From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:54956) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gmK4X-0004xW-5E for qemu-devel@nongnu.org; Wed, 23 Jan 2019 10:04:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gmK4V-0004PU-Mx for qemu-devel@nongnu.org; Wed, 23 Jan 2019 10:04:09 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37206) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gmK4V-0004Nn-DL for qemu-devel@nongnu.org; Wed, 23 Jan 2019 10:04:07 -0500 Date: Wed, 23 Jan 2019 10:04:01 -0500 From: "Michael S. Tsirkin" Message-ID: <20190123100252-mutt-send-email-mst@kernel.org> References: <286542bc2f48b0dd6a657f363a8e933806cac92d.1548136274.git.yi.z.zhang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <286542bc2f48b0dd6a657f363a8e933806cac92d.1548136274.git.yi.z.zhang@linux.intel.com> Subject: Re: [Qemu-devel] [PATCH V10 2/4] 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, richardw.yang@linux.intel.com, ehabkost@redhat.com, qemu-devel@nongnu.org, imammedo@redhat.com, dan.j.williams@intel.com On Wed, Jan 23, 2019 at 10:59:45AM +0800, Zhang, Yi wrote: > From: Zhang Yi > > 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). > > Current, We have below different possible use cases: > > 1. pmem=on is set, shared=on is set, MAP_SYNC supported: > a: backend is a dax supporting file. > - MAP_SYNC will active. > b: backend is not a dax supporting file. > - mmap will result in an EOPNOTSUPP error. > > 2. The rest of cases: > - we will never pass the MAP_SYNC to mmap2 > > Signed-off-by: Haozhong Zhang > Signed-off-by: Zhang Yi > --- > include/qemu/mmap-alloc.h | 1 + > include/qemu/osdep.h | 21 +++++++++++++++++++++ > util/mmap-alloc.c | 7 ++++++- > 3 files changed, 28 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..3bcf155 100644 > --- a/include/qemu/osdep.h > +++ b/include/qemu/osdep.h > @@ -419,6 +419,27 @@ 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. > + */ I commented on this part in v7. That's a wrong way to handle compatibility. > +#ifdef CONFIG_LINUX > + > +#include > + > +#ifndef MAP_SYNC > +#define MAP_SYNC 0x0 > +#endif > + > +#ifndef MAP_SHARED_VALIDATE > +#define MAP_SHARED_VALIDATE 0x0 > +#endif > + > +#else /* !CONFIG_LINUX */ > +#define MAP_SYNC 0x0 > +#define MAP_SHARED_VALIDATE 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..a4ce9b5 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 | MAP_SHARED_VALIDATE); > + } > > 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