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Wed, 23 Sep 2026 14:04:11 +0000 (GMT) Received: from [9.111.80.133] (unknown [9.111.80.133]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 23 Sep 2026 14:04:11 +0000 (GMT) Message-ID: <45f3d2f6-75af-41eb-b8b5-a7cf42f345fa@linux.ibm.com> Date: Wed, 23 Sep 2026 16:04:11 +0200 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 12/21] KVM: s390: vsie: Add helper unshadow_intercept() To: Christoph Schlameuss , kvm@vger.kernel.org, linux-s390@vger.kernel.org Cc: Alexander Gordeev , Christian Borntraeger , Claudio Imbrenda , David Hildenbrand , Eric Farman , Heiko Carstens , Nico Boehr , Sven Schnelle , Vasily Gorbik , Paolo Bonzini , Shuah Khan , Sean Christopherson References: <20260918-vsie-sigpi-v7-0-f39806eaae37@linux.ibm.com> <20260918-vsie-sigpi-v7-12-f39806eaae37@linux.ibm.com> Content-Language: en-US From: Janosch Frank Autocrypt: addr=frankja@linux.ibm.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: 2cgAq6lgY9znredeS3RAqFXJpThcKX-L X-Authority-Analysis: v=2.4 cv=EOCTQFZC c=1 sm=1 tr=0 ts=6ab3dc60 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=RxkZ1HasL-odzlW5mFoA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Info: AW1haW4tMjYwOTIzMDA1NCBTYWx0ZWRfX5nMwD1lRw+dU 4bWn1PTuusDgrLHzDHK3JLGf0IJkXfAq3axOeXZdwRuPCxDz7Adc9YSfM4tcLDo4XQy3/cuCqen i0YCHEbBjr/j6PpdukpuglmBrEzml+I= X-Proofpoint-GUID: 7dA67ctnDgLmXqpYMYGS881bufEIzd5_ X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTIzMDA1NCBTYWx0ZWRfX1Bt5RAFzmEb2 ZR9Fvp4FB+SRcV2iiErVdu7SFExaYUyBjp9dcXXnpnU4B3DWV8FepBP6AYrIWqNjeHozCgApSvE cKwHpEoq+vGmwgCq6NBhGxD6Madv/9FdGb2Ce7phiQiFGAYh6OyaOwGrhokYsrIZfEBbz+0L6ul tFYgTc6Q+nFrY9svuFSXoyUcFNp+34wuTc71TNQmcVo1kFEWylmmoYKE3bZitHza27gjav+iHAC emiKpSq3/yN458HfWWOEReZ7ZrSGwjnOlaj9jXwzFvC7whBvaA/F5t9KUf4GNqqoupRdTvab7DS 4hAf/beaHv/b6PPKf+n0Oe/a4nT+mpwhUcFACVqw8mJSwbM6qoX/HnLhinC91SwAYK/SZfWiNMs I1t+BkfQCmH5MvdY03ISDD2ZBNMet1xQ595N72xK+YG0BpPcxqJYXAYKVcsqZouErAzjurEbl66 oQLCH7AF9Xrn1TgGoVA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-23_04,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 phishscore=0 priorityscore=1501 clxscore=1015 spamscore=0 adultscore=0 impostorscore=0 lowpriorityscore=0 suspectscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609230054 On 9/18/26 5:09 PM, Christoph Schlameuss wrote: > Extract helper method from existing code to reuse in new code. > > unshadow_intercept() acts like unshadow_scb() but only copies intercept > information. Used where the rest of the scb is not yet shadowed. > > Signed-off-by: Christoph Schlameuss > --- > arch/s390/kvm/s390/vsie.c | 28 ++++++++++++++++++++-------- > 1 file changed, 20 insertions(+), 8 deletions(-) > > diff --git a/arch/s390/kvm/s390/vsie.c b/arch/s390/kvm/s390/vsie.c > index 95baac9a1ccb..c42e2df4c0ab 100644 > --- a/arch/s390/kvm/s390/vsie.c > +++ b/arch/s390/kvm/s390/vsie.c > @@ -565,18 +565,27 @@ static void prepare_ibc(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page) > } > } > > -/* unshadow the scb, copying parameters back to the real scb */ > -static void unshadow_scb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page) > +/* > + * Only write the interception fields back; avoid clobbering the timer and > + * guest-state fields in scb_o. > + */ > +static inline void unshadow_intercept(struct kvm_s390_sie_block *scb_o, > + struct kvm_s390_sie_block *scb_s) > { > - struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s; > - struct kvm_s390_sie_block *scb_o = vsie_page->scb_o; > - > - /* interception */ > scb_o->icptcode = scb_s->icptcode; > scb_o->icptstatus = scb_s->icptstatus; > scb_o->ipa = scb_s->ipa; > scb_o->ipb = scb_s->ipb; > scb_o->gbea = scb_s->gbea; I have the feeling that we make things difficult for ourselves by not writing SIE entry validities into the scb_o directly. And I think you somewhat recognized that problem since you chose to write the validity to scb_o and not scb_s in _shadow_sca_cpu() but I have yet to fully read that patch. For 99% of the validities we've never even entered SIE so we copy data twice for absolutely no reason other than symmetry. out_unshadow in kvm_s390_handle_vsie() isn't really necessary, if pin_blocks() fails we can jump to unpin_scb() if we write the validity to scb_o. Maybe we could move (un)shadow_scb() into vsie_run() and be done with it. I have some more reading to do.