| Message ID | 20230316222109.1940300-10-usama.arif@bytedance.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Parallel CPU bringup for x86_64 | expand |
On Thu, Mar 16, 2023 at 6:21 PM Usama Arif <usama.arif@bytedance.com> wrote: > > From: David Woodhouse <dwmw@amazon.co.uk> > > 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 <tglx@linutronix.de> > Co-developed-by: Brian Gerst <brgerst@gmail.com> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Signed-off-by: Brian Gerst <brgerst@gmail.com> > Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> > Signed-off-by: Usama Arif <usama.arif@bytedance.com> > Tested-by: Paul E. McKenney <paulmck@kernel.org> > Tested-by: Kim Phillips <kim.phillips@amd.com> > Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name> > Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> > --- > .../admin-guide/kernel-parameters.txt | 3 + > arch/x86/include/asm/cpu.h | 1 + > 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/cpu/topology.c | 3 +- > arch/x86/kernel/head_64.S | 65 +++++++++++++++++++ > arch/x86/kernel/smpboot.c | 50 +++++++++++++- > arch/x86/realmode/init.c | 3 + > arch/x86/realmode/rm/trampoline_64.S | 27 ++++++-- > 11 files changed, 163 insertions(+), 9 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/cpu.h b/arch/x86/include/asm/cpu.h > index 78796b98a544..ef8ba318dca1 100644 > --- a/arch/x86/include/asm/cpu.h > +++ b/arch/x86/include/asm/cpu.h > @@ -97,5 +97,6 @@ static inline bool intel_cpu_signatures_match(unsigned int s1, unsigned int p1, > extern u64 x86_read_arch_cap_msr(void); > int intel_find_matching_signature(void *mc, unsigned int csig, int cpf); > int intel_microcode_sanity_check(void *mc, bool print_err, int hdr_type); > +int check_extended_topology_leaf(int leaf); > > #endif /* _ASM_X86_CPU_H */ > 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 <asm/cacheflush.h> > #include <asm/realmode.h> > #include <asm/hypervisor.h> > +#include <asm/smp.h> > > #include <linux/ftrace.h> > #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/cpu/topology.c b/arch/x86/kernel/cpu/topology.c > index 5e868b62a7c4..4373442e500a 100644 > --- a/arch/x86/kernel/cpu/topology.c > +++ b/arch/x86/kernel/cpu/topology.c > @@ -9,6 +9,7 @@ > #include <asm/apic.h> > #include <asm/memtype.h> > #include <asm/processor.h> > +#include <asm/cpu.h> > > #include "cpu.h" > > @@ -32,7 +33,7 @@ EXPORT_SYMBOL(__max_die_per_package); > /* > * Check if given CPUID extended topology "leaf" is implemented > */ > -static int check_extended_topology_leaf(int leaf) > +int check_extended_topology_leaf(int leaf) > { > unsigned int eax, ebx, ecx, edx; > > diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S > index 6a8238702eab..65bca47d84a1 100644 > --- a/arch/x86/kernel/head_64.S > +++ b/arch/x86/kernel/head_64.S > @@ -25,6 +25,7 @@ > #include <asm/export.h> > #include <asm/nospec-branch.h> > #include <asm/fixmap.h> > +#include <asm/smp.h> > > /* > * 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 > @@ -264,6 +318,14 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) > lgdt (%rsp) > addq $16, %rsp > > + /* Drop the realmode protection. For the boot CPU the pointer is NULL! */ > + movq trampoline_lock(%rip), %rax > + testq %rax, %rax > + jz .Lsetup_data_segments > + lock > + btrl $0, (%rax) > + > +.Lsetup_data_segments: > /* set up data segments */ > xorl %eax,%eax > movl %eax,%ds This can still go earlier, right after "movq TASK_threadsp(%rax), %rsp". The GDT descriptor is placed on the idle thread stack, so it's safe to drop the lock before it. -- Brian Gerst
On Tue, 2023-03-21 at 14:28 -0400, Brian Gerst wrote: > > > @@ -264,6 +318,14 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) > > lgdt (%rsp) > > addq $16, %rsp > > > > + /* Drop the realmode protection. For the boot CPU the pointer is NULL! */ > > + movq trampoline_lock(%rip), %rax > > + testq %rax, %rax > > + jz .Lsetup_data_segments > > + lock > > + btrl $0, (%rax) > > + > > +.Lsetup_data_segments: > > /* set up data segments */ > > xorl %eax,%eax > > movl %eax,%ds > > This can still go earlier, right after "movq TASK_threadsp(%rax), > %rsp". The GDT descriptor is placed on the idle thread stack, so it's > safe to drop the lock before it. --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -335,6 +335,17 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) movq pcpu_hot + X86_current_task(%rdx), %rax movq TASK_threadsp(%rax), %rsp + /* + * Now that this CPU is running on its own stack, drop the realmode + * protection. For the boot CPU the pointer is NULL! + */ + movq trampoline_lock(%rip), %rax + testq %rax, %rax + jz .Lsetup_gdt + lock + btrl $0, (%rax) + +.Lsetup_gdt: /* * We must switch to a new descriptor in kernel space for the GDT * because soon the kernel won't have access anymore to the userspace @@ -377,14 +388,6 @@ 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
