Messages in this thread Patch in this message | | | From | Feng Tang <> | Subject | [PATCH] x86, mm: Reserver some memory for bootmem allocator for NO_BOOTMEM | Date | Thu, 30 Aug 2018 17:03:19 +0800 |
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We hit a kernel panic when enabling earlycon for a platform, the call trace is:
panic+0xd2/0x220 __alloc_bootmem+0x31/0x34 spp_getpage+0x60/0x8a fill_pte+0x71/0x130 __set_pte_vaddr+0x1d/0x50 set_pte_vaddr+0x3c/0x60 __native_set_fixmap+0x23/0x30 native_set_fixmap+0x30/0x40 setup_earlycon+0x1e0/0x32f param_setup_earlycon+0x13/0x22 do_early_param+0x5b/0x90 parse_args+0x1f7/0x300 parse_early_options+0x24/0x28 parse_early_param+0x65/0x73 setup_arch+0x31e/0x9f1 start_kernel+0x58/0x44e
The root cause is that when CONFIG_NO_BOOTMEM=y, before e820__memblock_setup() is called there is no memory for bootmem to allocate, and any alloc_bootmem() in this time window will trigger a panic. Seems this is a known issue as already mentioned in arch/x86/kernel/setup.c: " /* after early param, so could get panic from serial */ memblock_x86_reserve_range_setup_data(); " By reserving some memory in the linker script, small memory request could be fulfilled by bootmem allocator. And this memory region is not wasted, but usable after kernel boot.
Signed-off-by: Feng Tang <feng.tang@intel.com> --- arch/x86/include/asm/sections.h | 5 +++++ arch/x86/kernel/setup.c | 12 +++++++++++- arch/x86/kernel/vmlinux.lds.S | 9 +++++++++ 3 files changed, 25 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h index 4a911a382ade..d568829510e4 100644 --- a/arch/x86/include/asm/sections.h +++ b/arch/x86/include/asm/sections.h @@ -9,6 +9,11 @@ extern char __brk_base[], __brk_limit[]; extern struct exception_table_entry __stop___ex_table[]; extern char __end_rodata_aligned[]; +#ifdef CONFIG_NO_BOOTMEM +extern char __bootmem_start[], __bootmem_end[]; +#endif + + #if defined(CONFIG_X86_64) extern char __end_rodata_hpage_align[]; extern char __entry_trampoline_start[], __entry_trampoline_end[]; diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index b4866badb235..a4e3d9ec1a83 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -829,6 +829,17 @@ void __init setup_arch(char **cmdline_p) */ memblock_reserve(0, PAGE_SIZE); +#ifdef CONFIG_NO_BOOTMEM + /* + * There is small time window till e820__memblock_setup() is + * called, in which __bootmem_alloc() has no available memory + * to allocate and will trigger panic. Adding this revered bootmem + * can alleviate the situation. + */ + memblock_add(__pa_symbol(__bootmem_start), + __bootmem_end - __bootmem_start); +#endif + early_reserve_initrd(); /* @@ -989,7 +1000,6 @@ void __init setup_arch(char **cmdline_p) x86_report_nx(); - /* after early param, so could get panic from serial */ memblock_x86_reserve_range_setup_data(); if (acpi_mps_check()) { diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 8bde0a419f86..fec1965d668f 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -367,6 +367,15 @@ SECTIONS __brk_limit = .; } +#ifdef CONFIG_NO_BOOTMEM + . = ALIGN(PAGE_SIZE); + .bootmem : AT(ADDR(.bootmem) - LOAD_OFFSET) { + __bootmem_start = .; + . += 128 * 1024; /* 128 KB for early boot mem */ + __bootmem_end = .; + } +#endif + . = ALIGN(PAGE_SIZE); /* keep VO_INIT_SIZE page aligned */ _end = .; -- 2.14.1
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