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Wed, 26 Nov 2025 12:31:30 +0000 (GMT) Message-ID: <6a717d9b-3771-41f2-9964-442fb6f68fb2@linux.ibm.com> Date: Wed, 26 Nov 2025 13:31:30 +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 v2 2/3] KVM: s390: Enable and disable interrupts in entry code To: Andrew Donnellan , kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Christian Borntraeger , Claudio Imbrenda , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle Cc: Nicholas Miehlbradt , Thomas Gleixner , Peter Zijlstra , Andy Lutomirski , David Hildenbrand References: <20251126-s390-kvm-xfer-to-guest-work-v2-0-1b8767879235@linux.ibm.com> <20251126-s390-kvm-xfer-to-guest-work-v2-2-1b8767879235@linux.ibm.com> Content-Language: en-US From: Janosch Frank Autocrypt: addr=frankja@linux.ibm.com; keydata= xsFNBFubpD4BEADX0uhkRhkj2AVn7kI4IuPY3A8xKat0ihuPDXbynUC77mNox7yvK3X5QBO6 qLqYr+qrG3buymJJRD9xkp4mqgasHdB5WR9MhXWKH08EvtvAMkEJLnqxgbqf8td3pCQ2cEpv 15mH49iKSmlTcJ+PvJpGZcq/jE42u9/0YFHhozm8GfQdb9SOI/wBSsOqcXcLTUeAvbdqSBZe zuMRBivJQQI1esD9HuADmxdE7c4AeMlap9MvxvUtWk4ZJ/1Z3swMVCGzZb2Xg/9jZpLsyQzb lDbbTlEeyBACeED7DYLZI3d0SFKeJZ1SUyMmSOcr9zeSh4S4h4w8xgDDGmeDVygBQZa1HaoL Esb8Y4avOYIgYDhgkCh0nol7XQ5i/yKLtnNThubAcxNyryw1xSstnKlxPRoxtqTsxMAiSekk 0m3WJwvwd1s878HrQNK0orWd8BzzlSswzjNfQYLF466JOjHPWFOok9pzRs+ucrs6MUwDJj0S cITWU9Rxb04XyigY4XmZ8dywaxwi2ZVTEg+MD+sPmRrTw+5F+sU83cUstuymF3w1GmyofgsU Z+/ldjToHnq21MNa1wx0lCEipCCyE/8K9B9bg9pUwy5lfx7yORP3JuAUfCYb8DVSHWBPHKNj HTOLb2g2UT65AjZEQE95U2AY9iYm5usMqaWD39pAHfhC09/7NQARAQABzSVKYW5vc2NoIEZy YW5rIDxmcmFua2phQGxpbnV4LmlibS5jb20+wsF3BBMBCAAhBQJbm6Q+AhsjBQsJCAcCBhUI CQoLAgQWAgMBAh4BAheAAAoJEONU5rjiOLn4p9gQALjkdj5euJVI2nNT3/IAxAhQSmRhPEt0 AmnCYnuTcHRWPujNr5kqgtyER9+EMQ0ZkX44JU2q7OWxTdSNSAN/5Z7qmOR9JySvDOf4d3mS bMB5zxL9d8SbnSs1uW96H9ZBTlTQnmLfsiM9TetAjSrR8nUmjGhe2YUhJLR1v1LguME+YseT eXnLzIzqqpu311/eYiiIGcmaOjPCE+vFjcXL5oLnGUE73qSYiujwhfPCCUK0850o1fUAYq5p CNBCoKT4OddZR+0itKc/cT6NwEDwdokeg0+rAhxb4Rv5oFO70lziBplEjOxu3dqgIKbHbjza EXTb+mr7VI9O4tTdqrwJo2q9zLqqOfDBi7NDvZFLzaCewhbdEpDYVu6/WxprAY94hY3F4trT rQMHJKQENtF6ZTQc9fcT5I3gAmP+OEvDE5hcTALpWm6Z6SzxO7gEYCnF+qGXqp8sJVrweMub UscyLqHoqdZC2UG4LQ1OJ97nzDpIRe0g6oJ9ZIYHKmfw5jjwH6rASTld5MFWajWdNsqK15k/ RZnHAGICKVIBOBsq26m4EsBlfCdt3b/6emuBjUXR1pyjHMz2awWzCq6/6OWs5eANZ0sdosNq dq2v0ULYTazJz2rlCXV89qRa7ukkNwdBSZNEwsD4eEMicj1LSrqWDZMAALw50L4jxaMD7lPL jJbazsFNBFubpD4BEADAcUTRqXF/aY53OSH7IwIK9lFKxIm0IoFkOEh7LMfp7FGzaP7ANrZd cIzhZi38xyOkcaFY+npGEWvko7rlIAn0JpBO4x3hfhmhBD/WSY8LQIFQNNjEm3vzrMo7b9Jb JAqQxfbURY3Dql3GUzeWTG9uaJ00u+EEPlY8zcVShDltIl5PLih20e8xgTnNzx5c110lQSu0 iZv2lAE6DM+2bJQTsMSYiwKlwTuv9LI9Chnoo6+tsN55NqyMxYqJgElk3VzlTXSr3+rtSCwf tq2cinETbzxc1XuhIX6pu/aCGnNfuEkM34b7G1D6CPzDMqokNFbyoO6DQ1+fW6c5gctXg/lZ 602iEl4C4rgcr3+EpfoPUWzKeM8JXv5Kpq4YDxhvbitr8Dm8gr38+UKFZKlWLlwhQ56r/zAU v6LIsm11GmFs2/cmgD1bqBTNHHcTWwWtRTLgmnqJbVisMJuYJt4KNPqphTWsPY8SEtbufIlY HXOJ2lqUzOReTrie2u0qcSvGAbSfec9apTFl2Xko/ddqPcZMpKhBiXmY8tJzSPk3+G4tqur4 