From: Li Zhe <lizhe.67@xxxxxxxxxxxxx> In current kernel we can use memmap=nn[KMG]$ss[KMG] to reserve an area of memory for another use from kernel. We have to determine it's start addr and length. In our scenario, we need reserve or alloc large continous memory like 256M in machine which have different memory specification at just boot phase for a user land process. And these memorys will not be freed to system before system reboot. It is a hard work for us to reserve memory with same length from machine with different memory specification, because we have to determine the start addr of the reserved memory for each type of machine. This patch introduce a cmdline parameter "memmap=nn[KMG]$" to make this work easy. It is an extension of "memmap=nn[KMG]$ss[KMG]". We don't need to input the start addr. Kernel will reserve a suitable area of memory and we can get the area from /proc/iomem with the key word "Memmap Alloc". Notice that we need "$" in our cmdline parameter or it will be confused with memmap=nn[KMG]@ss[KMG]. Signed-off-by: Li Zhe <lizhe.67@xxxxxxxxxxxxx> --- .../admin-guide/kernel-parameters.txt | 7 ++ arch/x86/kernel/e820.c | 64 ++++++++++++++++++- 2 files changed, 69 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2522b11e593f..b88df1e61d48 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3022,6 +3022,13 @@ memmap=64K$0x18690000 or memmap=0x10000$0x18690000 + [KNL, X86] If @ss[KMG] is omitted, kernel will reserve a + suitable area of memory for us. We can find the area from + /proc/iomem with key word "Memmap Alloc". + Example: Exclude memory with size 0x10000 + memmap=64K$ + or + memmap=0x10000$ Some bootloaders may need an escape character before '$', like Grub2, otherwise '$' and the following number will be eaten. diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c index f267205f2d5a..241d41ec870f 100644 --- a/arch/x86/kernel/e820.c +++ b/arch/x86/kernel/e820.c @@ -942,8 +942,18 @@ static int __init parse_memmap_one(char *p) start_at = memparse(p+1, &p); e820__range_add(start_at, mem_size, E820_TYPE_ACPI); } else if (*p == '$') { - start_at = memparse(p+1, &p); - e820__range_add(start_at, mem_size, E820_TYPE_RESERVED); + if (*(p+1) == '\0') { + /* + * In the case we just want to reserve memory with size + * 'mem_size' and don't care where it start, we get '\0' + * here. + */ + p++; + } else { + /* We determine the start and size of the reserved memory */ + start_at = memparse(p+1, &p); + e820__range_add(start_at, mem_size, E820_TYPE_RESERVED); + } } else if (*p == '!') { start_at = memparse(p+1, &p); e820__range_add(start_at, mem_size, E820_TYPE_PRAM); @@ -972,6 +982,40 @@ static int __init parse_memmap_one(char *p) return *p == '\0' ? 0 : -EINVAL; } +static int __init setup_memmap_random(char *p) +{ + char *oldp; + struct resource *res; + u64 start_at, mem_size; + + if (!p) + return -EINVAL; + oldp = p; + mem_size = memparse(p, &p); + if (p == oldp) + return -EINVAL; + + if (*p == '$') { + if (*(p+1) != '\0') + return 0; /* no need to deal with */ + start_at = memblock_phys_alloc(mem_size, SMP_CACHE_BYTES); + if (start_at == 0) + return -ENOMEM; + res = memblock_alloc(sizeof(struct resource), SMP_CACHE_BYTES); + if (res == NULL) { + memblock_phys_free(start_at, mem_size); + return -ENOMEM; + } + res->start = start_at; + res->end = start_at + mem_size - 1; + res->name = "Memmap Alloc"; + res->flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM, + res->desc = IORES_DESC_RESERVED; + insert_resource(&iomem_resource, res); + } + return 0; +} + static int __init parse_memmap_opt(char *str) { while (str) { @@ -988,6 +1032,22 @@ static int __init parse_memmap_opt(char *str) } early_param("memmap", parse_memmap_opt); +static int __init setup_memmap_opt(char *str) +{ + while (str) { + char *k = strchr(str, ','); + + if (k) + *k++ = 0; + + setup_memmap_random(str); + str = k; + } + + return 0; +} +__setup("memmap=", setup_memmap_opt); + /* * Reserve all entries from the bootloader's extensible data nodes list, * because if present we are going to use it later on to fetch e820 -- 2.20.1