diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.rst | 7 | ||||
| -rw-r--r-- | lib/bitmap.c | 22 |
2 files changed, 24 insertions, 5 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst index 1132796a8d96..d6e3f67953a7 100644 --- a/Documentation/admin-guide/kernel-parameters.rst +++ b/Documentation/admin-guide/kernel-parameters.rst @@ -68,6 +68,13 @@ For example one can add to the command line following parameter: where the final item represents CPUs 100,101,125,126,150,151,... +The value "N" can be used to represent the numerically last CPU on the system, +i.e "foo_cpus=16-N" would be equivalent to "16-31" on a 32 core system. + +Keep in mind that "N" is dynamic, so if system changes cause the bitmap width +to change, such as less cores in the CPU list, then N and any ranges using N +will also change. Use the same on a small 4 core system, and "16-N" becomes +"16-3" and now the same boot input will be flagged as invalid (start > end). This document may not be entirely up to date and comprehensive. The command diff --git a/lib/bitmap.c b/lib/bitmap.c index 833f152a2c43..9f4626a4c95f 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -519,11 +519,17 @@ static int bitmap_check_region(const struct region *r) return 0; } -static const char *bitmap_getnum(const char *str, unsigned int *num) +static const char *bitmap_getnum(const char *str, unsigned int *num, + unsigned int lastbit) { unsigned long long n; unsigned int len; + if (str[0] == 'N') { + *num = lastbit; + return str + 1; + } + len = _parse_integer(str, 10, &n); if (!len) return ERR_PTR(-EINVAL); @@ -571,7 +577,9 @@ static const char *bitmap_find_region_reverse(const char *start, const char *end static const char *bitmap_parse_region(const char *str, struct region *r) { - str = bitmap_getnum(str, &r->start); + unsigned int lastbit = r->nbits - 1; + + str = bitmap_getnum(str, &r->start, lastbit); if (IS_ERR(str)) return str; @@ -581,7 +589,7 @@ static const char *bitmap_parse_region(const char *str, struct region *r) if (*str != '-') return ERR_PTR(-EINVAL); - str = bitmap_getnum(str + 1, &r->end); + str = bitmap_getnum(str + 1, &r->end, lastbit); if (IS_ERR(str)) return str; @@ -591,14 +599,14 @@ static const char *bitmap_parse_region(const char *str, struct region *r) if (*str != ':') return ERR_PTR(-EINVAL); - str = bitmap_getnum(str + 1, &r->off); + str = bitmap_getnum(str + 1, &r->off, lastbit); if (IS_ERR(str)) return str; if (*str != '/') return ERR_PTR(-EINVAL); - return bitmap_getnum(str + 1, &r->group_len); + return bitmap_getnum(str + 1, &r->group_len, lastbit); no_end: r->end = r->start; @@ -625,6 +633,10 @@ no_pattern: * From each group will be used only defined amount of bits. * Syntax: range:used_size/group_size * Example: 0-1023:2/256 ==> 0,1,256,257,512,513,768,769 + * The value 'N' can be used as a dynamically substituted token for the + * maximum allowed value; i.e (nmaskbits - 1). Keep in mind that it is + * dynamic, so if system changes cause the bitmap width to change, such + * as more cores in a CPU list, then any ranges using N will also change. * * Returns: 0 on success, -errno on invalid input strings. Error values: * |