6TYAm5ouitJsgAR61Cu7s+PNuq/pTLDhK+6/Njmc94NGBcRA4qTuysEGE79vYWP2oIAU4Fv6 gqaWHZ4MEI2XTqH8wiwzPdCQPYsSE0fXWiYu7ObeErT6iLSTZGx4rQARAQABwsFfBBgBCAAJ BQJbm6Q+AhsMAAoJEONU5rjiOLn4DDEP/RuyckW65SZcPG4cMfNgWxZF8rVjeVl/9PBfy01K 8R0hajU40bWtXSMiby7j0/dMjz99jN6L+AJHJvrLz4qYRzn2Ys843W+RfXj62Zde4YNBE5SL jJweRCbMWKaJLj6499fctxTyeb9+AMLQS4yRSwHuAZLmAb5AyCW1gBcTWZb8ON5BmWnRqeGm IgC1EvCnHy++aBnHTn0m+zV89BhTLTUal35tcjUFwluBY39R2ux/HNlBO1GY3Z+WYXhBvq7q katThLjaQSmnOrMhzqYmdShP1leFTVbzXUUIYv/GbynO/YrL2gaQpaP1bEUEi8lUAfXJbEWG dnHFkciryi092E8/9j89DJg4mmZqOau7TtUxjRMlBcIliXkzSLUk+QvD4LK1kWievJse4mte FBdkWHfP4BH/+8DxapRcG1UAheSnSRQ5LiO50annOB7oXF+vgKIaie2TBfZxQNGAs3RQ+bga DchCqFm5adiSP5+OT4NjkKUeGpBe/aRyQSle/RropTgCi85pje/juYEn2P9UAgkfBJrOHvQ9 Z+2Sva8FRd61NJLkCJ4LFumRn9wQlX2icFbi8UDV3do0hXJRRYTWCxrHscMhkrFWLhYiPF4i phX7UNdOWBQ90qpHyAxHmDazdo27gEjfvsgYMdveKknEOTEb5phwxWgg7BcIDoJf9UMC In-Reply-To: <20251126-s390-kvm-xfer-to-guest-work-v2-2-1b8767879235@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTIyMDAyMSBTYWx0ZWRfX6qZGY5Tc65O6 lKKoMc+fLrGUPx7g969+lRiB8hWb0xGwVUbMHLWN8Dhzwnv5+GEJIWVpRwKyRULjunKsFc8kNKY wKB/0L0Mio/HzDCS5uS9F6FjqFec9zzGRwti3mZuZGPAARIXSiG830eZo8qGJMTLKRXM1V9vy8Z XPplbQEtmA/z3cWca+HwTQLkakJz96kvRz8Q9ZzTMU1CNj1oH8LvAQze+vTcrAAaHcWupyfwvIV ZxYObCbslgsa/ACnzfy1iuyFMTqmtMwTG9xXxXXWGCYvpkImdVBxyrfdDSbhik3Ol8VeQblccLe syGXZl9sRE7Trl5cr9uFfZMJF/O7J9/WHbBNHaa0W99cDju96LakRn2i767FP25ry3JHa9nIdqA zN4Uc+clYmH1/Wdp2tkTI0x7q8vZhA== X-Proofpoint-ORIG-GUID: 46FxQu0SCT_BAl1SthDUfVaTmYPp2ZXg X-Proofpoint-GUID: 46FxQu0SCT_BAl1SthDUfVaTmYPp2ZXg X-Authority-Analysis: v=2.4 cv=TMJIilla c=1 sm=1 tr=0 ts=6926f32d cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=5oxjjmwJqIIfr6gTb_cA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-25_02,2025-11-25_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 spamscore=0 phishscore=0 impostorscore=0 clxscore=1015 adultscore=0 bulkscore=0 suspectscore=0 malwarescore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511220021 On 11/26/25 06:33, Andrew Donnellan wrote: > From: Heiko Carstens > > Move enabling and disabling of interrupts around the SIE instruction to > entry code. Enabling interrupts only after the __TI_sie flag has been set > guarantees that the SIE instruction is not executed if an interrupt happens > between enabling interrupts and the execution of the SIE instruction. > Interrupt handlers and machine check handler forward the PSW to the > sie_exit label in such cases. > > This is a prerequisite for VIRT_XFER_TO_GUEST_WORK to prevent that guest > context is entered when e.g. a scheduler IPI, indicating that a reschedule > is required, happens right before the SIE instruction, which could lead to > long delays. > > Signed-off-by: Heiko Carstens > Tested-by: Andrew Donnellan > Signed-off-by: Andrew Donnellan Reviewed-by: Janosch Frank > --- > arch/s390/include/asm/stacktrace.h | 1 + > arch/s390/kernel/asm-offsets.c | 1 + > arch/s390/kernel/entry.S | 2 ++ > arch/s390/kvm/kvm-s390.c | 5 ----- > 4 files changed, 4 insertions(+), 5 deletions(-) > > diff --git a/arch/s390/include/asm/stacktrace.h b/arch/s390/include/asm/stacktrace.h > index 810a6b9d96280f73311de873ad180c59a0cfbd5f..c9ae680a28af910c4703eee179be4db6c1ec9ad1 100644 > --- a/arch/s390/include/asm/stacktrace.h > +++ b/arch/s390/include/asm/stacktrace.h > @@ -66,6 +66,7 @@ struct stack_frame { > unsigned long sie_flags; > unsigned long sie_control_block_phys; > unsigned long sie_guest_asce; > + unsigned long sie_irq; > }; > }; > unsigned long gprs[10]; > diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c > index a8915663e917faed4551276b64013ee073662cc9..730449f464aff25761264b00d63d92e907f17f78 100644 > --- a/arch/s390/kernel/asm-offsets.c > +++ b/arch/s390/kernel/asm-offsets.c > @@ -64,6 +64,7 @@ int main(void) > OFFSET(__SF_SIE_FLAGS, stack_frame, sie_flags); > OFFSET(__SF_SIE_CONTROL_PHYS, stack_frame, sie_control_block_phys); > OFFSET(__SF_SIE_GUEST_ASCE, stack_frame, sie_guest_asce); > + OFFSET(__SF_SIE_IRQ, stack_frame, sie_irq); > DEFINE(STACK_FRAME_OVERHEAD, sizeof(struct stack_frame)); > BLANK(); > OFFSET(__SFUSER_BACKCHAIN, stack_frame_user, back_chain); > diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S > index 75b0fbb236d05f420b20cac6bac925e8ac36fa68..e906f4ab6cf35e53061a27192911629c10c347ed 100644 > --- a/arch/s390/kernel/entry.S > +++ b/arch/s390/kernel/entry.S > @@ -189,6 +189,7 @@ SYM_FUNC_START(__sie64a) > mvc __SF_SIE_FLAGS(8,%r15),__TI_flags(%r14) # copy thread flags > lmg %r0,%r13,0(%r4) # load guest gprs 0-13 > mvi __TI_sie(%r14),1 > + stosm __SF_SIE_IRQ(%r15),0x03 # enable interrupts > lctlg %c1,%c1,__SF_SIE_GUEST_ASCE(%r15) # load primary asce > lg %r14,__SF_SIE_CONTROL(%r15) # get control block pointer > oi __SIE_PROG0C+3(%r14),1 # we are going into SIE now > @@ -212,6 +213,7 @@ SYM_FUNC_START(__sie64a) > lg %r14,__LC_CURRENT(%r14) > mvi __TI_sie(%r14),0 > SYM_INNER_LABEL(sie_exit, SYM_L_GLOBAL) > + stnsm __SF_SIE_IRQ(%r15),0xfc # disable interrupts > lg %r14,__SF_SIE_SAVEAREA(%r15) # load guest register save area > stmg %r0,%r13,0(%r14) # save guest gprs 0-13 > xgr %r0,%r0 # clear guest registers to > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index fa6b5150ca31e4d9f0bdafabc1fb1d90ef3f3d0d..3cad08662b3d80aaf6f5f8891fc08b383c3c44d4 100644 > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c > @@ -5075,13 +5075,8 @@ int noinstr kvm_s390_enter_exit_sie(struct kvm_s390_sie_block *scb, > * The guest_state_{enter,exit}_irqoff() functions inform lockdep and > * tracing that entry to the guest will enable host IRQs, and exit from > * the guest will disable host IRQs. > - * > - * We must not use lockdep/tracing/RCU in this critical section, so we > - * use the low-level arch_local_irq_*() helpers to enable/disable IRQs. > */ > - arch_local_irq_enable(); > ret = sie64a(scb, gprs, gasce); > - arch_local_irq_disable(); > > guest_state_exit_irqoff(); > >