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Tue, 30 Sep 2025 18:02:58 -0700 (PDT) From: salil.mehta@opnsrc.net To: qemu-devel@nongnu.org, qemu-arm@nongnu.org, mst@redhat.com Cc: salil.mehta@huawei.com, maz@kernel.org, jean-philippe@linaro.org, jonathan.cameron@huawei.com, lpieralisi@kernel.org, peter.maydell@linaro.org, richard.henderson@linaro.org, imammedo@redhat.com, armbru@redhat.com, andrew.jones@linux.dev, david@redhat.com, philmd@linaro.org, eric.auger@redhat.com, will@kernel.org, ardb@kernel.org, oliver.upton@linux.dev, pbonzini@redhat.com, gshan@redhat.com, rafael@kernel.org, borntraeger@linux.ibm.com, alex.bennee@linaro.org, gustavo.romero@linaro.org, npiggin@gmail.com, harshpb@linux.ibm.com, linux@armlinux.org.uk, darren@os.amperecomputing.com, ilkka@os.amperecomputing.com, vishnu@os.amperecomputing.com, gankulkarni@os.amperecomputing.com, karl.heubaum@oracle.com, miguel.luis@oracle.com, salil.mehta@opnsrc.net, zhukeqian1@huawei.com, wangxiongfeng2@huawei.com, wangyanan55@huawei.com, wangzhou1@hisilicon.com, linuxarm@huawei.com, jiakernel2@gmail.com, maobibo@loongson.cn, lixianglai@loongson.cn, shahuang@redhat.com, zhao1.liu@intel.com Subject: [PATCH RFC V6 20/24] target/arm/kvm: Write vCPU's state back to KVM on cold-reset Date: Wed, 1 Oct 2025 01:01:23 +0000 Message-Id: <20251001010127.3092631-21-salil.mehta@opnsrc.net> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20251001010127.3092631-1-salil.mehta@opnsrc.net> References: <20251001010127.3092631-1-salil.mehta@opnsrc.net> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" 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=2a00:1450:4864:20::42f; envelope-from=salil.mehta@opnsrc.net; helo=mail-wr1-x42f.google.com X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, DKIM_INVALID=0.1, DKIM_SIGNED=0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: 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 @opnsrc.net) X-ZM-MESSAGEID: 1759281347585116600 From: Jean-Philippe Brucker Previously, all `PSCI_CPU_{ON, OFF}` calls were handled directly by KVM. However, with the introduction of this new vCPU hotplug-like feature, these hypervisor calls are now trapped to QEMU for policy checks. This shift can = lead to inconsistent vCPU states between KVM and QEMU, particularly when the vCP= U has been recently administratively enabled and is transitioning from either unp= arked state in QOM due to 'lazy realization' or even from 'powered-off' state. Therefore, it is crucial to synchronize the vCPU state with KVM, especially= in the context of a cold reset of the QOM vCPU. The same applies when PSCI CPU= _OFF is being handled by Qemu, it must ensure that kVM vCPUs are powered-off as = well. To ensure this synchronization, mark the QOM vCPU as "dirty" to trigger a c= all to `kvm_arch_put_registers()`. This guarantees that KVM=E2=80=99s `MP_STATE= ` is updated accordingly, forcing synchronization of the `mp_state` between QEMU and KVM. Signed-off-by: Jean-Philippe Brucker Signed-off-by: Salil Mehta --- target/arm/arm-powerctl.c | 1 + target/arm/kvm.c | 7 +++++++ 2 files changed, 8 insertions(+) diff --git a/target/arm/arm-powerctl.c b/target/arm/arm-powerctl.c index ab4422b261..89074918a9 100644 --- a/target/arm/arm-powerctl.c +++ b/target/arm/arm-powerctl.c @@ -263,6 +263,7 @@ static void arm_set_cpu_off_async_work(CPUState *target= _cpu_state, =20 assert(bql_locked()); target_cpu->power_state =3D PSCI_OFF; + target_cpu_state->vcpu_dirty =3D true; target_cpu_state->halted =3D 1; target_cpu_state->exception_index =3D EXCP_HLT; } diff --git a/target/arm/kvm.c b/target/arm/kvm.c index 98eb6db9ed..c4b68a0b17 100644 --- a/target/arm/kvm.c +++ b/target/arm/kvm.c @@ -1026,6 +1026,7 @@ bool kvm_arm_cpu_post_load(ARMCPU *cpu) void kvm_arm_reset_vcpu(ARMCPU *cpu) { int ret; + CPUState *cs =3D CPU(cpu); =20 /* Re-init VCPU so that all registers are set to * their respective reset values. @@ -1047,6 +1048,12 @@ void kvm_arm_reset_vcpu(ARMCPU *cpu) * for the same reason we do so in kvm_arch_get_registers(). */ write_list_to_cpustate(cpu); + + /* + * Ensure we call kvm_arch_put_registers(). The vCPU isn't marked dirt= y if + * it was parked in KVM and is now booting from a PSCI CPU_ON call. + */ + cs->vcpu_dirty =3D true; } =20 void kvm_arm_create_host_vcpu(ARMCPU *cpu) --=20 2.34.1