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Fri, 16 Aug 2019 21:07:14 +0000 (UTC) Received: from apollo.usersys.redhat.com (unused-10-15-17-159.yyz.redhat.com [10.15.17.159]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C83175D9DC; Fri, 16 Aug 2019 21:07:10 +0000 (UTC) To: Eduardo Habkost , Markus Armbruster References: <20190815183803.13346-1-ehabkost@redhat.com> <20190815183803.13346-4-ehabkost@redhat.com> <87pnl5sks3.fsf@dusky.pond.sub.org> <20190816074932.GK13569@beluga.usersys.redhat.com> <87h86hpae5.fsf@dusky.pond.sub.org> <20190816174241.GE3908@habkost.net> From: Yash Mankad Openpgp: preference=signencrypt Autocrypt: addr=ymankad@redhat.com; prefer-encrypt=mutual; keydata= mQENBFecwEYBCAC7QUnuTKRrz39gLumVG+KNB8XmHqHKypYPMkdJNLx33LAhmDVEeBEB6Zyn ryVtNClL4GVrmDOROp53kIkJh4uSAeu71w3/RJLrrHIs/NlFZ1cH3hEAwShLKYkXoVfqBN3m zhbqyndmPy8fviOIDcyzEBEIDbgsLgMebJTAto/ihLgEeG9dMF4qUuCcb3sWIao/WHSr9XHB OtZnvVUGueIM3DqEC2g5BN8025riOOL3UGRmIctJR+2dM+j0aCIbARGv1B66o300gJfjxm24 /CbD/I6Wt2PHrNv/d4nXjfNElaBCiVw9513m2maFJeFaSPJpAGZjyDN/niNcpvxg6XaLABEB AAG0P1lhc2ggTWFua2FkIChTb2Z0d2FyZSBFbmdpbmVlciBhdCBSZWQgSGF0KSA8eW1hbmth ZEByZWRoYXQuY29tPokBNwQTAQgAIQUCV5zARgIbAwULCQgHAgYVCAkKCwIEFgIDAQIeAQIX gAAKCRBjP1s2LzTrMJhfB/9mRNS3eMAy17wRSjnR1/AtNZ2qwBbyjnor0+Q7UfYUXKvFBNJo LnX6zphFJ/fZMqIM5BrE7T90Mm5Qy3qoK1c0QibN97OECrPn9epGPKiiI+1WZrIX9S3crCui hyIS4IuOOmgtVJx+akWCbfYPaybNsTPLBFJZ0+aATSe9Nbeb4XUS3RAqlRUEdejNGxxtKLtZ xgXsmL/il6Fp4EX53H1+d83Rk4V+S2KvMfrFEB+mxF7JFUv0E071br42po/EDnYj2wLM/STh Fgp5LO4qTPrwD8mllibLSF6ZCrjNYW1EctJF7oYbfFXwPUh9LWh0opKwzo8ne5ZN/4hzexHU 4MnquQENBFecwEYBCACnrkQgxRis8b1DRRIWu+Gxxp4Xv85c19A3IyNudvihSNSSV8mSZ+ei 9Xev80IhgExf+1MeTPvuWmD1FogqC5Pi6bEs29ZZvSde+DH1BeVoKVn4zY+rCSqyrlRfx8Zd xJXIICfOgfDRjDf0nKPiI14ujdT0zMOPJHQ8wf267kMWmS32eQPTLJmemhl9WhEett+i1WLq 84DjbEhtkTO6FdboEcTN1fMSpkXz+jgfvgCCZIfJJ+AI/V/VjBBn264VdDdOE/AFfc6B1QYf 6X3npdUmXjlE5QIadoaOHf6e+qMSEchKfMa9ban0dH1THVAm2Z8Ji+l0tNYJ/e3mndXcVJv7 ABEBAAGJAR8EGAEIAAkFAlecwEYCGwwACgkQYz9bNi806zAlVwgAj0auI5iVWxdCEnxGDAFC 7uuZeBfiRGUwnaeRLcs2N6zLdN7Y9aoLv0RMrQhTP1DiIOi2xuCiUeGAY533fIpQOtE+AHgY fFqUG9gwK9Web5Tec+SNOBXeULRd8flo3RIkKMUR6RBynHkvEt2WbGRfr4gP6RuYzwBL1EWv nigkhVXsLA+hyut5C8OMXcxG61vbat2duyBgqROV0UbMau9Nr+t5w2isusgHe3fia1h5uwsh 3UDO4xAD/Il16hZqcPbgKW3+S7uR3V2LKwCqX0S/9gYwaIfiBgvEt7EAbj2YZfYvcWjbBwDu stjeTrSRCejEli4lN7PsSM6/NaLsIPKMgQ== Message-ID: <75655410-9af9-e463-9471-675299929bde@redhat.com> Date: Fri, 16 Aug 2019 17:07:10 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190816174241.GE3908@habkost.