From 7197fb4058bcb68986bae2bb2c04d6370f3e7218 Mon Sep 17 00:00:00 2001 From: Michael S. Tsirkin Date: Wed, 2 Dec 2015 21:14:12 +0200 Subject: util/mmap-alloc: fix hugetlb support on ppc64 Since commit 8561c9244ddf1122d "exec: allocate PROT_NONE pages on top of RAM", it is no longer possible to back guest RAM with hugepages on ppc64 hosts: mmap(NULL, 285212672, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x3fff57000000 mmap(0x3fff57000000, 268435456, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 19, 0) = -1 EBUSY (Device or resource busy) This is because on ppc64, Linux fixes a page size for a virtual address at mmap time, so we can't switch a range of memory from anonymous small pages to hugetlbs with MAP_FIXED. See commit d0f13e3c20b6fb73ccb467bdca97fa7cf5a574cd ("[POWERPC] Introduce address space "slices"") in Linux history for the details. Detect this and create the PROT_NONE mapping using the same fd. Naturally, this makes the guard page bigger with hugetlbfs. Based on patch by Greg Kurz. Acked-by: Rik van Riel Reviewed-by: Greg Kurz Tested-by: Greg Kurz Signed-off-by: Michael S. Tsirkin --- include/qemu/mmap-alloc.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h index 56388e689b..0899b2f01e 100644 --- a/include/qemu/mmap-alloc.h +++ b/include/qemu/mmap-alloc.h @@ -3,6 +3,8 @@ #include "qemu-common.h" +size_t qemu_fd_getpagesize(int fd); + void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared); void qemu_ram_munmap(void *ptr, size_t size); -- cgit v1.2.3-55-g7522