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Tue, 7 Apr 2020 10:59:14 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3020.oracle.com with ESMTP id 30741dv9tv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 07 Apr 2020 10:59:14 +0000 Received: from abhmp0009.oracle.com (abhmp0009.oracle.com [141.146.116.15]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 037AxDVc001565; Tue, 7 Apr 2020 10:59:13 GMT Received: from [10.175.215.143] (/10.175.215.143) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 07 Apr 2020 03:59:13 -0700 Subject: Re: [PATCH] exec: fetch the alignment of Linux devdax pmem character device nodes To: Jingqi Liu References: <20200401031314.11592-1-jingqi.liu@intel.com> From: Joao Martins Message-ID: Date: Tue, 7 Apr 2020 11:59:10 +0100 MIME-Version: 1.0 In-Reply-To: <20200401031314.11592-1-jingqi.liu@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9583 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=1 phishscore=0 malwarescore=0 bulkscore=0 spamscore=0 adultscore=0 mlxlogscore=999 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004070094 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9583 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 suspectscore=1 mlxlogscore=999 mlxscore=0 bulkscore=0 adultscore=0 priorityscore=1501 lowpriorityscore=0 clxscore=1011 malwarescore=0 impostorscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004070094 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 156.151.31.85 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: , Cc: Paolo Bonzini , Dan Williams , qemu-devel@nongnu.org, Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 4/1/20 4:13 AM, Jingqi Liu wrote: > If the backend file is devdax pmem character device, the alignment > specified by the option 'align=NUM' in the '-object memory-backend-file' > needs to match the alignment requirement of the devdax pmem character device. > > This patch fetches the devdax pmem file 'align', so that we can compare > it with the NUM of 'align=NUM'. > The NUM needs to be larger than or equal to the devdax pmem file 'align'. > > It also fixes the problem that mmap() returns failure in qemu_ram_mmap() > when the NUM of 'align=NUM' is less than the devdax pmem file 'align'. > > Cc: Dan Williams > Signed-off-by: Jingqi Liu > --- > exec.c | 46 +++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 45 insertions(+), 1 deletion(-) > > diff --git a/exec.c b/exec.c > index de9d949902..8221abffec 100644 > --- a/exec.c > +++ b/exec.c > @@ -1736,6 +1736,42 @@ static int64_t get_file_size(int fd) > return size; > } > > +static int64_t get_file_align(int fd) > +{ > + int64_t align = -1; > +#if defined(__linux__) > + struct stat st; > + > + if (fstat(fd, &st) < 0) { > + return -errno; > + } > + > + /* Special handling for devdax character devices */ > + if (S_ISCHR(st.st_mode)) { > + g_autofree char *subsystem_path = NULL; > + g_autofree char *subsystem = NULL; > + > + subsystem_path = g_strdup_printf("/sys/dev/char/%d:%d/subsystem", > + major(st.st_rdev), minor(st.st_rdev)); > + subsystem = g_file_read_link(subsystem_path, NULL); > + > + if (subsystem && g_str_has_suffix(subsystem, "/dax")) { > + g_autofree char *align_path = NULL; > + g_autofree char *align_str = NULL; > + > + align_path = g_strdup_printf("/sys/dev/char/%d:%d/device/align", > + major(st.st_rdev), minor(st.st_rdev)); > + Perhaps, you meant instead: /sys/dev/char/%d:%d/align ?