From: Jan Beulich Date: Fri, 30 Sep 2022 07:55:34 +0000 (+0200) Subject: x86/NUMA: correct off-by-1 in node map size calculation X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=b1f4b45d02cac2bf704c2fcc61c70c3567cfaa5b;p=people%2Ftklengyel%2Fxen.git x86/NUMA: correct off-by-1 in node map size calculation extract_lsb_from_nodes() accumulates "memtop" from all PDXes one past the covered ranges. Hence the maximum address which can validly by used to index the node map is one below this value, and we may currently set up a node map with an unused (and never initialized) trailing entry. In boundary cases this may also mean we dynamically allocate a page when the static (64-entry) map would suffice. While there also correct the comment ahead of the function, for it to match the actual code: Linux commit 54413927f022 ("x86-64: x86_64-make-the-numa-hash-function-nodemap-allocation fix fix") removed the ORing in of the end address before we actually cloned their code. Signed-off-by: Jan Beulich Acked-by: Roger Pau Monné Reviewed-by: Wei Chen --- diff --git a/xen/arch/x86/numa.c b/xen/arch/x86/numa.c index 1bc82c60aa..4f742414b0 100644 --- a/xen/arch/x86/numa.c +++ b/xen/arch/x86/numa.c @@ -111,7 +111,7 @@ static int __init allocate_cachealigned_memnodemap(void) } /* - * The LSB of all start and end addresses in the node map is the value of the + * The LSB of all start addresses in the node map is the value of the * maximum possible shift. */ static int __init extract_lsb_from_nodes(const struct node *nodes, @@ -137,7 +137,7 @@ static int __init extract_lsb_from_nodes(const struct node *nodes, i = BITS_PER_LONG - 1; else i = find_first_bit(&bitfield, sizeof(unsigned long)*8); - memnodemapsize = (memtop >> i) + 1; + memnodemapsize = ((memtop - 1) >> i) + 1; return i; }