kexec: align crash_notes allocation to make it be inside one physical page

Port of mainline commit bbb78b8f3

Orabug: 25071982

Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
(cherry picked from commit 45cbd27626d17d485ca0718b28add12513690921)
Signed-off-by: Allen Pais <allen.pais@oracle.com>

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 7a36fdcca5bfb064a6709021782c98bd2a6de179..b4ac99c58ef41849fe580e58489a26d1fbcf10e3 100644 (file)
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1609,7 +1609,28 @@ void crash_save_cpu(struct pt_regs *regs, int cpu)
 static int __init crash_notes_memory_init(void)
 {
        /* Allocate memory for saving cpu registers. */
-       crash_notes = alloc_percpu(note_buf_t);
+       size_t size, align;
+
+       /*
+        * crash_notes could be allocated across 2 vmalloc pages when percpu
+        * is vmalloc based . vmalloc doesn't guarantee 2 continuous vmalloc
+        * pages are also on 2 continuous physical pages. In this case the
+        * 2nd part of crash_notes in 2nd page could be lost since only the
+        * starting address and size of crash_notes are exported through sysfs.
+        * Here round up the size of crash_notes to the nearest power of two
+        * and pass it to __alloc_percpu as align value. This can make sure
+        * crash_notes is allocated inside one physical page.
+        */
+       size = sizeof(note_buf_t);
+       align = min(roundup_pow_of_two(sizeof(note_buf_t)), PAGE_SIZE);
+
+       /*
+        * Break compile if size is bigger than PAGE_SIZE since crash_notes
+        * definitely will be in 2 pages with that.
+        */
+       BUILD_BUG_ON(size > PAGE_SIZE);
+
+       crash_notes = __alloc_percpu(size, align);
        if (!crash_notes) {
                pr_warn("Kexec: Memory allocation for saving cpu register states failed\n");
                return -ENOMEM;