From ac71d12c990526b01ef6cfe50907ef8530a30331 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Mon, 8 May 2006 15:17:28 +0200 Subject: [PATCH] [PATCH] x86_64: Avoid EBDA area in early boot allocator Based on analysis&patch from Robert Hentosch Observed on a Dell PE6850 with 16GB The problem occurs very early on, when the kernel allocates space for the temporary memory map called bootmap. The bootmap overlaps the EBDA region. EBDA region is not historically reserved in the e820 mapping. When the bootmap is freed it marks the EBDA region as usable. If you notice in setup.c there is already code to work around the EBDA in reserve_ebda_region(), this check however occurs after the bootmap is allocated and doesn't prevent the bootmap from using this range. AK: I redid the original patch. Thanks also to Jan Beulich for spotting some mistakes. Cc: Robert_Hentosch@dell.com Cc: jbeulich@novell.com Signed-off-by: Andi Kleen Signed-off-by: Linus Torvalds --- arch/x86_64/kernel/e820.c | 6 ++++++ arch/x86_64/kernel/setup.c | 30 ++++++++++++++++++++++-------- include/asm-x86_64/e820.h | 2 ++ 3 files changed, 30 insertions(+), 8 deletions(-) diff --git a/arch/x86_64/kernel/e820.c b/arch/x86_64/kernel/e820.c index 62776c07cf..222b5b46d2 100644 --- a/arch/x86_64/kernel/e820.c +++ b/arch/x86_64/kernel/e820.c @@ -76,6 +76,12 @@ static inline int bad_addr(unsigned long *addrp, unsigned long size) *addrp = __pa_symbol(&_end); return 1; } + + if (last >= ebda_addr && addr < ebda_addr + ebda_size) { + *addrp = ebda_addr + ebda_size; + return 1; + } + /* XXX ramdisk image here? */ return 0; } diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c index ebc3c33b1c..f0870bef24 100644 --- a/arch/x86_64/kernel/setup.c +++ b/arch/x86_64/kernel/setup.c @@ -571,17 +571,28 @@ static inline void copy_edd(void) #endif #define EBDA_ADDR_POINTER 0x40E -static void __init reserve_ebda_region(void) + +unsigned __initdata ebda_addr; +unsigned __initdata ebda_size; + +static void discover_ebda(void) { - unsigned int addr; - /** + /* * there is a real-mode segmented pointer pointing to the * 4K EBDA area at 0x40E */ - addr = *(unsigned short *)phys_to_virt(EBDA_ADDR_POINTER); - addr <<= 4; - if (addr) - reserve_bootmem_generic(addr, PAGE_SIZE); + ebda_addr = *(unsigned short *)EBDA_ADDR_POINTER; + ebda_addr <<= 4; + + ebda_size = *(unsigned short *)(unsigned long)ebda_addr; + + /* Round EBDA up to pages */ + if (ebda_size == 0) + ebda_size = 1; + ebda_size <<= 10; + ebda_size = round_up(ebda_size + (ebda_addr & ~PAGE_MASK), PAGE_SIZE); + if (ebda_size > 64*1024) + ebda_size = 64*1024; } void __init setup_arch(char **cmdline_p) @@ -627,6 +638,8 @@ void __init setup_arch(char **cmdline_p) check_efer(); + discover_ebda(); + init_memory_mapping(0, (end_pfn_map << PAGE_SHIFT)); dmi_scan_machine(); @@ -669,7 +682,8 @@ void __init setup_arch(char **cmdline_p) reserve_bootmem_generic(0, PAGE_SIZE); /* reserve ebda region */ - reserve_ebda_region(); + if (ebda_addr) + reserve_bootmem_generic(ebda_addr, ebda_size); #ifdef CONFIG_SMP /* diff --git a/include/asm-x86_64/e820.h b/include/asm-x86_64/e820.h index 93b51df516..670a3388e7 100644 --- a/include/asm-x86_64/e820.h +++ b/include/asm-x86_64/e820.h @@ -59,6 +59,8 @@ extern void __init parse_memopt(char *p, char **end); extern void __init parse_memmapopt(char *p, char **end); extern struct e820map e820; + +extern unsigned ebda_addr, ebda_size; #endif/*!__ASSEMBLY__*/ #endif/*__E820_HEADER*/ -- 2.39.5