Add a bootparameter to reserve high linear address space for hypervisors. This is necessary to allow dynamically loaded hypervisor modules, which might not happen until userspace is already running, and also provides a useful tool to benchmark the performance impact of reduced lowmem address space. Signed-off-by: Zachary Amsden Signed-off-by: Chris Wright --- Documentation/kernel-parameters.txt | 5 +++++ arch/i386/kernel/setup.c | 19 +++++++++++++++++++ 2 files changed, 24 insertions(+) =================================================================== --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1357,6 +1357,11 @@ running once the system is up. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area + reservetop= [IA-32] + Format: nn[KMG] + Reserves a hole at the top of the kernel virtual + address space. + resume= [SWSUSP] Specify the partition device for software suspend =================================================================== --- a/arch/i386/kernel/setup.c +++ b/arch/i386/kernel/setup.c @@ -160,6 +160,12 @@ static char command_line[COMMAND_LINE_SI static char command_line[COMMAND_LINE_SIZE]; unsigned char __initdata boot_params[PARAM_SIZE]; + +static int __init setup_reservetop(char *s) +{ + return 1; +} +__setup("reservetop", setup_reservetop); static struct resource data_resource = { .name = "Kernel data", @@ -917,6 +923,19 @@ static void __init parse_cmdline_early ( else if (!memcmp(from, "vmalloc=", 8)) __VMALLOC_RESERVE = memparse(from+8, &from); + /* + * reservetop=size reserves a hole at the top of the kernel + * address space which a hypervisor can load into later. + * Needed for dynamically loaded hypervisors, so relocating + * the fixmap can be done before paging initialization. + * This hole must be a multiple of 4M. + */ + else if (!memcmp(from, "reservetop=", 11)) { + unsigned long reserve = memparse(from+11, &from); + reserve &= ~0x3fffff; + reserve_top_address(reserve); + } + next_char: c = *(from++); if (!c) -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/