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Tue, 14 Jan 2025 17:34:19 +0000 (GMT) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 14 Jan 2025 18:34:13 +0100 Message-Id: To: "Claudio Imbrenda" , Subject: Re: [PATCH v1 03/13] KVM: s390: use __kvm_faultin_pfn() From: "Christoph Schlameuss" Cc: , , , , , , , , , , X-Mailer: aerc 0.18.2 References: <20250108181451.74383-1-imbrenda@linux.ibm.com> <20250108181451.74383-4-imbrenda@linux.ibm.com> In-Reply-To: <20250108181451.74383-4-imbrenda@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 0RMxoIUluzqHNTirAazitC6qlxoNK_AS X-Proofpoint-GUID: 0RMxoIUluzqHNTirAazitC6qlxoNK_AS X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 lowpriorityscore=0 mlxscore=0 malwarescore=0 impostorscore=0 spamscore=0 bulkscore=0 mlxlogscore=999 phishscore=0 priorityscore=1501 clxscore=1015 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501140134 On Wed Jan 8, 2025 at 7:14 PM CET, Claudio Imbrenda wrote: > Refactor the existing page fault handling code to use __kvm_faultin_pfn()= . > > This possible now that memslots are always present. > > Signed-off-by: Claudio Imbrenda > --- > arch/s390/kvm/kvm-s390.c | 92 +++++++++++++++++++++++++++++++--------- > arch/s390/mm/gmap.c | 1 + > 2 files changed, 73 insertions(+), 20 deletions(-) With nits resolved: Reviewed-by: Christoph Schlameuss > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index 797b8503c162..8e4e7e45238b 100644 > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c > @@ -4794,11 +4794,66 @@ static void kvm_s390_assert_primary_as(struct kvm= _vcpu *vcpu) > current->thread.gmap_int_code, current->thread.gmap_teid.val); > } > =20 > +static int kvm_s390_handle_dat_fault(struct kvm_vcpu *vcpu, gfn_t gfn, g= pa_t gaddr, > + unsigned int flags) > +{ > + struct kvm_memory_slot *slot; > + unsigned int fault_flags; > + bool writable, unlocked; > + unsigned long vmaddr; > + struct page *page; > + kvm_pfn_t pfn; > + int rc; > + > + slot =3D kvm_vcpu_gfn_to_memslot(vcpu, gfn); > + if (!slot || slot->flags & KVM_MEMSLOT_INVALID) > + return vcpu_post_run_addressing_exception(vcpu); > + > + fault_flags =3D flags & FOLL_WRITE ? FAULT_FLAG_WRITE : 0; > + if (vcpu->arch.gmap->pfault_enabled) > + flags |=3D FOLL_NOWAIT; > + vmaddr =3D __gfn_to_hva_memslot(slot, gfn); > + > +try_again: > + pfn =3D __kvm_faultin_pfn(slot, gfn, flags, &writable, &page); > + > + /* Access outside memory, inject addressing exception */ > + if (is_noslot_pfn(pfn)) > + return vcpu_post_run_addressing_exception(vcpu); > + /* Signal pending: try again */ > + if (pfn =3D=3D KVM_PFN_ERR_SIGPENDING) > + return -EAGAIN; > + > + /* Needs I/O, try to setup async pfault (only possible with FOLL_NOWAIT= ) */ > + if (pfn =3D=3D KVM_PFN_ERR_NEEDS_IO) { > + trace_kvm_s390_major_guest_pfault(vcpu); > + if (kvm_arch_setup_async_pf(vcpu)) > + return 0; > + vcpu->stat.pfault_sync++; > + /* Could not setup async pfault, try again synchronously */ > + flags &=3D ~FOLL_NOWAIT; > + goto try_again; > + } > + /* Any other error */ > + if (is_error_pfn(pfn)) > + return -EFAULT; > + > + /* Success */ > + mmap_read_lock(vcpu->arch.gmap->mm); > + /* Mark the userspace PTEs as young and/or dirty, to avoid page fault l= oops */ > + rc =3D fixup_user_fault(vcpu->arch.gmap->mm, vmaddr, fault_flags, &unlo= cked); > + if (!rc) > + rc =3D __gmap_link(vcpu->arch.gmap, gaddr, vmaddr); > + kvm_release_faultin_page(vcpu->kvm, page, false, writable); > + mmap_read_unlock(vcpu->arch.gmap->mm); > + return rc; > +} > + > static int vcpu_post_run_handle_fault(struct kvm_vcpu *vcpu) > { > + unsigned long gaddr, gaddr_tmp; > unsigned int flags =3D 0; > - unsigned long gaddr; > - int rc =3D 0; > + gfn_t gfn; > =20 > gaddr =3D current->thread.gmap_teid.addr * PAGE_SIZE; > if (kvm_s390_cur_gmap_fault_is_write()) > @@ -4850,29 +4905,26 @@ static int vcpu_post_run_handle_fault(struct kvm_= vcpu *vcpu) > case PGM_REGION_SECOND_TRANS: > case PGM_REGION_THIRD_TRANS: > kvm_s390_assert_primary_as(vcpu); > - if (vcpu->arch.gmap->pfault_enabled) { > - rc =3D gmap_fault(vcpu->arch.gmap, gaddr, flags | FAULT_FLAG_RETRY_NO= WAIT); > - if (rc =3D=3D -EFAULT) > - return vcpu_post_run_addressing_exception(vcpu); > - if (rc =3D=3D -EAGAIN) { > - trace_kvm_s390_major_guest_pfault(vcpu); > - if (kvm_arch_setup_async_pf(vcpu)) > - return 0; > - vcpu->stat.pfault_sync++; > - } else { > - return rc; > - } > - } > - rc =3D gmap_fault(vcpu->arch.gmap, gaddr, flags); > - if (rc =3D=3D -EFAULT) { > - if (kvm_is_ucontrol(vcpu->kvm)) { > + > + gfn =3D gpa_to_gfn(gaddr); > + if (kvm_is_ucontrol(vcpu->kvm)) { > + /* > + * This translates the per-vCPU guest address into a > + * fake guest address, which can then be used with the > + * fake memslots that are identity mapping userspace. > + * This allows ucontrol VMs to use the normal fault > + * resolution path, like normal VMs. > + */ > + gaddr_tmp =3D gmap_translate(vcpu->arch.gmap, gaddr); > + if (gaddr_tmp =3D=3D -EFAULT) { > vcpu->run->exit_reason =3D KVM_EXIT_S390_UCONTROL; > vcpu->run->s390_ucontrol.trans_exc_code =3D gaddr; > vcpu->run->s390_ucontrol.pgm_code =3D 0x10; nit: s/0x10/PGM_SEGMENT_TRANSLATION/ > return -EREMOTE; > } > - return vcpu_post_run_addressing_exception(vcpu); > + gfn =3D gpa_to_gfn(gaddr_tmp); > } > + return kvm_s390_handle_dat_fault(vcpu, gfn, gaddr, flags); > break; nit: Remove the break after the return here? > default: > KVM_BUG(1, vcpu->kvm, "Unexpected program interrupt 0x%x, TEID 0x%016l= x", > @@ -4880,7 +4932,7 @@ static int vcpu_post_run_handle_fault(struct kvm_vc= pu *vcpu) > send_sig(SIGSEGV, current, 0); > break; > } > - return rc; > + return 0; > } > =20 > static int vcpu_post_run(struct kvm_vcpu *vcpu, int exit_reason) > diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c > index 16b8a36c56de..3aacef77c174 100644 > --- a/arch/s390/mm/gmap.c > +++ b/arch/s390/mm/gmap.c > @@ -605,6 +605,7 @@ int __gmap_link(struct gmap *gmap, unsigned long gadd= r, unsigned long vmaddr) > radix_tree_preload_end(); > return rc; > } > +EXPORT_SYMBOL(__gmap_link); > =20 > /** > * fixup_user_fault_nowait - manually resolve a user page fault without = waiting