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Mon, 16 Mar 2026 11:56:19 +0000 (GMT) Date: Mon, 16 Mar 2026 12:56:18 +0100 From: Heiko Carstens To: Christian Borntraeger Cc: KVM , Janosch Frank , David Hildenbrand , linux-s390 , Thomas Huth , Claudio Imbrenda , Vasily Gorbik , Alexander Gordeev Subject: Re: [PATCH/RFC] KVM: s390: vsie: Avoid injecting machine check on signal Message-ID: <20260316115618.17080B45-hca@linux.ibm.com> References: <20260316103934.13368-1-borntraeger@linux.ibm.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260316103934.13368-1-borntraeger@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzE2MDA4OSBTYWx0ZWRfX1M1Xw+wlKZww 1CniPRBXLds4GYmwAxyCLiegN1f7XiKiXFpSVMMAoMZ6z5IUELVlnu53no/GIida1cFkWf1vQxB Sl4NWc0MIu4vwJJTYwz3a03aiOiXR0ikghaKvA+4KCrQdzGLo0s8dVTSfN91DLc/jveKgaUu4oH SLiv43vgrDTJoN6kP+BR+MniuuO2ek4A21LvuVoeXX0fjaJyRblpDZT7GcvPArM8xjkUCTeScak qC7WSCICGOC34v06beDo1FTTnpb6n+OZABxdrT05v9qzzvqDKwEX9KZIOQ3Ax/pbwf3hTRSPruh NV5tb+W6VKXdih0iKx3obYASlVcW8m3hoKnTZGO1qff0fF+fwXLH6iz3Slpi9zYxvXgCirYSt4G hgPk99XDC5a8Oma9lS76OVJxV/c8wZh89CqE5Js/SWeD5xFuVif4XwZNHSOeZeYryM6WKPoBKwM ZKNv/H+lUOx0PPdZOKA== X-Authority-Analysis: v=2.4 cv=GIQF0+NK c=1 sm=1 tr=0 ts=69b7efe9 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=kj9zAlcOel0A:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=v_eQMfJJpqUdI5PqWLMA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: UxzKBkraGr6uDmCj981DFaQ8RI0g8PwR X-Proofpoint-GUID: UxzKBkraGr6uDmCj981DFaQ8RI0g8PwR X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-16_04,2026-03-16_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 priorityscore=1501 bulkscore=0 lowpriorityscore=0 malwarescore=0 phishscore=0 impostorscore=0 suspectscore=0 adultscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603160089 On Mon, Mar 16, 2026 at 11:39:34AM +0100, Christian Borntraeger wrote: > The recent XFER_TO_GUEST_WORK change resulted in a situation, where the > vsie code would interpret a signal during work as a machine check during > SIE as both use the EINTR return code. > > Fixes: 2bd1337a1295e ("KVM: s390: Use generic VIRT_XFER_TO_GUEST_WORK functions") > Signed-off-by: Christian Borntraeger > --- > arch/s390/kvm/vsie.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) ... > - if (rc == -EINTR) { > + if (!skipped && rc == -EINTR) { > kvm_s390_reinject_machine_check(vcpu, &vsie_page->mcck_info); > return 0; As far as I can tell __SF_SIE_REASON is only used for passing -EINTR in case of a machine check, otherwise it is unused (== zero)? So the KVM_EXIT* codes don't work instead of -EINTR, since those are uapi, and there is nothing that would match a machine check anyway. However I would still propose to pass some unique positive number back via the stackframe instead of some random negative error number which means nothing. That is: change the machine check handler to pass e.g. #define KVM_S390_SIE_EXIT_MCCK 1 *((long *)(regs->gprs[15] + __SF_SIE_REASON)) = KVM_S390_SIE_EXIT_MCCK; Which would make it much more obvious what happens, and which would also avoid such strange bugs. Just my 0.02.