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Wed, 11 Feb 2026 22:27:19 -0800 (PST) X-Received: by 2002:a17:90b:520e:b0:341:8491:472a with SMTP id 98e67ed59e1d1-3568f2e017fmr1860982a91.4.1770877639375; Wed, 11 Feb 2026 22:27:19 -0800 (PST) From: Ani Sinha To: "Michael S. Tsirkin" , Marcel Apfelbaum , Paolo Bonzini , Richard Henderson , Eduardo Habkost Cc: kraxel@redhat.com, Ani Sinha , qemu-devel@nongnu.org Subject: [PATCH v4 29/31] kvm/clock: add support for confidential guest reset Date: Thu, 12 Feb 2026 11:55:13 +0530 Message-ID: <20260212062522.99565-30-anisinha@redhat.com> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20260212062522.99565-1-anisinha@redhat.com> References: <20260212062522.99565-1-anisinha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=anisinha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1770877748964158500 Content-Type: text/plain; charset="utf-8" Confidential guests change the KVM VM file descriptor upon reset and also c= reate new VCPU file descriptors against the new KVM VM file descriptor. We need to save the clock state from kvm before KVM VM file descriptor changes and res= tore it after. Also after VCPU file descriptors changed, we must call KVM_KVMCLOCK_CTRL on the VCPU file descriptor to inform KVM that the VCPU is in paused state. Signed-off-by: Ani Sinha --- hw/i386/kvm/clock.c | 59 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c index aba6842a22..10d34254f0 100644 --- a/hw/i386/kvm/clock.c +++ b/hw/i386/kvm/clock.c @@ -50,6 +50,9 @@ struct KVMClockState { /* whether the 'clock' value was obtained in a host with * reliable KVM_GET_CLOCK */ bool clock_is_reliable; + + NotifierWithReturn kvmclock_vcpufd_change_notifier; + NotifierWithReturn kvmclock_vmfd_change_notifier; }; =20 struct pvclock_vcpu_time_info { @@ -63,6 +66,9 @@ struct pvclock_vcpu_time_info { uint8_t pad[2]; } __attribute__((__packed__)); /* 32 bytes */ =20 +static int kvmclock_set_clock(NotifierWithReturn *notifier, + void *data, Error** errp); + static uint64_t kvmclock_current_nsec(KVMClockState *s) { CPUState *cpu =3D first_cpu; @@ -219,6 +225,54 @@ static void kvmclock_vm_state_change(void *opaque, boo= l running, } } =20 +static int kvmclock_save_clock(NotifierWithReturn *notifier, + void *data, Error** errp) +{ + if (!((VmfdChangeNotifier *)data)->pre) { + return 0; + } + KVMClockState *s =3D container_of(notifier, KVMClockState, + kvmclock_vmfd_change_notifier); + kvm_update_clock(s); + return 0; +} + +static int kvmclock_set_clock(NotifierWithReturn *notifier, + void *data, Error** errp) +{ + struct kvm_clock_data clock_data =3D {}; + CPUState *cpu; + int ret; + KVMClockState *s =3D container_of(notifier, KVMClockState, + kvmclock_vcpufd_change_notifier); + int cap_clock_ctrl =3D kvm_check_extension(kvm_state, KVM_CAP_KVMCLOCK= _CTRL); + + if (!s->clock_is_reliable) { + uint64_t pvclock_via_mem =3D kvmclock_current_nsec(s); + /* saved clock value before vmfd change is not reliable */ + if (pvclock_via_mem) { + s->clock =3D pvclock_via_mem; + } + } + + clock_data.clock =3D s->clock; + ret =3D kvm_vm_ioctl(kvm_state, KVM_SET_CLOCK, &clock_data); + if (ret < 0) { + fprintf(stderr, "KVM_SET_CLOCK failed: %s\n", strerror(-ret)); + abort(); + } + + if (!cap_clock_ctrl) { + return 0; + } + CPU_FOREACH(cpu) { + run_on_cpu(cpu, do_kvmclock_ctrl, RUN_ON_CPU_NULL); + } + + return 0; +} + + static void kvmclock_realize(DeviceState *dev, Error **errp) { KVMClockState *s =3D KVM_CLOCK(dev); @@ -230,7 +284,12 @@ static void kvmclock_realize(DeviceState *dev, Error *= *errp) =20 kvm_update_clock(s); =20 + s->kvmclock_vcpufd_change_notifier.notify =3D kvmclock_set_clock; + s->kvmclock_vmfd_change_notifier.notify =3D kvmclock_save_clock; + qemu_add_vm_change_state_handler(kvmclock_vm_state_change, s); + kvm_vcpufd_add_change_notifier(&s->kvmclock_vcpufd_change_notifier); + kvm_vmfd_add_change_notifier(&s->kvmclock_vmfd_change_notifier); } =20 static bool kvmclock_clock_is_reliable_needed(void *opaque) --=20 2.42.0