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Wed, 05 Feb 2020 19:56:19 +0000 Received: from b03ledav006.gho.boulder.ibm.com (b03ledav006.gho.boulder.ibm.com [9.17.130.237]) by b03cxnp07029.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 015JuISA46203296 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 5 Feb 2020 19:56:18 GMT Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4C0B8C6057; Wed, 5 Feb 2020 19:56:18 +0000 (GMT) Received: from b03ledav006.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2BBC2C6055; Wed, 5 Feb 2020 19:56:16 +0000 (GMT) Received: from kermit.br.ibm.com (unknown [9.85.196.245]) by b03ledav006.gho.boulder.ibm.com (Postfix) with ESMTPS; Wed, 5 Feb 2020 19:56:15 +0000 (GMT) Subject: Re: [PATCH v1 07/13] util/mmap-alloc: Factor out populating of memory to mmap_populate() To: David Hildenbrand , qemu-devel@nongnu.org References: <20200203183125.164879-1-david@redhat.com> <20200203183125.164879-8-david@redhat.com> From: =?UTF-8?Q?Murilo_Opsfelder_Ara=c3=bajo?= Organization: IBM Message-ID: Date: Wed, 5 Feb 2020 16:56:13 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200203183125.164879-8-david@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.572 definitions=2020-02-05_06:2020-02-04, 2020-02-05 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 mlxscore=0 spamscore=0 priorityscore=1501 mlxlogscore=999 phishscore=0 impostorscore=0 malwarescore=0 suspectscore=2 adultscore=0 lowpriorityscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002050151 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] X-Received-From: 148.163.156.1 X-Mailman-Approved-At: Wed, 05 Feb 2020 16:02:17 -0500 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: muriloo@linux.ibm.com Cc: Eduardo Habkost , "Michael S . Tsirkin" , Greg Kurz , "Dr . David Alan Gilbert" , Paolo Bonzini , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hello, David. On 2/3/20 3:31 PM, David Hildenbrand wrote: > We want to populate memory within a reserved memory region. Let's factor > that out. > > Cc: "Michael S. Tsirkin" > Cc: Greg Kurz > Cc: Murilo Opsfelder Araujo > Cc: Eduardo Habkost > Cc: "Dr. David Alan Gilbert" > Signed-off-by: David Hildenbrand > --- Acked-by: Murilo Opsfelder Araujo A minor comment below. > util/mmap-alloc.c | 89 +++++++++++++++++++++++++---------------------- > 1 file changed, 47 insertions(+), 42 deletions(-) > > diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c > index 43a26f38a8..f043ccb0ab 100644 > --- a/util/mmap-alloc.c > +++ b/util/mmap-alloc.c > @@ -114,6 +114,50 @@ static void *mmap_reserve(size_t size, int fd) > return mmap(0, size, PROT_NONE, flags, fd, 0); > } > > +/* > + * Populate memory in a reserved region from the given fd (if any). > + */ > +static void *mmap_populate(void *ptr, size_t size, int fd, bool shared, > + bool is_pmem) > +{ > + int map_sync_flags = 0; > + int flags = MAP_FIXED; > + void *new_ptr; Do you think another name would be welcome here, e.g.: "populated_ptr" or "populated_memptr" or just "populated"? > + > + flags |= fd == -1 ? MAP_ANONYMOUS : 0; > + flags |= shared ? MAP_SHARED : MAP_PRIVATE; > + if (shared && is_pmem) { > + map_sync_flags = MAP_SYNC | MAP_SHARED_VALIDATE; > + } > + > + new_ptr = mmap(ptr, size, PROT_READ | PROT_WRITE, flags | map_sync_flags, > + fd, 0); > + if (new_ptr == MAP_FAILED && map_sync_flags) { > + if (errno == ENOTSUP) { > + char *proc_link = g_strdup_printf("/proc/self/fd/%d", fd); > + char *file_name = g_malloc0(PATH_MAX); > + int len = readlink(proc_link, file_name, PATH_MAX - 1); > + > + if (len < 0) { > + len = 0; > + } > + file_name[len] = '\0'; > + fprintf(stderr, "Warning: requesting persistence across crashes " > + "for backend file %s failed. Proceeding without " > + "persistence, data might become corrupted in case of host " > + "crash.\n", file_name); > + g_free(proc_link); > + g_free(file_name); > + } > + /* > + * If mmap failed with MAP_SHARED_VALIDATE | MAP_SYNC, we will try > + * again without these flags to handle backwards compatibility. > + */ > + new_ptr = mmap(ptr, size, PROT_READ | PROT_WRITE, flags, fd, 0); > + } > + return new_ptr; > +} > + > static inline size_t mmap_pagesize(int fd) > { > #if defined(__powerpc64__) && defined(__linux__) > @@ -131,12 +175,8 @@ void *qemu_ram_mmap(int fd, > bool is_pmem) > { > const size_t pagesize = mmap_pagesize(fd); > - int flags; > - int map_sync_flags = 0; > - size_t offset; > - size_t total; > - void *guardptr; > - void *ptr; > + size_t offset, total; > + void *ptr, *guardptr; > > /* > * Note: this always allocates at least one extra page of virtual address > @@ -153,44 +193,9 @@ void *qemu_ram_mmap(int fd, > /* Always align to host page size */ > assert(align >= pagesize); > > - flags = MAP_FIXED; > - flags |= fd == -1 ? MAP_ANONYMOUS : 0; > - flags |= shared ? MAP_SHARED : MAP_PRIVATE; > - if (shared && is_pmem) { > - map_sync_flags = MAP_SYNC | MAP_SHARED_VALIDATE; > - } > - > offset = QEMU_ALIGN_UP((uintptr_t)guardptr, align) - (uintptr_t)guardptr; > > - ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE, > - flags | map_sync_flags, fd, 0); > - > - if (ptr == MAP_FAILED && map_sync_flags) { > - if (errno == ENOTSUP) { > - char *proc_link, *file_name; > - int len; > - proc_link = g_strdup_printf("/proc/self/fd/%d", fd); > - file_name = g_malloc0(PATH_MAX); > - len = readlink(proc_link, file_name, PATH_MAX - 1); > - if (len < 0) { > - len = 0; > - } > - file_name[len] = '\0'; > - fprintf(stderr, "Warning: requesting persistence across crashes " > - "for backend file %s failed. Proceeding without " > - "persistence, data might become corrupted in case of host " > - "crash.\n", file_name); > - g_free(proc_link); > - g_free(file_name); > - } > - /* > - * if map failed with MAP_SHARED_VALIDATE | MAP_SYNC, > - * we will remove these flags to handle compatibility. > - */ > - ptr = mmap(guardptr + offset, size, PROT_READ | PROT_WRITE, > - flags, fd, 0); > - } > - > + ptr = mmap_populate(guardptr + offset, size, fd, shared, is_pmem); > if (ptr == MAP_FAILED) { > munmap(guardptr, total); > return MAP_FAILED; > -- Murilo