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Piccoli" Subject: [PATCH v13 09/11] x86/smpboot: Support parallel startup of secondary CPUs Date: Thu, 2 Mar 2023 11:12:25 +0000 Message-Id: <20230302111227.2102545-10-usama.arif@bytedance.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230302111227.2102545-1-usama.arif@bytedance.com> References: <20230302111227.2102545-1-usama.arif@bytedance.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: David Woodhouse Rework the real-mode startup code to allow for APs to be brought up in parallel. This is in two parts: 1. Introduce a bit-spinlock to prevent them from all using the real mode stack at the same time. 2. Avoid needing to use the global smpboot_control variable to pass each AP its CPU#. To achieve the latter, export the cpuid_to_apicid[] array so that each AP can find its own CPU# by searching therein based on its APIC ID. Introduce flags in the top bits of smpboot_control which indicate methods by which an AP should find its CPU#. For a serialized bringup, the CPU# is explicitly passed in the low bits of smpboot_control as before. For parallel mode there are flags directing the AP to find its APIC ID in CPUID leaf 0x0b (for X2APIC mode) or CPUID leaf 0x01 where 8 bits are sufficient, then perform the cpuid_to_apicid[] lookup with that. Parallel startup may be disabled by a command line option, and also if: • AMD SEV-ES is in use, since the AP may not use CPUID that early. • X2APIC is enabled, but CPUID leaf 0xb is not present and correct. • X2APIC is not enabled but not even CPUID leaf 0x01 exists. Aside from the fact that APs will now look up their CPU# via the newly-exported cpuid_to_apicid[] table, there is no behavioural change intended yet, since new parallel CPUHP states have not — yet — been added. [ tglx: Initial proof of concept patch with bitlock and APIC ID lookup ] [ dwmw2: Rework and testing, commit message, CPUID 0x1 and CPU0 support ] [ seanc: Fix stray override of initial_gs in common_cpu_up() ] [ Oleksandr Natalenko: reported suspend/resume issue fixed in x86_acpi_suspend_lowlevel ] Co-developed-by: Thomas Gleixner Co-developed-by: Brian Gerst Signed-off-by: Thomas Gleixner Signed-off-by: Brian Gerst Signed-off-by: David Woodhouse Signed-off-by: Usama Arif Tested-by: Paul E. McKenney Tested-by: Kim Phillips Tested-by: Oleksandr Natalenko Tested-by: Guilherme G. Piccoli --- .../admin-guide/kernel-parameters.txt | 3 + arch/x86/include/asm/realmode.h | 3 + arch/x86/include/asm/smp.h | 6 ++ arch/x86/kernel/acpi/sleep.c | 9 ++- arch/x86/kernel/apic/apic.c | 2 +- arch/x86/kernel/head_64.S | 64 +++++++++++++++++++ arch/x86/kernel/smpboot.c | 53 ++++++++++++++- arch/x86/realmode/init.c | 3 + arch/x86/realmode/rm/trampoline_64.S | 27 ++++++-- 9 files changed, 162 insertions(+), 8 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 6cfa6e3996cf..7bb7020f97e2 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3819,6 +3819,9 @@ nomodule Disable module load + no_parallel_bringup + [X86,SMP] Disable parallel bring-up of secondary cores. + nopat [X86] Disable PAT (page attribute table extension of pagetables) support. diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h index f6a1737c77be..87e5482acd0d 100644 --- a/arch/x86/include/asm/realmode.h +++ b/arch/x86/include/asm/realmode.h @@ -52,6 +52,7 @@ struct trampoline_header { u64 efer; u32 cr4; u32 flags; + u32 lock; #endif }; @@ -64,6 +65,8 @@ extern unsigned long initial_stack; extern unsigned long initial_vc_handler; #endif +extern u32 *trampoline_lock; + extern unsigned char real_mode_blob[]; extern unsigned char real_mode_relocs[]; diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h index bf2c51df9e0b..1cf4f1e57570 100644 --- a/arch/x86/include/asm/smp.h +++ b/arch/x86/include/asm/smp.h @@ -203,4 +203,10 @@ extern unsigned int smpboot_control; #endif /* !