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Date: Fri, 18 Feb 2011 07:16:53 -0500
From: Brian Gerst <brgerst@...il.com>
To: mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
castet.matthieu@...e.fr, tglx@...utronix.de, sfr@...b.auug.org.au,
hpa@...ux.intel.com, rjw@...k.pl
Subject: Re: [tip:x86/trampoline] x86, trampoline: Common infrastructure for
low memory trampolines
On Fri, Feb 18, 2011 at 12:19 AM, tip-bot for H. Peter Anvin
<hpa@...ux.intel.com> wrote:
> Commit-ID: 4822b7fc6d4870685a9feadfc348d48f5e47460a
> Gitweb: http://git.kernel.org/tip/4822b7fc6d4870685a9feadfc348d48f5e47460a
> Author: H. Peter Anvin <hpa@...ux.intel.com>
> AuthorDate: Mon, 14 Feb 2011 15:34:57 -0800
> Committer: H. Peter Anvin <hpa@...ux.intel.com>
> CommitDate: Thu, 17 Feb 2011 21:02:43 -0800
>
> x86, trampoline: Common infrastructure for low memory trampolines
>
> Common infrastructure for low memory trampolines. This code installs
> the trampolines permanently in low memory very early. It also permits
> multiple pieces of code to be used for this purpose.
>
> This code also introduces a standard infrastructure for computing
> symbol addresses in the trampoline code.
>
> The only change to the actual SMP trampolines themselves is that the
> 64-bit trampoline has been made reusable -- the previous version would
> overwrite the code with a status variable; this moves the status
> variable to a separate location.
>
> Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
> LKML-Reference: <4D5DFBE4.7090104@...el.com>
> Cc: Rafael J. Wysocki <rjw@...k.pl>
> Cc: Matthieu Castet <castet.matthieu@...e.fr>
> Cc: Stephen Rothwell <sfr@...b.auug.org.au>
> ---
> arch/x86/Kconfig | 4 ---
> arch/x86/kernel/Makefile | 3 +-
> arch/x86/kernel/head32.c | 9 --------
> arch/x86/kernel/head_64.S | 3 +-
> arch/x86/kernel/setup.c | 2 +-
> arch/x86/kernel/smpboot.c | 10 +++++---
> arch/x86/kernel/trampoline.c | 42 ++++++++++++++++++++------------------
> arch/x86/kernel/trampoline_32.S | 15 ++++++++++---
> arch/x86/kernel/trampoline_64.S | 30 ++++++++++++++++-----------
> arch/x86/kernel/vmlinux.lds.S | 13 ++++++++++++
> 10 files changed, 73 insertions(+), 58 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index d5ed94d..1359bc9 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -217,10 +217,6 @@ config X86_HT
> def_bool y
> depends on SMP
>
> -config X86_TRAMPOLINE
> - def_bool y
> - depends on SMP || (64BIT && ACPI_SLEEP)
> -
> config X86_32_LAZY_GS
> def_bool y
> depends on X86_32 && !CC_STACKPROTECTOR
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 34244b2..2e8ce0d 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -47,7 +47,7 @@ obj-y += tsc.o io_delay.o rtc.o
> obj-y += pci-iommu_table.o
> obj-y += resource.o
>
> -obj-$(CONFIG_X86_TRAMPOLINE) += trampoline.o
> +obj-y += trampoline.o trampoline_$(BITS).o
> obj-y += process.o
> obj-y += i387.o xsave.o
> obj-y += ptrace.o
> @@ -69,7 +69,6 @@ obj-$(CONFIG_SMP) += smp.o
