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Tue, 18 Nov 2025 15:10:06 +0000 (GMT) Date: Tue, 18 Nov 2025 16:10:05 +0100 From: Heiko Carstens To: Claudio Imbrenda Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, nsg@linux.ibm.com, nrb@linux.ibm.com, seiden@linux.ibm.com, schlameuss@linux.ibm.com, svens@linux.ibm.com, agordeev@linux.ibm.com, gor@linux.ibm.com, david@redhat.com, gerald.schaefer@linux.ibm.com Subject: Re: [PATCH v3 15/23] KVM: s390: Add helper functions for fault handling Message-ID: <20251118151005.9674Af1-hca@linux.ibm.com> References: <20251106161117.350395-1-imbrenda@linux.ibm.com> <20251106161117.350395-16-imbrenda@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: <20251106161117.350395-16-imbrenda@linux.ibm.com> X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=C/nkCAP+ c=1 sm=1 tr=0 ts=691c8c53 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=kj9zAlcOel0A:10 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=LOPTmjPZaZTW9MxM_NgA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-GUID: Yo6vZMqycVNGyNQgPrl6gW2JfRUnoGw2 X-Proofpoint-ORIG-GUID: Yo6vZMqycVNGyNQgPrl6gW2JfRUnoGw2 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTE1MDAzMiBTYWx0ZWRfX8pmXOInEZomW Zur1nUH9imTJ1lTT+H7WyUY7e/ZmRFBPbCwtkq5vgBwVdIXHUZDHy7Re2884WoRpMkhB9wwzedd ePeZvnQBoZ7/SdD7g4ovz200UgdqZpN7f0Wj7rI4lLsXVLwwWuS/tyXJtDZ9c/9VgGmsnHxMb8U GbwGFYvA0VQuRNR5Tr/XDjXZH7GccdR+mDnEiDpgSp787buxyzRJBbqynyUZNkoLlkBas4xz8NO pVRhdTAakMq5XOJXu7hpGOxi98SwpYQVtGPL5z25Rw59pV8S8NpKXgB1yyxoXT+FvtsIM/BOXQO vcOMq+gFCvgT7OMJoglwthFNe3hFCwltoXeRz//fFgi6d8sAeNizSGSrsthLUqAs9ULP/3kSN2H Y9BdIIXqB4shIMaJNb5tAhoc2dJXhw== 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=2025-11-18_01,2025-11-18_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 spamscore=0 impostorscore=0 bulkscore=0 malwarescore=0 suspectscore=0 clxscore=1015 lowpriorityscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511150032 On Thu, Nov 06, 2025 at 05:11:09PM +0100, Claudio Imbrenda wrote: > Add some helper functions for handling multiple guest faults at the > same time. > > This will be needed for VSIE, where a nested guest access also needs to > access all the page tables that map it. > > Signed-off-by: Claudio Imbrenda > --- > arch/s390/include/asm/kvm_host.h | 1 + > arch/s390/kvm/Makefile | 2 +- > arch/s390/kvm/faultin.c | 148 +++++++++++++++++++++++++++++++ > arch/s390/kvm/faultin.h | 92 +++++++++++++++++++ > arch/s390/kvm/kvm-s390.c | 2 +- > arch/s390/kvm/kvm-s390.h | 2 + > 6 files changed, 245 insertions(+), 2 deletions(-) > create mode 100644 arch/s390/kvm/faultin.c > create mode 100644 arch/s390/kvm/faultin.h ... > +int kvm_s390_faultin_gfn(struct kvm_vcpu *vcpu, struct kvm *kvm, struct guest_fault *f) > +{ ... > + scoped_guard(read_lock, &kvm->mmu_lock) { > + if (!mmu_invalidate_retry_gfn(kvm, inv_seq, f->gfn)) { > + f->valid = true; > + rc = gmap_link(mc, kvm->arch.gmap, f); > + kvm_release_faultin_page(kvm, f->page, !!rc, f->write_attempt); > + f->page = NULL; > + } > + } > + kvm_release_faultin_page(kvm, f->page, true, false); > + > + if (rc == -ENOMEM) { > + rc = kvm_s390_mmu_cache_topup(mc); If I'm not mistaken then gmap_link() -> dat_link() maps the possible -ENOMEM return value of dat_entry() to -EAGAIN. So the case where -ENOMEM leads to a kvm_s390_mmu_cache_topup() call will never happen.