__ASSEMBLY__ */ +/* Control bits for startup_64 */ +#define STARTUP_APICID_CPUID_0B 0x80000000 +#define STARTUP_APICID_CPUID_01 0x40000000 + +#define STARTUP_PARALLEL_MASK (STARTUP_APICID_CPUID_01 | STARTUP_APICID_CPUID_0B) + #endif /* _ASM_X86_SMP_H */ diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c index 1328c221af30..6dfecb27b846 100644 --- a/arch/x86/kernel/acpi/sleep.c +++ b/arch/x86/kernel/acpi/sleep.c @@ -16,6 +16,7 @@ #include #include #include +#include #include #include "../../realmode/rm/wakeup.h" @@ -127,7 +128,13 @@ int x86_acpi_suspend_lowlevel(void) * value is in the actual %rsp register. */ current->thread.sp = (unsigned long)temp_stack + sizeof(temp_stack); - smpboot_control = smp_processor_id(); + /* + * Ensure the CPU knows which one it is when it comes back, if + * it isn't in parallel mode and expected to work that out for + * itself. + */ + if (!(smpboot_control & STARTUP_PARALLEL_MASK)) + smpboot_control = smp_processor_id(); #endif initial_code = (unsigned long)wakeup_long64; saved_magic = 0x123456789abcdef0L; diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index 20d9a604da7c..ac1d7e5da1f2 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -2377,7 +2377,7 @@ static int nr_logical_cpuids = 1; /* * Used to store mapping between logical CPU IDs and APIC IDs. */ -static int cpuid_to_apicid[] = { +int cpuid_to_apicid[] = { [0 ... NR_CPUS - 1] = -1, }; diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 6a8238702eab..c35f7c173832 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -25,6 +25,7 @@ #include #include #include +#include /* * We are not able to switch in one step to the final KERNEL ADDRESS SPACE @@ -234,8 +235,61 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) ANNOTATE_NOENDBR // above #ifdef CONFIG_SMP + /* + * For parallel boot, the APIC ID is retrieved from CPUID, and then + * used to look up the CPU number. For booting a single CPU, the + * CPU number is encoded in smpboot_control. + * + * Bit 31 STARTUP_APICID_CPUID_0B flag (use CPUID 0x0b) + * Bit 30 STARTUP_APICID_CPUID_01 flag (use CPUID 0x01) + * Bit 0-24 CPU# if STARTUP_APICID_CPUID_xx flags are not set + */ movl smpboot_control(%rip), %ecx + testl $STARTUP_APICID_CPUID_0B, %ecx + jnz .Luse_cpuid_0b + testl $STARTUP_APICID_CPUID_01, %ecx + jnz .Luse_cpuid_01 + andl $0x0FFFFFFF, %ecx + jmp .Lsetup_cpu + +.Luse_cpuid_01: + mov $0x01, %eax + cpuid + mov %ebx, %edx + shr $24, %edx + jmp .Lsetup_AP +.Luse_cpuid_0b: + mov $0x0B, %eax + xorl %ecx, %ecx + cpuid + +.Lsetup_AP: + /* EDX contains the APIC ID of the current CPU */ + xorq %rcx, %rcx + leaq cpuid_to_apicid(%rip), %rbx + +.Lfind_cpunr: + cmpl (%rbx,%rcx,4), %edx + jz .Lsetup_cpu + inc %ecx +#ifdef CONFIG_FORCE_NR_CPUS + cmpl $NR_CPUS, %ecx +#else + cmpl nr_cpu_ids(%rip), %ecx +#endif + jb .Lfind_cpunr + + /* APIC ID not found in the table. Drop the trampoline lock and bail. */ + movq trampoline_lock(%rip), %rax + lock + btrl $0, (%rax) + +1: cli + hlt + jmp 1b + +.Lsetup_cpu: /* Get the per cpu offset for the given CPU# which is in ECX */ movq __per_cpu_offset(,%rcx,8), %rdx #else @@ -293,6 +347,14 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) shrq $32, %rdx wrmsr + /* Drop the realmode protection. For the boot CPU the pointer is NULL! */ + movq trampoline_lock(%rip), %rax + testq %rax, %rax + jz .Lsetup_idt + lock + btrl $0, (%rax) + +.Lsetup_idt: /* Setup and Load IDT */ pushq %rsi call early_setup_idt @@ -435,6 +497,8 @@ SYM_DATA(initial_code, .quad x86_64_start_kernel) #ifdef CONFIG_AMD_MEM_ENCRYPT SYM_DATA(initial_vc_handler, .quad handle_vc_boot_ghcb) #endif + +SYM_DATA(trampoline_lock, .quad 0); __FINITDATA __INIT diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index b04520085582..19b9b89b7458 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -797,6 +797,16 @@ static int __init cpu_init_udelay(char *str) } early_param("cpu_init_udelay", cpu_init_udelay); +static bool do_parallel_bringup __ro_after_init = true; + +static int __init no_parallel_bringup(char *str) +{ + do_parallel_bringup = false; + + return 0; +} +early_param("no_parallel_bringup", no_parallel_bringup); + static void __init