On Tue, Mar 21, 2023 at 3:12 PM David Woodhouse <dwmw2@infradead.org> wrote: > > On Tue, 2023-03-21 at 14:28 -0400, Brian Gerst wrote: > > > > > @@ -264,6 +318,14 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) > > > lgdt (%rsp) > > > addq $16, %rsp > > > > > > + /* Drop the realmode protection. For the boot CPU the pointer is NULL! */ > > > + movq trampoline_lock(%rip), %rax > > > + testq %rax, %rax > > > + jz .Lsetup_data_segments > > > + lock > > > + btrl $0, (%rax) > > > + > > > +.Lsetup_data_segments: > > > /* set up data segments */ > > > xorl %eax,%eax > > > movl %eax,%ds > > > > This can still go earlier, right after "movq TASK_threadsp(%rax), > > %rsp". The GDT descriptor is placed on the idle thread stack, so it's > > safe to drop the lock before it. > > > --- a/arch/x86/kernel/head_64.S > +++ b/arch/x86/kernel/head_64.S > @@ -335,6 +335,17 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) > movq pcpu_hot + X86_current_task(%rdx), %rax > movq TASK_threadsp(%rax), %rsp > > + /* > + * Now that this CPU is running on its own stack, drop the realmode > + * protection. For the boot CPU the pointer is NULL! > + */ > + movq trampoline_lock(%rip), %rax > + testq %rax, %rax > + jz .Lsetup_gdt > + lock > + btrl $0, (%rax) > + > +.Lsetup_gdt: > /* > * We must switch to a new descriptor in kernel space for the GDT > * because soon the kernel won't have access anymore to the userspace > @@ -377,14 +388,6 @@ 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 > Looks good, thanks.
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/cpu.h b/arch/x86/include/asm/cpu.h index 78796b98a544..ef8ba318dca1 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -97,5 +97,6 @@ static inline bool intel_cpu_signatures_match(unsigned int s1, unsigned int p1, extern u64 x86_read_arch_cap_msr(void); int intel_find_matching_signature(void *mc, unsigned int csig, int cpf); int intel_microcode_sanity_check(void *mc, bool print_err, int hdr_type); +int check_extended_topology_leaf(int leaf); #endif /* _ASM_X86_CPU_H */ 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 <asm/cacheflush.h> #include <asm/realmode.h> #include <asm/hypervisor.h> +#include <asm/smp.h> #include <linux/ftrace.h> #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/cpu/topology.c b/arch/x86/kernel/cpu/topology.c index 5e868b62a7c4..4373442e500a 100644 --- a/arch/x86/kernel/cpu/topology.c +++ b/arch/x86/kernel/cpu/topology.c @@ -9,6 +9,7 @@ #include <asm/apic.h> #include <asm/memtype.h> #include <asm/processor.h> +#include <asm/cpu.h> #include "cpu.h" @@ -32,7 +33,7 @@ EXPORT_SYMBOL(__max_die_per_package); /* * Check if given CPUID extended topology "leaf" is implemented */ -static int check_extended_topology_leaf(int leaf) +int check_extended_topology_leaf(int leaf) { unsigned int eax, ebx, ecx, edx; diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 6a8238702eab..65bca47d84a1 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -25,6 +25,7 @@ #include <asm/export.h> #include <asm/nospec-branch.h> #include <asm/fixmap.h> +#include <asm/smp.h> /* * 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 @@ -264,6 +318,14 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) lgdt (%rsp) addq $16, %rsp + /* Drop the realmode protection. For the boot CPU the pointer is NULL! */ + movq trampoline_lock(%rip), %rax + testq %rax, %rax + jz .Lsetup_data_segments + lock + btrl $0, (%rax) + +.Lsetup_data_segments: /* set up data segments */ xorl %eax,%eax movl %eax,%ds @@ -293,6 +355,7 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) shrq $32, %rdx wrmsr +.Lsetup_idt: /* Setup and Load IDT */ pushq %rsi call early_setup_idt @@ -435,6 +498,8 @@ 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 28d1643eee99..a9e48946fc89 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; } @@ -1473,6 +1483,41 @@ void __init smp_prepare_cpus_common(void) set_cpu_sibling_map(0); } +/* + * 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. + */ +static bool prepare_parallel_bringup(void) +{ + if (IS_ENABLED(CONFIG_X86_32) || cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) + return false; + + if (x2apic_mode) { + if (boot_cpu_data.cpuid_level < 0x0b) + return false; + + if (check_extended_topology_leaf(0x0b) != 0) { + pr_info("Disabling parallel bringup because CPUID 0xb looks untrustworthy\n"); + return false; + } + + pr_debug("Using CPUID 0xb for parallel CPU startup\n"); + smpboot_control = STARTUP_APICID_CPUID_0B; + } else { + /* Without X2APIC, what's in CPUID 0x01 should suffice. */ + if (boot_cpu_data.cpuid_level < 0x01) + return false; + + pr_debug("Using CPUID 0x1 for parallel CPU startup\n"); + smpboot_control = STARTUP_APICID_CPUID_01; + } + + return true; +} + /* * Prepare for SMP bootup. * @max_cpus: configured maximum number of CPUs, It is a legacy parameter @@ -1513,6 +1558,9 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus) speculative_store_bypass_ht_init(); + if (do_parallel_bringup) + do_parallel_bringup = prepare_parallel_bringup(); + 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"