From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52304) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a3M3z-0000Y0-Rr for qemu-devel@nongnu.org; Mon, 30 Nov 2015 05:52:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1a3M3v-0007I9-Q8 for qemu-devel@nongnu.org; Mon, 30 Nov 2015 05:52:07 -0500 Received: from e06smtp08.uk.ibm.com ([195.75.94.104]:45324) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1a3M3v-0007Hr-GD for qemu-devel@nongnu.org; Mon, 30 Nov 2015 05:52:03 -0500 Received: from localhost by e06smtp08.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 30 Nov 2015 10:52:02 -0000 Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by d06dlp01.portsmouth.uk.ibm.com (Postfix) with ESMTP id B270B17D805D for ; Mon, 30 Nov 2015 10:52:27 +0000 (GMT) Received: from d06av07.portsmouth.uk.ibm.com (d06av07.portsmouth.uk.ibm.com [9.149.37.248]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id tAUApxBd10420500 for ; Mon, 30 Nov 2015 10:52:00 GMT Received: from d06av07.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av07.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id tAUApxZp017430 for ; Mon, 30 Nov 2015 03:51:59 -0700 From: Greg Kurz Date: Mon, 30 Nov 2015 11:51:57 +0100 Message-ID: <20151130105044.12269.21261.stgit@bahia.huguette.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] [PATCH] mmap-alloc: use same backend for all mappings List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini , "Michael S. Tsirkin" Cc: qemu-devel@nongnu.org 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 due to a limitation on ppc64 that requires MAP_FIXED mappings to have the same page size as other mappings already present in the same "slice" of virtual address space (Cc'ing Ben for details). This is exactly what happens when calling mmap() above: first one uses native host page size (64k) and second one uses huge page size (16M). To be sure we always have the same page size, let's use the same backend for both calls to mmap(): this is enough to fix the ppc64 issue. This has no effect on RAM based mappings. Signed-off-by: Greg Kurz --- This is a bug fix for 2.5 util/mmap-alloc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c index c37acbe58ede..0ff221dd94f4 100644 --- a/util/mmap-alloc.c +++ b/util/mmap-alloc.c @@ -21,7 +21,8 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared) * space, even if size is already aligned. */ size_t total = size + align; - void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + void *ptr = mmap(0, total, PROT_NONE, + (fd == -1 ? MAP_ANONYMOUS : 0) | MAP_PRIVATE, fd, 0); size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr; void *ptr1;