smp_quirk_init_udelay(void) { /* if cmdline changed it from default, leave it alone */ @@ -1113,7 +1123,7 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle, if (IS_ENABLED(CONFIG_X86_32)) { early_gdt_descr.address = (unsigned long)get_cpu_gdt_rw(cpu); initial_stack = idle->thread.sp; - } else { + } else if (!do_parallel_bringup) { smpboot_control = cpu; } @@ -1515,6 +1525,47 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus) speculative_store_bypass_ht_init(); + /* + * We can do 64-bit AP bringup in parallel if the CPU reports + * its APIC ID in CPUID (either leaf 0x0B if we need the full + * APIC ID in X2APIC mode, or leaf 0x01 if 8 bits are + * sufficient). Otherwise it's too hard. And not for SEV-ES + * guests because they can't use CPUID that early. + */ + if (IS_ENABLED(CONFIG_X86_32) || boot_cpu_data.cpuid_level < 1 || + (x2apic_mode && boot_cpu_data.cpuid_level < 0xb) || + cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) + do_parallel_bringup = false; + + if (do_parallel_bringup && x2apic_mode) { + unsigned int eax, ebx, ecx, edx; + + /* + * To support parallel bringup in x2apic mode, the AP will need + * to obtain its APIC ID from CPUID 0x0B, since CPUID 0x01 has + * only 8 bits. Check that it is present and seems correct. + */ + cpuid_count(0xb, 0, &eax, &ebx, &ecx, &edx); + + /* + * AMD says that if executed with an umimplemented level in + * ECX, then it will return all zeroes in EAX. Intel says it + * will return zeroes in both EAX and EBX. Checking only EAX + * should be sufficient. + */ + if (eax) { + pr_debug("Using CPUID 0xb for parallel CPU startup\n"); + smpboot_control = STARTUP_APICID_CPUID_0B; + } else { + pr_info("Disabling parallel bringup because CPUID 0xb looks untrustworthy\n"); + do_parallel_bringup = false; + } + } else if (do_parallel_bringup) { + /* Without X2APIC, what's in CPUID 0x01 should suffice. */ + pr_debug("Using CPUID 0x1 for parallel CPU startup\n"); + smpboot_control = STARTUP_APICID_CPUID_01; + } + snp_set_wakeup_secondary_cpu(); } diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c index af565816d2ba..788e5559549f 100644 --- a/arch/x86/realmode/init.c +++ b/arch/x86/realmode/init.c @@ -154,6 +154,9 @@ static void __init setup_real_mode(void) trampoline_header->flags = 0; + trampoline_lock = &trampoline_header->lock; + *trampoline_lock = 0; + trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd); /* Map the real mode stub as virtual == physical */ diff --git a/arch/x86/realmode/rm/trampoline_64.S b/arch/x86/realmode/rm/trampoline_64.S index e38d61d6562e..2dfb1c400167 100644 --- a/arch/x86/realmode/rm/trampoline_64.S +++ b/arch/x86/realmode/rm/trampoline_64.S @@ -37,6 +37,24 @@ .text .code16 +.macro LOAD_REALMODE_ESP + /* + * Make sure only one CPU fiddles with the realmode stack + */ +.Llock_rm\@: + btl $0, tr_lock + jnc 2f + pause + jmp .Llock_rm\@ +2: + lock + btsl $0, tr_lock + jc .Llock_rm\@ + + # Setup stack + movl $rm_stack_end, %esp +.endm + .balign PAGE_SIZE SYM_CODE_START(trampoline_start) cli # We should be safe anyway @@ -49,8 +67,7 @@ SYM_CODE_START(trampoline_start) mov %ax, %es mov %ax, %ss - # Setup stack - movl $rm_stack_end, %esp + LOAD_REALMODE_ESP call verify_cpu # Verify the cpu supports long mode testl %eax, %eax # Check for return code @@ -93,8 +110,7 @@ SYM_CODE_START(sev_es_trampoline_start) mov %ax, %es mov %ax, %ss - # Setup stack - movl $rm_stack_end, %esp + LOAD_REALMODE_ESP jmp .Lswitch_to_protected SYM_CODE_END(sev_es_trampoline_start) @@ -177,7 +193,7 @@ SYM_CODE_START(pa_trampoline_compat) * In compatibility mode. Prep ESP and DX for startup_32, then disable * paging and complete the switch to legacy 32-bit mode. */ - movl $rm_stack_end, %esp + LOAD_REALMODE_ESP movw $__KERNEL_DS, %dx movl $(CR0_STATE & ~X86_CR0_PG), %eax @@ -241,6 +257,7 @@ SYM_DATA_START(trampoline_header) SYM_DATA(tr_efer, .space 8) SYM_DATA(tr_cr4, .space 4) SYM_DATA(tr_flags, .space 4) + SYM_DATA(tr_lock, .space 4) SYM_DATA_END(trampoline_header) #include "trampoline_common.S"