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Mon, 16 Mar 2026 12:00:46 +0000 (GMT) Message-ID: Date: Mon, 16 Mar 2026 13:00:46 +0100 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH/RFC] KVM: s390: vsie: Avoid injecting machine check on signal To: Heiko Carstens Cc: KVM , Janosch Frank , David Hildenbrand , linux-s390 , Thomas Huth , Claudio Imbrenda , Vasily Gorbik , Alexander Gordeev References: <20260316103934.13368-1-borntraeger@linux.ibm.com> <20260316115618.17080B45-hca@linux.ibm.com> Content-Language: en-US From: Christian Borntraeger In-Reply-To: <20260316115618.17080B45-hca@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: pxvx8xYm--ZvdmtcaL1GTnPKroK5iFrx X-Proofpoint-GUID: pxvx8xYm--ZvdmtcaL1GTnPKroK5iFrx X-Authority-Analysis: v=2.4 cv=KYnfcAYD c=1 sm=1 tr=0 ts=69b7f0f3 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=EfE3EK5EhESzuKWg8UQA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzE2MDA4OSBTYWx0ZWRfX1Aj7FhWAEjFZ xSpRQO83ax6orvctNq6+NxKHyeOHsRMxw/crz0DgGiofAVg2z/+rfOlJTOUxoM3OpbiY6cj4OMx J4PVG19IiKBs/CkCa5uKI/SyvT593CSrgOmbJVc4laJdP6zQGIgkHtJk9GrPRMFr4O/KaxV2iVL oL+zP/3D95f7qBJKjHZeyYDWy456v1Nwg0IIj7c7CNbub9JmG2TW0R/ncAXv9Lwr8NmfOIzOtY9 kcvxDYf2d/mbdAOLnCPiURpOo/iymeYIWGSBZGBCFSS1DyY2fp6BnvuN7iRWeq188GXGKLZFKzE flHdiWQs3pxsiy42guXMpt586FYhgd0AGZUh7RqHzF4ziQJWmLyJKMJbFjMFOFBn+dsQ4g08bJ4 nkWnUZXt0vU++844M/kWTe0uoY66nD26Htlu12TyiLJRDeEF+YHJCUPzDQdZ3VkLPjJQJz5HY5e MNkOAce8RsGpIWVyJUg== 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 phishscore=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 bulkscore=0 spamscore=0 impostorscore=0 malwarescore=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 Am 16.03.26 um 12:56 schrieb Heiko Carstens: > 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. Yes, this was just a minimal "try to fix and get feedback" and thus an RFC. Will have a look on your proposal.