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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 24 Jan 2020 13:00:34 -0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 00OD0YYV62914618 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 24 Jan 2020 13:00:34 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F1C5AAE05F; Fri, 24 Jan 2020 13:00:33 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A7C5EAE059; Fri, 24 Jan 2020 13:00:33 +0000 (GMT) Received: from localhost.localdomain (unknown [9.145.180.45]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 24 Jan 2020 13:00:33 +0000 (GMT) Subject: Re: [PATCH] s390x: sigp: Fix sense running reporting To: David Hildenbrand , Cornelia Huck References: <20200124100137.28656-1-frankja@linux.ibm.com> <20200124110547.50c73851.cohuck@redhat.com> <63618540-bc70-918a-6a26-14656f66742f@redhat.com> From: Janosch Frank Autocrypt: addr=frankja@linux.ibm.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <63618540-bc70-918a-6a26-14656f66742f@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="4SjR6a11OpgNIW6PpgKvnA0rIiPjbzP64" X-TM-AS-GCONF: 00 x-cbid: 20012413-4275-0000-0000-0000039A8998 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20012413-4276-0000-0000-000038AE9A02 Message-Id: <88a233f5-31d0-fef9-b80a-8d31a8fb7d65@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.572 definitions=2020-01-24_03:2020-01-24, 2020-01-24 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 impostorscore=0 clxscore=1015 adultscore=0 mlxlogscore=999 priorityscore=1501 spamscore=0 bulkscore=0 lowpriorityscore=0 malwarescore=0 mlxscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-2001240107 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] X-Received-From: 148.163.156.1 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: borntraeger@de.ibm.com, qemu-s390x@nongnu.org, thuth@redhat.com, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --4SjR6a11OpgNIW6PpgKvnA0rIiPjbzP64 Content-Type: multipart/mixed; boundary="Ey2lfihp3w0AsRm3ybBkcPPIIFUaGD9Fk" --Ey2lfihp3w0AsRm3ybBkcPPIIFUaGD9Fk Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 1/24/20 1:03 PM, David Hildenbrand wrote: > On 24.01.20 11:05, Cornelia Huck wrote: >> On Fri, 24 Jan 2020 05:01:37 -0500 >> Janosch Frank wrote: >> >>> The logic was inversed and reported running if the cpu was stopped. >> >> s/inversed/inverted/ ? >> >>> Let's fix that. >>> >> >> Fixes: d1b468bc8869 ("s390x/tcg: implement SIGP SENSE RUNNING STATUS")= >> >>> Signed-off-by: Janosch Frank >>> --- >>> target/s390x/sigp.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/target/s390x/sigp.c b/target/s390x/sigp.c >>> index 727875bb4a..286c0d6c9c 100644 >>> --- a/target/s390x/sigp.c >>> +++ b/target/s390x/sigp.c >>> @@ -347,7 +347,7 @@ static void sigp_sense_running(S390CPU *dst_cpu, = SigpInfo *si) >>> } >>> =20 >>> /* If halted (which includes also STOPPED), it is not running */= >>> - if (CPU(dst_cpu)->halted) { >>> + if (!CPU(dst_cpu)->halted) { >>> si->cc =3D SIGP_CC_ORDER_CODE_ACCEPTED; >>> } else { >>> set_sigp_status(si, SIGP_STAT_NOT_RUNNING); >> >> I'm wondering why nobody noticed this before... >=20 > AFAIR, it "SENSE RUNNING" allows you to test if the target CPU is > scheduled by the hypervisor. So it is used for performance optimization= , > but correctness of a program barely depends on it. >=20 > a) You can always return "not running" and it would be totally fine >=20 > b) Return "running" would also most probably always valid (although it > does not make too much sense for STOPPED CPUs). >=20 > E.g., in KVM we set CPUSTAT_RUNNING whenever we load the CPU. This can > also happen (AFAIR) when the CPU state is already stopped (e.g., > currently getting stopped) or still sleeping (e.g., about to wake up, o= r > in kvm_vcpu_block()). >=20 >=20 > Long story short: There is no trusting on these values. That answer makes me highly uncomfortable... >=20 >=20 > But yeah, the heuristic we are using is sub-optimal. :) >=20 > Reviewed-by: David Hildenbrand Thanks! --Ey2lfihp3w0AsRm3ybBkcPPIIFUaGD9Fk-- --4SjR6a11OpgNIW6PpgKvnA0rIiPjbzP64 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEwGNS88vfc9+v45Yq41TmuOI4ufgFAl4q6nEACgkQ41TmuOI4 ufimXRAArZcAA2P6X7QUjj6tK8pURhlB8cKKR05VY+YR5p0z1nB6mjjTAcQvU3gy TKhbGQeOibXqq9cfMrpeY65pcX1AN8+EUM64Ta4IQ0UZxvCkHfuFYhgTixle9Je5 3SezGcPzBTyhJe25VtmpihILNIrqFz5itZTWvJlC4virsw9m69cb6qM1wFIF2zIJ 3cuR3fTPOj0bDuoJ/UHHyTHFHBsUtWDnQbtvSvpvKXzg7PKJ4W8aW0MoZMPqNtYN 5E+t2X3QesHqMuT1sKQVk2LOqY9OqlcMotff7LnuY1S10sZ1idg/ZLPRBGOd2843 iODnaVyDwYlG0ssYf+kPAjNTvoDJUWmyLSsPP7G9rROEuOJM/vendZZimB+uwAjj bh0wZgOgDU6kixhn0IFQCzz3H6ATiPOP7Nq1DySOzksgiksdkeqZgOjuMHS7siIr kHLXFOO3hMabhYln7RTJ36PHRoISsL42g803xHTlP8jPn3Z4lNs1Cq4Qlvk/qwDr 5QfunR9TvV5sP3PyAIU4aTKrypE/pV8PmZ3LoEcwPHaXKSPPQgQQGBK+p1Yk2c3p REL5uw6W2/vUanTlbutUwYd36Zqu8N9FYd5yoI4STyMARW0s57M+Dien66N1v+G7 aQt1ng5je50MyLnnHo9ZtrwVe40//QwWNwFz6M6rJiiN4b553XM= =roos -----END PGP SIGNATURE----- --4SjR6a11OpgNIW6PpgKvnA0rIiPjbzP64--