> obj-$(CONFIG_SMP) += smpboot.o tsc_sync.o
> obj-$(CONFIG_SMP) += setup_percpu.o
> obj-$(CONFIG_X86_64_SMP) += tsc_sync.o
> -obj-$(CONFIG_X86_TRAMPOLINE) += trampoline_$(BITS).o
> obj-$(CONFIG_X86_MPPARSE) += mpparse.o
> obj-y += apic/
> obj-$(CONFIG_X86_REBOOTFIXUPS) += reboot_fixups_32.o
> diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c
> index 7f138b3..d6d6bb3 100644
> --- a/arch/x86/kernel/head32.c
> +++ b/arch/x86/kernel/head32.c
> @@ -34,15 +34,6 @@ void __init i386_start_kernel(void)
> {
> memblock_init();
>
> -#ifdef CONFIG_X86_TRAMPOLINE
> - /*
> - * But first pinch a few for the stack/trampoline stuff
> - * FIXME: Don't need the extra page at 4K, but need to fix
> - * trampoline before removing it. (see the GDT stuff)
> - */
> - memblock_x86_reserve_range(PAGE_SIZE, PAGE_SIZE + PAGE_SIZE, "EX TRAMPOLINE");
> -#endif
> -
> memblock_x86_reserve_range(__pa_symbol(&_text), __pa_symbol(&__bss_stop), "TEXT DATA BSS");
>
> #ifdef CONFIG_BLK_DEV_INITRD
> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
> index 239046b..e11e394 100644
> --- a/arch/x86/kernel/head_64.S
> +++ b/arch/x86/kernel/head_64.S
> @@ -136,10 +136,9 @@ ident_complete:
> /* Fixup phys_base */
> addq %rbp, phys_base(%rip)
>
> -#ifdef CONFIG_X86_TRAMPOLINE
> + /* Fixup trampoline */
> addq %rbp, trampoline_level4_pgt + 0(%rip)
> addq %rbp, trampoline_level4_pgt + (511*8)(%rip)
> -#endif
>
> /* Due to ENTRY(), sometimes the empty space gets filled with
> * zeros. Better take a jmp than relying on empty space being
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index d3cfe26..994ea20 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -935,7 +935,7 @@ void __init setup_arch(char **cmdline_p)
> printk(KERN_DEBUG "initial memory mapped : 0 - %08lx\n",
> max_pfn_mapped<<PAGE_SHIFT);
>
> - reserve_trampoline_memory();
> + setup_trampolines();
>
> #ifdef CONFIG_ACPI_SLEEP
> /*
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 08776a9..5452733 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -788,7 +788,7 @@ do_rest:
> stack_start = c_idle.idle->thread.sp;
>
> /* start_ip had better be page-aligned! */
> - start_ip = setup_trampoline();
> + start_ip = trampoline_address();
>
> /* So we see what's up */
> announce_cpu(cpu, apicid);
> @@ -798,6 +798,8 @@ do_rest:
> * the targeted processor.
> */
>
> + printk(KERN_DEBUG "smpboot cpu %d: start_ip = %lx\n", cpu, start_ip);
> +
> atomic_set(&init_deasserted, 0);
>
> if (get_uv_system_type() != UV_NON_UNIQUE_APIC) {
> @@ -851,8 +853,8 @@ do_rest:
> pr_debug("CPU%d: has booted.\n", cpu);
> else {
> boot_error = 1;
> - if (*((volatile unsigned char *)trampoline_base)
> - == 0xA5)
> + if (*(volatile u32 *)TRAMPOLINE_SYM(trampoline_status)
> + == 0xA5A5A5A5)
> /* trampoline started but...? */
> pr_err("CPU%d: Stuck ??\n", cpu);
> else
> @@ -878,7 +880,7 @@ do_rest:
> }
>
> /* mark "stuck" area as not stuck */
> - *((volatile unsigned long *)trampoline_base) = 0;
> + *(volatile u32 *)TRAMPOLINE_SYM(trampoline_status) = 0;
