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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 31 Jul 2019 13:28:19 +0100 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x6VCSIZr43450730 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 31 Jul 2019 12:28:18 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 79B724C046; Wed, 31 Jul 2019 12:28:18 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1C9E04C044; Wed, 31 Jul 2019 12:28:18 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.152.224.71]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 31 Jul 2019 12:28:18 +0000 (GMT) To: Andrey Shinkevich , Paolo Bonzini , "qemu-devel@nongnu.org" , "qemu-block@nongnu.org" References: <1564502498-805893-1-git-send-email-andrey.shinkevich@virtuozzo.com> <1564502498-805893-4-git-send-email-andrey.shinkevich@virtuozzo.com> <14b60c5b-6ed4-0f4d-17a8-6ec861115c1e@redhat.com> <30f40221-d2d2-780b-3375-910e9f755edd@de.ibm.com> <08958a7e-1952-caf7-ab45-2fd503db418c@virtuozzo.com> From: Christian Borntraeger Openpgp: preference=signencrypt Autocrypt: addr=borntraeger@de.ibm.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <08958a7e-1952-caf7-ab45-2fd503db418c@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19073112-0016-0000-0000-00000297F2F5 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19073112-0017-0000-0000-000032F60621 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-07-31_05:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1907310126 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] X-Received-From: 148.163.158.5 Subject: Re: [Qemu-devel] [PATCH 3/3] i386/kvm: initialize struct at full before ioctl call 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: Vladimir Sementsov-Ogievskiy , "berto@igalia.com" , "ehabkost@redhat.com" , "kvm@vger.kernel.org" , Denis Lunev , "mtosatti@redhat.com" , "mdroth@linux.vnet.ibm.com" , "armbru@redhat.com" , "rth@twiddle.net" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 31.07.19 14:04, Andrey Shinkevich wrote: > On 31/07/2019 10:24, Christian Borntraeger wrote: >> >> >> On 30.07.19 21:20, Paolo Bonzini wrote: >>> On 30/07/19 18:01, Andrey Shinkevich wrote: >>>> Not the whole structure is initialized before passing it to the KVM. >>>> Reduce the number of Valgrind reports. >>>> >>>> Signed-off-by: Andrey Shinkevich >>> >>> Christian, is this the right fix? It's not expensive so it wouldn't be >>> an issue, just checking if there's any better alternative. >> >> I think all of these variants are valid with pros and cons >> 1. teach valgrind about this: >> Add to coregrind/m_syswrap/syswrap-linux.c (and the relevant header files) >> knowledge about which parts are actually touched. >> 2. use designated initializers >> 3. use memset >> 3. use a valgrind callback VG_USERREQ__MAKE_MEM_DEFINED to tell that this memory is defined >> > > Thank you all very much for taking part in the discussion. > Also, one may use the Valgrind technology to suppress the unwanted > reports by adding the Valgrind specific format file valgrind.supp to the > QEMU project. The file content is extendable for future needs. > All the cases we like to suppress will be recounted in that file. > A case looks like the stack fragments. For instance, from QEMU block: > > { > hw/block/hd-geometry.c > Memcheck:Cond > fun:guess_disk_lchs > fun:hd_geometry_guess > fun:blkconf_geometry > ... > fun:device_set_realized > fun:property_set_bool > fun:object_property_set > fun:object_property_set_qobject > fun:object_property_set_bool > } > > The number of suppressed cases are reported by the Valgrind with every > run: "ERROR SUMMARY: 5 errors from 3 contexts (suppressed: 0 from 0)" > > Andrey Yes, indeed that would be another variant. How performance critical are the fixed locations? That might have an impact on what is the best solution. >From a cleanliness approach doing 1 (adding the ioctl definition to valgrind) is certainly the most beautiful way. I did that in the past, look for example at https://sourceware.org/git/?p=valgrind.git;a=commitdiff;h=c2baee9b7bf043702c130de0771a4df439fcf403 or https://sourceware.org/git/?p=valgrind.git;a=commitdiff;h=00a31dd3d1e7101b331c2c83fca6c666ba35d910 for examples. > >>> >>> Paolo >>> >>>> --- >>>> target/i386/kvm.c | 3 +++ >>>> 1 file changed, 3 insertions(+) >>>> >>>> diff --git a/target/i386/kvm.c b/target/i386/kvm.c >>>> index dbbb137..ed57e31 100644 >>>> --- a/target/i386/kvm.c >>>> +++ b/target/i386/kvm.c >>>> @@ -190,6 +190,7 @@ static int kvm_get_tsc(CPUState *cs) >>>> return 0; >>>> } >>>> >>>> + memset(&msr_data, 0, sizeof(msr_data)); >>>> msr_data.info.nmsrs = 1; >>>> msr_data.entries[0].index = MSR_IA32_TSC; >>>> env->tsc_valid = !runstate_is_running(); >>>> @@ -1706,6 +1707,7 @@ int kvm_arch_init_vcpu(CPUState *cs) >>>> >>>> if (has_xsave) { >>>> env->xsave_buf = qemu_memalign(4096, sizeof(struct kvm_xsave)); >>>> + memset(env->xsave_buf, 0, sizeof(struct kvm_xsave)); >>>> } >>>> >>>> max_nested_state_len = kvm_max_nested_state_length(); >>>> @@ -3477,6 +3479,7 @@ static int kvm_put_debugregs(X86CPU *cpu) >>>> return 0; >>>> } >>>> >>>> + memset(&dbgregs, 0, sizeof(dbgregs)); >>>> for (i = 0; i < 4; i++) { >>>> dbgregs.db[i] = env->dr[i]; >>>> } >>>> -- >>>> 1.8.3.1 >>>> >>> >>> >> >