From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:49169) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gjnac-0001e6-LH for qemu-devel@nongnu.org; Wed, 16 Jan 2019 10:58:51 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gjnab-0002Gb-14 for qemu-devel@nongnu.org; Wed, 16 Jan 2019 10:58:49 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33574) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gjnaa-0002Ej-Oe for qemu-devel@nongnu.org; Wed, 16 Jan 2019 10:58:48 -0500 Date: Wed, 16 Jan 2019 10:58:44 -0500 From: "Michael S. Tsirkin" Message-ID: <20190116104105-mutt-send-email-mst@kernel.org> References: <64bea1ff5f80647cc4592ee94d399d647bdd9862.1547624239.git.yi.z.zhang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <64bea1ff5f80647cc4592ee94d399d647bdd9862.1547624239.git.yi.z.zhang@linux.intel.com> Subject: Re: [Qemu-devel] [PATCH V9 4/6] util/mmap-alloc: support MAP_SYNC in qemu_ram_mmap() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Zhang Yi Cc: xiaoguangrong.eric@gmail.com, stefanha@redhat.com, pbonzini@redhat.com, pagupta@redhat.com, yu.c.zhang@linux.intel.com, ehabkost@redhat.com, qemu-devel@nongnu.org, imammedo@redhat.com, dan.j.williams@intel.com On Wed, Jan 16, 2019 at 04:10:58PM +0800, Zhang Yi wrote: > When a file supporting DAX is used as vNVDIMM backend, mmap it with > MAP_SYNC flag in addition which can ensure file system metadata > synced in each guest writes to the backend file, without other QEMU > actions (e.g., periodic fsync() by QEMU). > > Signed-off-by: Haozhong Zhang > Signed-off-by: Zhang Yi > --- > include/qemu/mmap-alloc.h | 1 + > include/qemu/osdep.h | 16 ++++++++++++++++ > util/mmap-alloc.c | 7 ++++++- > 3 files changed, 23 insertions(+), 1 deletion(-) > > diff --git a/include/qemu/mmap-alloc.h b/include/qemu/mmap-alloc.h > index 6fe6ed4..a95d91c 100644 > --- a/include/qemu/mmap-alloc.h > +++ b/include/qemu/mmap-alloc.h > @@ -18,6 +18,7 @@ size_t qemu_mempath_getpagesize(const char *mem_path); > * @flags: specifies additional properties of the mapping, which can be one or > * bit-or of following values > * - RAM_SHARED: mmap with MAP_SHARED flag > + * - RAM_PMEM: mmap with MAP_SYNC flag > * Other bits are ignored. > * > * Return: > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h > index 457d24e..27a6bfe 100644 > --- a/include/qemu/osdep.h > +++ b/include/qemu/osdep.h > @@ -419,6 +419,22 @@ void qemu_anon_ram_free(void *ptr, size_t size); > # define QEMU_VMALLOC_ALIGN getpagesize() > #endif > > +/* > + * MAP_SHARED_VALIDATE and MAP_SYNC are introduced in Linux kernel > + * 4.15, so they may not be defined when compiling on older kernels. > + */ > +#ifdef CONFIG_LINUX > + > +#include I suspect this is a wrong way to pull in this header. You are normally supposed to use #include but see below. > + > +#ifndef MAP_SYNC > +#define MAP_SYNC 0x0 > +#endif Oh that's bad. So if you run with a new kernel but your installed headers are old, you get MAP_SYNC 0 and no persistence transparently with no warning. > + > +#else /* !CONFIG_LINUX */ > +#define MAP_SYNC 0x0 > +#endif /* CONFIG_LINUX */ > + > #ifdef CONFIG_POSIX > struct qemu_signalfd_siginfo { > uint32_t ssi_signo; /* Signal number */ > diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c > index 8f0a740..cba961c 100644 > --- a/util/mmap-alloc.c > +++ b/util/mmap-alloc.c > @@ -99,6 +99,8 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, uint32_t flags) > void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); > #endif > bool shared = flags & RAM_SHARED; > + bool is_pmem = flags & RAM_PMEM; > + int mmap_xflags = 0; > size_t offset; > void *ptr1; > > @@ -109,12 +111,15 @@ void *qemu_ram_mmap(int fd, size_t size, size_t align, uint32_t flags) > assert(is_power_of_2(align)); > /* Always align to host page size */ > assert(align >= getpagesize()); > + if (shared && is_pmem) { > + mmap_xflags |= MAP_SYNC; > + } > > offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr; > ptr1 = mmap(ptr + offset, size, PROT_READ | PROT_WRITE, > MAP_FIXED | > (fd == -1 ? MAP_ANONYMOUS : 0) | > - (shared ? MAP_SHARED : MAP_PRIVATE), > + (shared ? MAP_SHARED : MAP_PRIVATE) | mmap_xflags, > fd, 0); > if (ptr1 == MAP_FAILED) { > munmap(ptr, total); > -- > 2.7.4