>
> if (get_uv_system_type() != UV_NON_UNIQUE_APIC) {
> /*
> diff --git a/arch/x86/kernel/trampoline.c b/arch/x86/kernel/trampoline.c
> index a375616..a91ae77 100644
> --- a/arch/x86/kernel/trampoline.c
> +++ b/arch/x86/kernel/trampoline.c
> @@ -2,39 +2,41 @@
> #include <linux/memblock.h>
>
> #include <asm/trampoline.h>
> +#include <asm/cacheflush.h>
> #include <asm/pgtable.h>
>
> -#if defined(CONFIG_X86_64) && defined(CONFIG_ACPI_SLEEP)
> -#define __trampinit
> -#define __trampinitdata
> -#else
> -#define __trampinit __cpuinit
> -#define __trampinitdata __cpuinitdata
> -#endif
> +unsigned char *x86_trampoline_base;
>
> -/* ready for x86_64 and x86 */
> -unsigned char *__trampinitdata trampoline_base;
> -
> -void __init reserve_trampoline_memory(void)
> +void __init setup_trampolines(void)
> {
> phys_addr_t mem;
> + size_t size = PAGE_ALIGN(x86_trampoline_end - x86_trampoline_start);
>
> /* Has to be in very low memory so we can execute real-mode AP code. */
> - mem = memblock_find_in_range(0, 1<<20, TRAMPOLINE_SIZE, PAGE_SIZE);
> + mem = memblock_find_in_range(0, 1<<20, size, PAGE_SIZE);
> if (mem == MEMBLOCK_ERROR)
> panic("Cannot allocate trampoline\n");
>
> - trampoline_base = __va(mem);
> - memblock_x86_reserve_range(mem, mem + TRAMPOLINE_SIZE, "TRAMPOLINE");
> + x86_trampoline_base = __va(mem);
> + memblock_x86_reserve_range(mem, mem + size, "TRAMPOLINE");
> +
> + printk(KERN_DEBUG "Base memory trampoline at [%p] %llx size %zu\n",
> + x86_trampoline_base, (unsigned long long)mem, size);
> +
> + memcpy(x86_trampoline_base, x86_trampoline_start, size);
> }
>
> /*
> - * Currently trivial. Write the real->protected mode
> - * bootstrap into the page concerned. The caller
> - * has made sure it's suitably aligned.
> + * setup_trampolines() gets called very early, to guarantee the
> + * availability of low memory. This is before the proper kernel page
> + * tables are set up, so we cannot set page permissions in that
> + * function. Thus, we use an arch_initcall instead.
> */
> -unsigned long __trampinit setup_trampoline(void)
> +static int __init configure_trampolines(void)
> {
> - memcpy(trampoline_base, trampoline_data, TRAMPOLINE_SIZE);
> - return virt_to_phys(trampoline_base);
> + size_t size = PAGE_ALIGN(x86_trampoline_end - x86_trampoline_start);
> +
> + set_memory_x((unsigned long)x86_trampoline_base, size >> PAGE_SHIFT);
> + return 0;
> }
> +arch_initcall(configure_trampolines);
> diff --git a/arch/x86/kernel/trampoline_32.S b/arch/x86/kernel/trampoline_32.S
> index 8508237..451c0a7 100644
> --- a/arch/x86/kernel/trampoline_32.S
> +++ b/arch/x86/kernel/trampoline_32.S
> @@ -32,9 +32,11 @@
> #include <asm/segment.h>
> #include <asm/page_types.h>
>
> -/* We can free up trampoline after bootup if cpu hotplug is not supported. */
> -__CPUINITRODATA
> -.code16
> +#ifdef CONFIG_SMP
> +
> + .section ".x86_trampoline","a"
> + .balign PAGE_SIZE
> + .code16
>
> ENTRY(trampoline_data)
> r_base = .
> @@ -44,7 +46,7 @@ r_base = .
