diff options
Diffstat (limited to 'arch/x86/hyperv/hv_vtl.c')
| -rw-r--r-- | arch/x86/hyperv/hv_vtl.c | 281 |
1 files changed, 281 insertions, 0 deletions
diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c new file mode 100644 index 000000000000..c0edaed0efb3 --- /dev/null +++ b/arch/x86/hyperv/hv_vtl.c @@ -0,0 +1,281 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (c) 2023, Microsoft Corporation. + * + * Author: + * Saurabh Sengar <ssengar@microsoft.com> + */ + +#include <asm/apic.h> +#include <asm/boot.h> +#include <asm/desc.h> +#include <asm/fpu/api.h> +#include <asm/fpu/types.h> +#include <asm/i8259.h> +#include <asm/mshyperv.h> +#include <asm/msr.h> +#include <asm/realmode.h> +#include <asm/reboot.h> +#include <asm/smap.h> +#include <linux/export.h> +#include <../kernel/smpboot.h> +#include "../../kernel/fpu/legacy.h" + +extern struct boot_params boot_params; +static struct real_mode_header hv_vtl_real_mode_header; + +static bool __init hv_vtl_msi_ext_dest_id(void) +{ + return true; +} + +/* + * The `native_machine_emergency_restart` function from `reboot.c` writes + * to the physical address 0x472 to indicate the type of reboot for the + * firmware. We cannot have that in VSM as the memory composition might + * be more generic, and such write effectively corrupts the memory thus + * making diagnostics harder at the very least. + */ +static void __noreturn hv_vtl_emergency_restart(void) +{ + /* + * Cause a triple fault and the immediate reset. Here the code does not run + * on the top of any firmware, whereby cannot reach out to its services. + * The inifinite loop is for the improbable case that the triple fault does + * not work and have to preserve the state intact for debugging. + */ + for (;;) { + idt_invalidate(); + __asm__ __volatile__("int3"); + } +} + +/* + * The only way to restart in the VTL mode is to triple fault as the kernel runs + * as firmware. + */ +static void __noreturn hv_vtl_restart(char __maybe_unused *cmd) +{ + hv_vtl_emergency_restart(); +} + +void __init hv_vtl_init_platform(void) +{ + /* + * This function is a no-op if the VTL mode is not enabled. + * If it is, this function runs if and only the kernel boots in + * VTL2 which the x86 hv initialization path makes sure of. + */ + pr_info("Linux runs in Hyper-V Virtual Trust Level %d\n", ms_hyperv.vtl); + + x86_platform.realmode_reserve = x86_init_noop; + x86_platform.realmode_init = x86_init_noop; + x86_init.irqs.pre_vector_init = x86_init_noop; + x86_init.timers.timer_init = x86_init_noop; + x86_init.resources.probe_roms = x86_init_noop; + + /* Avoid searching for BIOS MP tables */ + x86_init.mpparse.find_mptable = x86_init_noop; + x86_init.mpparse.early_parse_smp_cfg = x86_init_noop; + + x86_platform.get_wallclock = get_rtc_noop; + x86_platform.set_wallclock = set_rtc_noop; + x86_platform.get_nmi_reason = hv_get_nmi_reason; + + x86_platform.legacy.i8042 = X86_LEGACY_I8042_PLATFORM_ABSENT; + x86_platform.legacy.rtc = 0; + x86_platform.legacy.warm_reset = 0; + x86_platform.legacy.reserve_bios_regions = 0; + x86_platform.legacy.devices.pnpbios = 0; + + x86_init.hyper.msi_ext_dest_id = hv_vtl_msi_ext_dest_id; +} + +static inline u64 hv_vtl_system_desc_base(struct ldttss_desc *desc) +{ + return ((u64)desc->base3 << 32) | ((u64)desc->base2 << 24) | + (desc->base1 << 16) | desc->base0; +} + +static inline u32 hv_vtl_system_desc_limit(struct ldttss_desc *desc) +{ + return ((u32)desc->limit1 << 16) | (u32)desc->limit0; +} + +typedef void (*secondary_startup_64_fn)(void*, void*); +static void hv_vtl_ap_entry(void) +{ + ((secondary_startup_64_fn)secondary_startup_64)(&boot_params, &boot_params); +} + +static int hv_vtl_bringup_vcpu(u32 target_vp_index, int cpu, u64 eip_ignored) +{ + u64 status; + int ret = 0; + struct hv_enable_vp_vtl *input; + unsigned long irq_flags; + + struct desc_ptr gdt_ptr; + struct desc_ptr idt_ptr; + + struct ldttss_desc *tss; + struct ldttss_desc *ldt; + struct desc_struct *gdt; + + struct task_struct *idle = idle_thread_get(cpu); + u64 rsp = (unsigned long)idle->thread.sp; + + u64 rip = (u64)&hv_vtl_ap_entry; + + native_store_gdt(&gdt_ptr); + store_idt(&idt_ptr); + + gdt = (struct desc_struct *)((void *)(gdt_ptr.address)); + tss = (struct ldttss_desc *)(gdt + GDT_ENTRY_TSS); + ldt = (struct ldttss_desc *)(gdt + GDT_ENTRY_LDT); + + local_irq_save(irq_flags); + + input = *this_cpu_ptr(hyperv_pcpu_input_arg); + memset(input, 0, sizeof(*input)); + + input->partition_id = HV_PARTITION_ID_SELF; + input->vp_index = target_vp_index; + input->target_vtl.target_vtl = HV_VTL_MGMT; + + /* + * The