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Fri, 16 Aug 2019 21:07:14 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 3/3] pc: Don't make CPU properties mandatory unless necessary 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: Peter Krempa , Like Xu , Erik Skultety , "Michael S. Tsirkin" , qemu-devel@nongnu.org, Igor Mammedov , Paolo Bonzini , Miroslav Rezanina , "Danilo C. L. de Paula" , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 8/16/19 1:42 PM, Eduardo Habkost wrote: > On Fri, Aug 16, 2019 at 02:22:58PM +0200, Markus Armbruster wrote: >> Erik Skultety writes: >> >>> On Fri, Aug 16, 2019 at 08:10:20AM +0200, Markus Armbruster wrote: >>>> Eduardo Habkost writes: >>>> >>>>> We have this issue reported when using libvirt to hotplug CPUs: >>>>> https://bugzilla.redhat.com/show_bug.cgi?id=3D1741451 >>>>> >>>>> Basically, libvirt is not copying die-id from >>>>> query-hotpluggable-cpus, but die-id is now mandatory. >>>> Uh-oh, "is now mandatory": making an optional property mandatory is = an >>>> incompatible change. When did we do that? Commit hash, please. >>>> >>>> [...] >>>> >>> I don't even see it as being optional ever - the property wasn't even= >>> recognized before commit 176d2cda0de introduced it as mandatory. >> Compatibility break. >> >> Commit 176d2cda0de is in v4.1.0. If I had learned about it a bit >> earlier, I would've argued for a last minute fix or a revert. Now we >> have a regression in the release. >> >> Eduardo, I think this fix should go into v4.1.1. Please add cc: >> qemu-stable. > I did it in v2. > >> How can we best avoid such compatibility breaks to slip in undetected?= >> >> A static checker would be nice. For vmstate, we have >> scripts/vmstate-static-checker.py. Not sure it's used. > I don't think this specific bug would be detected with a static > checker. "die-id is mandatory" is not something that can be > extracted by looking at QOM data structures. The new rule was > being enforced by the hotplug handler callbacks, and the hotplug > handler call tree is a bit complex (too complex for my taste, but > I digress). > > We could have detected this with a simple CPU hotplug automated > test case, though. Or with a very simple -device test case like > the one I have submitted with this patch. > > This was detected by libvirt automated test cases. It would be > nice if this was run during the -rc stage and not only after the > 4.1.0 release, though. > > I don't know details of the test job. Danilo, Mirek, Yash: do > you know how this bug was detected, and what we could do to run > the same test jobs in upstream QEMU release candidates? This bug was caught by our internal gating tests. The libvirt gating tests for the virt module include the following Avocado-VT test case: libvirt_vcpu_plug_unplug.positive_test.vcpu_set.live.vm_operate.save This job failed with the error that you can see in the description of the BZ#1741451 [0]. If you think that this would have been caught by a simple hotplug case, I'd recommend adding a test for hotplug to avocado_qemu. Otherwise, if you want, I can look into adding this particular libvirt test case to our QEMU CI efforts. Thanks, Yash [0] https://bugzilla.redhat.com/show_bug.cgi?id=3D1741451#c0 >