | desc->base0;
  47}
  48
  49static inline u32 hv_vtl_system_desc_limit(struct ldttss_desc *desc)
  50{
  51        return ((u32)desc->limit1 << 16) | (u32)desc->limit0;
  52}
  53
  54typedef void (*secondary_startup_64_fn)(void*, void*);
  55static void hv_vtl_ap_entry(void)
  56{
  57        ((secondary_startup_64_fn)secondary_startup_64)(&boot_params, &boot_params);
  58}
  59
  60static int hv_vtl_bringup_vcpu(u32 target_vp_index, u64 eip_ignored)
  61{
  62        u64 status;
  63        int ret = 0;
  64        struct hv_enable_vp_vtl *input;
  65        unsigned long irq_flags;
  66
  67        struct desc_ptr gdt_ptr;
  68        struct desc_ptr idt_ptr;
  69
  70        struct ldttss_desc *tss;
  71        struct ldttss_desc *ldt;
  72        struct desc_struct *gdt;
  73
  74        u64 rsp = current->thread.sp;
  75        u64 rip = (u64)&hv_vtl_ap_entry;
  76
  77        native_store_gdt(&gdt_ptr);
  78        store_idt(&idt_ptr);
  79
  80        gdt = (struct desc_struct *)((void *)(gdt_ptr.address));
  81        tss = (struct ldttss_desc *)(gdt + GDT_ENTRY_TSS);
  82        ldt = (struct ldttss_desc *)(gdt + GDT_ENTRY_LDT);
  83
  84        local_irq_save(irq_flags);
  85
  86        input = *this_cpu_ptr(hyperv_pcpu_input_arg);
  87        memset(input, 0, sizeof(*input));
  88
  89        input->partition_id = HV_PARTITION_ID_SELF;
  90        input->vp_index = target_vp_index;
  91        input->target_vtl.target_vtl = HV_VTL_MGMT;
  92
  93        /*
  94         * The x86_64 Linux kernel follows the 16-bit -> 32-bit -> 64-bit
  95         * mode transition sequence after waking up an AP with SIPI whose
  96         * vector points to the 16-bit AP startup trampoline code. Here in
  97         * VTL2, we can't perform that sequence as the AP has to start in
  98         * the 64-bit mode.
  99         *
 100         * To make this happen, we tell the hypervisor to load a valid 64-bit
 101         * context (most of which is just magic numbers from the CPU manual)
 102         * so that AP jumps right to the 64-bit entry of the kernel, and the
 103         * control registers are loaded with values that let the AP fetch the
 104         * code and data and carry on with work it gets assigned.
 105         */
 106
 107        input->vp_context.rip = rip;
 108        input->vp_context.rsp = rsp;
 109        input->vp_context.rflags = 0x0000000000000002;
 110        input->vp_context.efer = __rdmsr(MSR_EFER);
 111        input->vp_context.cr0 = native_read_cr0();
 112        input->vp_context.cr3 = __native_read_cr3();
 113        input->vp_context.cr4 = native_read_cr4();
 114        input->vp_context.msr_cr_pat = __rdmsr(MSR_IA32_CR_PAT);
 115        input->vp_context.idtr.limit = idt_ptr.size;
 116        input->vp_context.idtr.base = idt_ptr.address;
 117        input->vp_context.gdtr.limit = gdt_ptr.size;
 118        input->vp_context.gdtr.base = gdt_ptr.address;
 119
 120        /* Non-system desc (64bit), long, code, present */
 121        input->vp_context.cs.selector = __KERNEL_CS;
 122        input->vp_context.cs.base = 0;
 123        input->vp_context.cs.limit = 0xffffffff;
 124        input->vp_context.cs.attributes = 0xa09b;
 125        /* Non-system desc (64bit), data, present, granularity, default */
 126        input->vp_context.ss.selector = __KERNEL_DS;
 127        input->vp_context.ss.base = 0;
 128        input->vp_context.ss.limit = 0xffffffff;
 129        input->vp_context.ss.attributes = 0xc093;
 130
 131        /* System desc (128bit), present, LDT */
 132        input->vp_context.ldtr.selector = GDT_ENTRY_LDT * 8;
