From 077b04c0350e1bc20a41b06dad49a3e2a72ca8c8 Mon Sep 17 00:00:00 2001 From: Keir Fraser Date: Wed, 21 Jul 2010 08:43:35 +0100 Subject: [PATCH] x86: New boot option availmem= to limit usable system RAM. Unlike mem=, this specifies the limit on usable RAM, rather than a limit on maximum physical address of RAM. Original patch by Sarina Canelake Signed-off-by: Keir Fraser --- xen/arch/x86/e820.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/xen/arch/x86/e820.c b/xen/arch/x86/e820.c index fb76b5c51a..a9276cd17c 100644 --- a/xen/arch/x86/e820.c +++ b/xen/arch/x86/e820.c @@ -10,10 +10,20 @@ #include #include -/* opt_mem: Limit of physical RAM. Any RAM beyond this point is ignored. */ +/* + * opt_mem: Limit maximum address of physical RAM. + * Any RAM beyond this address limit is ignored. + */ static unsigned long long __initdata opt_mem; size_param("mem", opt_mem); +/* + * opt_availmem: Limit maximum usable amount of physical RAM. + * Any RAM beyond this limited amount is ignored. + */ +static unsigned long long __initdata opt_availmem; +size_param("availmem", opt_availmem); + /* opt_nomtrr_check: Don't clip ram to highest cacheable MTRR. */ static int __initdata e820_mtrr_clip = -1; boolean_param("e820-mtrr-clip", e820_mtrr_clip); @@ -503,7 +513,8 @@ static void __init reserve_dmi_region(void) static void __init machine_specific_memory_setup( struct e820entry *raw, int *raw_nr) { - uint64_t top_of_ram; + uint64_t top_of_ram, size; + int i; char nr = (char)*raw_nr; sanitize_e820_map(raw, &nr); @@ -513,6 +524,17 @@ static void __init machine_specific_memory_setup( if ( opt_mem ) clip_to_limit(opt_mem, NULL); + if ( opt_availmem ) + { + for ( i = size = 0; (i < e820.nr_map) && (size <= opt_availmem); i++ ) + if ( e820.map[i].type == E820_RAM ) + size += e820.map[i].size; + if ( size > opt_availmem ) + clip_to_limit( + e820.map[i-1].addr + e820.map[i-1].size - (size-opt_availmem), + NULL); + } + #ifdef __i386__ clip_to_limit((1ULL << 30) * MACHPHYS_MBYTES, "Only the first %lu GB of the physical memory map " -- 2.30.2