>
> cli # We should be safe anyway
>
> - movl $0xA5A5A5A5, trampoline_data - r_base
> + movl $0xA5A5A5A5, trampoline_status - r_base
> # write marker for master knows we're running
>
> /* GDT tables in non default location kernel can be beyond 16MB and
> @@ -72,5 +74,10 @@ boot_idt_descr:
> .word 0 # idt limit = 0
> .long 0 # idt base = 0L
>
> +ENTRY(trampoline_status)
> + .long 0
> +
> .globl trampoline_end
> trampoline_end:
> +
> +#endif /* CONFIG_SMP */
> diff --git a/arch/x86/kernel/trampoline_64.S b/arch/x86/kernel/trampoline_64.S
> index 075d130..49c77a6 100644
> --- a/arch/x86/kernel/trampoline_64.S
> +++ b/arch/x86/kernel/trampoline_64.S
> @@ -32,13 +32,9 @@
> #include <asm/segment.h>
> #include <asm/processor-flags.h>
>
> -#ifdef CONFIG_ACPI_SLEEP
> -.section .rodata, "a", @progbits
> -#else
> -/* We can free up the trampoline after bootup if cpu hotplug is not supported. */
> -__CPUINITRODATA
> -#endif
> -.code16
> + .section ".x86_trampoline","a"
> + .balign PAGE_SIZE
> + .code16
>
> ENTRY(trampoline_data)
> r_base = .
> @@ -50,7 +46,7 @@ r_base = .
> mov %ax, %ss
>
>
> - movl $0xA5A5A5A5, trampoline_data - r_base
> + movl $0xA5A5A5A5, trampoline_status - r_base
> # write marker for master knows we're running
>
> # Setup stack
> @@ -64,10 +60,13 @@ r_base = .
> movzx %ax, %esi # Find the 32bit trampoline location
> shll $4, %esi
>
> - # Fixup the vectors
> - addl %esi, startup_32_vector - r_base
> - addl %esi, startup_64_vector - r_base
> - addl %esi, tgdt + 2 - r_base # Fixup the gdt pointer
> + # Fixup the absolute vectors
> + leal (startup_32 - r_base)(%esi), %eax
> + movl %eax, startup_32_vector - r_base
> + leal (startup_64 - r_base)(%esi), %eax
> + movl %eax, startup_64_vector - r_base
> + leal (tgdt - r_base)(%esi), %eax
> + movl %eax, (tgdt + 2 - r_base)
>
> /*
> * GDT tables in non default location kernel can be beyond 16MB and
> @@ -129,6 +128,7 @@ no_longmode:
> jmp no_longmode
> #include "verify_cpu.S"
>
> + .balign 4
> # Careful these need to be in the same 64K segment as the above;
> tidt:
> .word 0 # idt limit = 0
> @@ -156,6 +156,12 @@ startup_64_vector:
> .long startup_64 - r_base
> .word __KERNEL_CS, 0
>
> + .balign 4
> +fixup_base:
> + .long 0
fixup_base looks unused.
> +ENTRY(trampoline_status)
> + .long 0
> +
> trampoline_stack:
> .org 0x1000
> trampoline_stack_end:
> diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
> index bf47007..cb2c506 100644
> --- a/arch/x86/kernel/vmlinux.lds.S
> +++ b/arch/x86/kernel/vmlinux.lds.S
> @@ -240,6 +240,18 @@ SECTIONS
>
> INIT_DATA_SECTION(16)
>
> + /*
> + * Code and data for a variety of lowlevel trampolines, to be
> + * copied into base memory (< 1 MiB) during initialization.
> + * Since it is copied early, the main copy can be discarded
> + * afterwards.
> + */
> + .x86_trampoline : AT(ADDR(.x86_trampoline) - LOAD_OFFSET) {
> + x86_trampoline_start = .;
> + *(.x86_trampoline)
> + x86_trampoline_end = .;
> + }
> +
> .x86_cpu_dev.init : AT(ADDR(.x86_cpu_dev.init) - LOAD_OFFSET) {
> __x86_cpu_dev_start = .;
> *(.x86_cpu_dev.init)
> @@ -291,6 +303,7 @@ SECTIONS
> *(.iommu_table)
> __iommu_table_end = .;
> }
> +
> . = ALIGN(8);
> /*
> * .exit.text is discard at runtime, not link time, to deal with
> --
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>
--
Brian Gerst
--
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