 133        input->vp_context.ldtr.base = hv_vtl_system_desc_base(ldt);
 134        input->vp_context.ldtr.limit = hv_vtl_system_desc_limit(ldt);
 135        input->vp_context.ldtr.attributes = 0x82;
 136
 137        /* System desc (128bit), present, TSS, 0x8b - busy, 0x89 -- default */
 138        input->vp_context.tr.selector = GDT_ENTRY_TSS * 8;
 139        input->vp_context.tr.base = hv_vtl_system_desc_base(tss);
 140        input->vp_context.tr.limit = hv_vtl_system_desc_limit(tss);
 141        input->vp_context.tr.attributes = 0x8b;
 142
 143        status = hv_do_hypercall(HVCALL_ENABLE_VP_VTL, input, NULL);
 144
 145        if (!hv_result_success(status) &&
 146            hv_result(status) != HV_STATUS_VTL_ALREADY_ENABLED) {
 147                pr_err("HVCALL_ENABLE_VP_VTL failed for VP : %d ! [Err: %#llx\n]",
 148                       target_vp_index, status);
 149                ret = -EINVAL;
 150                goto free_lock;
 151        }
 152
 153        status = hv_do_hypercall(HVCALL_START_VP, input, NULL);
 154
 155        if (!hv_result_success(status)) {
 156                pr_err("HVCALL_START_VP failed for VP : %d ! [Err: %#llx]\n",
 157                       target_vp_index, status);
 158                ret = -EINVAL;
 159        }
 160
 161free_lock:
 162        local_irq_restore(irq_flags);
 163
 164        return ret;
 165}
 166
 167static int hv_vtl_apicid_to_vp_id(u32 apic_id)
 168{
 169        u64 control;
 170        u64 status;
 171        unsigned long irq_flags;
 172        struct hv_get_vp_from_apic_id_in *input;
 173        u32 *output, ret;
 174
 175        local_irq_save(irq_flags);
 176
 177        input = *this_cpu_ptr(hyperv_pcpu_input_arg);
 178        memset(input, 0, sizeof(*input));
 179        input->partition_id = HV_PARTITION_ID_SELF;
 180        input->apic_ids[0] = apic_id;
 181
 182        output = (u32 *)input;
 183
 184        control = HV_HYPERCALL_REP_COMP_1 | HVCALL_GET_VP_ID_FROM_APIC_ID;
 185        status = hv_do_hypercall(control, input, output);
 186        ret = output[0];
 187
 188        local_irq_restore(irq_flags);
 189
 190        if (!hv_result_success(status)) {
 191                pr_err("failed to get vp id from apic id %d, status %#llx\n",
 192                       apic_id, status);
 193                return -EINVAL;
 194        }
 195
 196        return ret;
 197}
 198
 199static int hv_vtl_wakeup_secondary_cpu(u32 apicid, unsigned long start_eip)
 200{
 201        int vp_id;
 202
 203        pr_debug("Bringing up CPU with APIC ID %d in VTL2...\n", apicid);
 204        vp_id = hv_vtl_apicid_to_vp_id(apicid);
 205
 206        if (vp_id < 0) {
 207                pr_err("Couldn't find CPU with APIC ID %d\n", apicid);
 208                return -EINVAL;
 209        }
 210        if (vp_id > ms_hyperv.max_vp_index) {
 211                pr_err("Invalid CPU id %d for APIC ID %d\n", vp_id, apicid);
 212                return -EINVAL;
 213        }
 214
 215        return hv_vtl_bringup_vcpu(vp_id, start_eip);
 216}
 217
 218int __init hv_vtl_early_init(void)
 219{
 220        /*
 221         * `boot_cpu_has` returns the runtime feature support,
 222         * and here is the earliest it can be used.
 223         */
 224        if (cpu_feature_enabled(X86_FEATURE_XSAVE))
 225                panic("XSAVE has to be disabled as it is not supported by this module.\n"
 226                          "Please add 'noxsave' to the kernel command line.\n");
 227
 228        real_mode_header = &hv_vtl_real_mode_header;
 229        apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu);
 230
 231        return 0;
 232}
 233