x86_64 Linux kernel follows the 16-bit -> 32-bit -> 64-bit + * mode transition sequence after waking up an AP with SIPI whose + * vector points to the 16-bit AP startup trampoline code. Here in + * VTL2, we can't perform that sequence as the AP has to start in + * the 64-bit mode. + * + * To make this happen, we tell the hypervisor to load a valid 64-bit + * context (most of which is just magic numbers from the CPU manual) + * so that AP jumps right to the 64-bit entry of the kernel, and the + * control registers are loaded with values that let the AP fetch the + * code and data and carry on with work it gets assigned. + */ + + input->vp_context.rip = rip; + input->vp_context.rsp = rsp; + input->vp_context.rflags = 0x0000000000000002; + input->vp_context.efer = native_rdmsrq(MSR_EFER); + input->vp_context.cr0 = native_read_cr0(); + input->vp_context.cr3 = __native_read_cr3(); + input->vp_context.cr4 = native_read_cr4(); + input->vp_context.msr_cr_pat = native_rdmsrq(MSR_IA32_CR_PAT); + input->vp_context.idtr.limit = idt_ptr.size; + input->vp_context.idtr.base = idt_ptr.address; + input->vp_context.gdtr.limit = gdt_ptr.size; + input->vp_context.gdtr.base = gdt_ptr.address; + + /* Non-system desc (64bit), long, code, present */ + input->vp_context.cs.selector = __KERNEL_CS; + input->vp_context.cs.base = 0; + input->vp_context.cs.limit = 0xffffffff; + input->vp_context.cs.attributes = 0xa09b; + /* Non-system desc (64bit), data, present, granularity, default */ + input->vp_context.ss.selector = __KERNEL_DS; + input->vp_context.ss.base = 0; + input->vp_context.ss.limit = 0xffffffff; + input->vp_context.ss.attributes = 0xc093; + + /* System desc (128bit), present, LDT */ + input->vp_context.ldtr.selector = GDT_ENTRY_LDT * 8; + input->vp_context.ldtr.base = hv_vtl_system_desc_base(ldt); + input->vp_context.ldtr.limit = hv_vtl_system_desc_limit(ldt); + input->vp_context.ldtr.attributes = 0x82; + + /* System desc (128bit), present, TSS, 0x8b - busy, 0x89 -- default */ + input->vp_context.tr.selector = GDT_ENTRY_TSS * 8; + input->vp_context.tr.base = hv_vtl_system_desc_base(tss); + input->vp_context.tr.limit = hv_vtl_system_desc_limit(tss); + input->vp_context.tr.attributes = 0x8b; + + status = hv_do_hypercall(HVCALL_ENABLE_VP_VTL, input, NULL); + + if (!hv_result_success(status) && + hv_result(status) != HV_STATUS_VTL_ALREADY_ENABLED) { + pr_err("HVCALL_ENABLE_VP_VTL failed for VP : %d ! [Err: %#llx\n]", + target_vp_index, status); + ret = -EINVAL; + goto free_lock; + } + + status = hv_do_hypercall(HVCALL_START_VP, input, NULL); + + if (!hv_result_success(status)) { + pr_err("HVCALL_START_VP failed for VP : %d ! [Err: %#llx]\n", + target_vp_index, status); + ret = -EINVAL; + } + +free_lock: + local_irq_restore(irq_flags); + + return ret; +} + +static int hv_vtl_wakeup_secondary_cpu(u32 apicid, unsigned long start_eip, unsigned int cpu) +{ + int vp_index; + + pr_debug("Bringing up CPU with APIC ID %d in VTL2...\n", apicid); + vp_index = hv_apicid_to_vp_index(apicid); + + if (vp_index < 0) { + pr_err("Couldn't find CPU with APIC ID %d\n", apicid); + return -EINVAL; + } + if (vp_index > ms_hyperv.max_vp_index) { + pr_err("Invalid CPU id %d for APIC ID %d\n", vp_index, apicid); + return -EINVAL; + } + + return hv_vtl_bringup_vcpu(vp_index, cpu, start_eip); +} + +int __init hv_vtl_early_init(void) +{ + machine_ops.emergency_restart = hv_vtl_emergency_restart; + machine_ops.restart = hv_vtl_restart; + + /* + * `boot_cpu_has` returns the runtime feature support, + * and here is the earliest it can be used. + */ + if (cpu_feature_enabled(X86_FEATURE_XSAVE)) + panic("XSAVE has to be disabled as it is not supported by this module.\n" + "Please add 'noxsave' to the kernel command line.\n"); + + real_mode_header = &hv_vtl_real_mode_header; + apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu); + + return 0; +} + +DEFINE_STATIC_CALL_NULL(__mshv_vtl_return_hypercall, void (*)(void)); + +void mshv_vtl_return_call_init(u64 vtl_return_offset) +{ + static_call_update(__mshv_vtl_return_hypercall, + (void *)((u8 *)hv_hypercall_pg + vtl_return_offset)); +} +EXPORT_SYMBOL(mshv_vtl_return_call_init); + +void mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0) +{ + struct hv_vp_assist_page *hvp; + + hvp = hv_vp_assist_page[smp_processor_id()]; + hvp->vtl_ret_x64rax = vtl0->rax; + hvp->vtl_ret_x64rcx = vtl0->rcx; + + kernel_fpu_begin_mask(0); + fxrstor(&vtl0->fx_state); + __mshv_vtl_return_call(vtl0); + fxsave(&vtl0->fx_state); + kernel_fpu_end(); +} +EXPORT_SYMBOL(mshv_vtl_return_call); |