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[kernel] Pre-allocate cpu_data and pass to APs

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In order to avoid cyclic dependencies in the case of page faults while
bringing up an AP, pre-allocate the cpu_data structure and related CPU
control structures, and pass them to the AP startup code.

This also changes the following:
- cpu_early_init() was split out of cpu_early_init() to allow early
  usage of current_cpu() on the BSP before we're ready for the rest of
  cpu_init(). (These functions were also renamed to follow the preferred
  area_action naming style.)
- isr_handler now zeroes out the IST entry for its vector instead of
  trying to increment the IST stack pointer
- the IST stacks are allocated outside of cpu_init, to also help reduce
  stack pressue and chance of page faults before APs are ready
- share stack areas between AP idle threads so we only waste 1K per
  additional AP for the unused idle stack
This commit is contained in:
Justin C. Miller
2021-02-10 01:19:41 -08:00
parent 872f178d94
commit 2d4a65c654
9 changed files with 159 additions and 104 deletions
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83
src/kernel/main.cpp
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@@ -37,9 +37,9 @@ extern "C" {
void kernel_main(kernel::args::header *header);
void (*__ctors)(void);
void (*__ctors_end)(void);
void long_ap_startup();
void long_ap_startup(cpu_data *cpu);
void ap_startup();
void init_ap_trampoline(void*, uintptr_t, void (*)());
void init_ap_trampoline(void*, cpu_data *, void (*)(cpu_data *));
}
extern void __kernel_assert(const char *, unsigned, const char *);
@@ -118,23 +118,29 @@ kernel_main(args::header *header)
logger_clear_immediate();
}
extern IDT &g_idt;
extern TSS &g_bsp_tss;
extern GDT &g_bsp_gdt;
TSS *tss = new (&g_bsp_tss) TSS;
GDT *gdt = new (&g_bsp_gdt) GDT {tss};
gdt->install();
extern cpu_data g_bsp_cpu_data;
IDT *idt = new (&g_idt) IDT;
idt->install();
cpu_data *cpu = &g_bsp_cpu_data;
kutil::memset(cpu, 0, sizeof(cpu_data));
cpu->self = cpu;
cpu->tss = new (&g_bsp_tss) TSS;
cpu->gdt = new (&g_bsp_gdt) GDT {cpu->tss};
cpu_early_init(cpu);
disable_legacy_pic();
memory_initialize_pre_ctors(*header);
init_cpu(true);
run_constructors();
memory_initialize_post_ctors(*header);
cpu->tss->create_ist_stacks(idt->used_ist_entries());
for (size_t i = 0; i < header->num_modules; ++i) {
args::module &mod = header->modules[i];
void *virt = memory::to_virtual<void>(mod.location);
@@ -154,11 +160,15 @@ kernel_main(args::header *header)
device_manager &devices = device_manager::get();
devices.parse_acpi(header->acpi_table);
// cpu_init relies on the APIC being set up
cpu_init(cpu, true);
devices.init_drivers();
devices.get_lapic().calibrate_timer();
start_aps(header->pml4);
idt->add_ist_entries();
interrupts_enable();
/*
@@ -216,8 +226,8 @@ start_aps(void *kpml4)
// Since we're using address space outside kernel space, make sure
// the kernel's vm_space is used
cpu_data &cpu = current_cpu();
cpu.process = &g_kernel_process;
cpu_data &bsp = current_cpu();
bsp.process = &g_kernel_process;
// Copy the startup code somwhere the real mode trampoline can run
uintptr_t addr = 0x8000; // TODO: find a valid address, rewrite addresses
@@ -229,36 +239,69 @@ start_aps(void *kpml4)
reinterpret_cast<void*>(&ap_startup),
ap_startup_code_size);
static constexpr size_t stack_bytes = kernel_stack_pages * frame_size;
// AP idle stacks need less room than normal stacks, so pack multiple
// into a normal stack area
static constexpr size_t idle_stack_bytes = 1024; // 2KiB is generous
static constexpr size_t full_stack_bytes = kernel_stack_pages * frame_size;
static constexpr size_t idle_stacks_per = full_stack_bytes / idle_stack_bytes;
uint8_t ist_entries = IDT::get().used_ist_entries();
size_t free_stack_count = 0;
uintptr_t stack_area_start = 0;
for (uint8_t id : ids) {
if (id == apic.get_id()) continue;
log::info(logs::boot, "Starting AP %d", id);
size_t current_count = ap_startup_count;
uintptr_t stack_start = g_kernel_stacks.get_section();
uintptr_t stack_end = stack_start + stack_bytes - 2 * sizeof(void*);
// Set up the CPU data structures
TSS *tss = new TSS;
GDT *gdt = new GDT {tss};
cpu_data *cpu = new cpu_data;
kutil::memset(cpu, 0, sizeof(cpu_data));
cpu->self = cpu;
cpu->gdt = gdt;
cpu->tss = tss;
tss->create_ist_stacks(ist_entries);
// Set up the CPU's idle task stack
if (free_stack_count == 0) {
stack_area_start = g_kernel_stacks.get_section();
free_stack_count = idle_stacks_per;
}
uintptr_t stack_end = stack_area_start + free_stack_count-- * idle_stack_bytes;
stack_end -= 2 * sizeof(void*); // Null frame
*reinterpret_cast<uint64_t*>(stack_end) = 0; // pre-fault the page
cpu->rsp0 = stack_end;
init_ap_trampoline(kpml4, stack_end, long_ap_startup);
// Set up the trampoline with this CPU's data
init_ap_trampoline(kpml4, cpu, long_ap_startup);
// Kick it off!
size_t current_count = ap_startup_count;
log::debug(logs::boot, "Starting AP %d: stack %llx", id, stack_end);
apic.send_ipi(lapic::ipi_mode::init, 0, id);
clk.spinwait(1000);
apic.send_ipi(lapic::ipi_mode::startup, vector, id);
for (unsigned i = 0; i < 20; ++i) {
if (ap_startup_count > current_count) break;
clk.spinwait(10);
clk.spinwait(20);
}
// If the CPU already incremented ap_startup_count, it's done
if (ap_startup_count > current_count)
continue;
// Send the second SIPI (intel recommends this)
apic.send_ipi(lapic::ipi_mode::startup, vector, id);
for (unsigned i = 0; i < 100; ++i) {
if (ap_startup_count > current_count) break;
clk.spinwait(10);
clk.spinwait(100);
}
log::warn(logs::boot, "No response from AP %d within timeout", id);
}
log::info(logs::boot, "%d CPUs running", ap_startup_count);
@@ -266,9 +309,9 @@ start_aps(void *kpml4)
}
void
long_ap_startup()
long_ap_startup(cpu_data *cpu)
{
init_cpu(false);
cpu_init(cpu, false);
++ap_startup_count;
while(1) asm("hlt");