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([2001:8003:e5b0:9f00:dbbc:1945:6e65:ec5]) by smtp.gmail.com with ESMTPSA id l5-20020a170902eb0500b001c619fbd5fbsm15971197plb.298.2023.10.02.16.17.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Oct 2023 16:17:54 -0700 (PDT) Message-ID: Date: Tue, 3 Oct 2023 09:17:41 +1000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH V2 01/10] accel/kvm: Extract common KVM vCPU {creation,parking} code Content-Language: en-US To: Salil Mehta , qemu-devel@nongnu.org, qemu-arm@nongnu.org Cc: 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, andrew.jones@linux.dev, david@redhat.com, philmd@linaro.org, eric.auger@redhat.com, oliver.upton@linux.dev, pbonzini@redhat.com, mst@redhat.com, will@kernel.org, rafael@kernel.org, alex.bennee@linaro.org, linux@armlinux.org.uk, darren@os.amperecomputing.com, ilkka@os.amperecomputing.com, vishnu@os.amperecomputing.com, karl.heubaum@oracle.com, miguel.luis@oracle.com, salil.mehta@opnsrc.net, zhukeqian1@huawei.com, wangxiongfeng2@huawei.com, wangyanan55@huawei.com, jiakernel2@gmail.com, maobibo@loongson.cn, lixianglai@loongson.cn, linuxarm@huawei.com References: <20230930001933.2660-1-salil.mehta@huawei.com> <20230930001933.2660-2-salil.mehta@huawei.com> From: Gavin Shan In-Reply-To: <20230930001933.2660-2-salil.mehta@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=gshan@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 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, NICE_REPLY_A=-2.321, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=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: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 9/30/23 10:19, Salil Mehta wrote: > KVM vCPU creation is done once during the initialization of the VM when Qemu > threads are spawned. This is common to all the architectures. ^^^^^^^^^^^^^^^^^^^ thread is spawned. > > Hot-unplug of vCPU results in destruction of the vCPU objects in QOM but > the KVM vCPU objects in the Host KVM are not destroyed and their representative > KVM vCPU objects/context in Qemu are parked. > > Refactor common logic so that some APIs could be reused by vCPU Hotplug code. > > Signed-off-by: Salil Mehta > --- > accel/kvm/kvm-all.c | 63 +++++++++++++++++++++++++++++++++----------- > include/sysemu/kvm.h | 14 ++++++++++ > 2 files changed, 61 insertions(+), 16 deletions(-) > > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c > index ff1578bb32..b8c36ba50a 100644 > --- a/accel/kvm/kvm-all.c > +++ b/accel/kvm/kvm-all.c > @@ -80,7 +80,7 @@ > #endif > > struct KVMParkedVcpu { > - unsigned long vcpu_id; > + int vcpu_id; @vcpu_id represents the vCPU index (CPUState::cpu_index) instead of the architectural CPU ID any more. However, I don't understand how it works for x86, and more comments regarding it can be seen below. > int kvm_fd; > QLIST_ENTRY(KVMParkedVcpu) node; > }; > @@ -137,6 +137,7 @@ static QemuMutex kml_slots_lock; > #define kvm_slots_unlock() qemu_mutex_unlock(&kml_slots_lock) > > static void kvm_slot_init_dirty_bitmap(KVMSlot *mem); > +static int kvm_get_vcpu(KVMState *s, int vcpu_id); > > static inline void kvm_resample_fd_remove(int gsi) > { > @@ -320,11 +321,49 @@ err: > return ret; > } > > +void kvm_park_vcpu(CPUState *cpu) > +{ > + int vcpu_id = cpu->cpu_index; > + struct KVMParkedVcpu *vcpu; > + > + vcpu = g_malloc0(sizeof(*vcpu)); > + vcpu->vcpu_id = vcpu_id; > + vcpu->kvm_fd = cpu->kvm_fd; > + QLIST_INSERT_HEAD(&kvm_state->kvm_parked_vcpus, vcpu, node); > +} > + @vcpu_id can be dropped as suggested previously. vcpu->vcpu_id = cpu->cpu_index; > +int kvm_create_vcpu(CPUState *cpu) > +{ > + int vcpu_id = cpu->cpu_index; > + KVMState *s = kvm_state; > + int kvm_fd; > + > + DPRINTF("kvm_create_vcpu\n"); > + > + /* check if the KVM vCPU already exist but is parked */ > + kvm_fd = kvm_get_vcpu(s, vcpu_id); > + if (kvm_fd < 0) { > + /* vCPU not parked: create a new KVM vCPU */ > + kvm_fd = kvm_vm_ioctl(s, KVM_CREATE_VCPU, vcpu_id); > + if (kvm_fd < 0) { > + error_report("KVM_CREATE_VCPU IOCTL failed for vCPU %d", vcpu_id); > + return kvm_fd; > + } > + } > + > + cpu->vcpu_dirty = true; > + cpu->kvm_fd = kvm_fd; > + cpu->kvm_state = s; > + cpu->dirty_pages = 0; > + cpu->throttle_us_per_full = 0; > + > + return 0; > +} > + The comments here can be dropped since the code is self-explaining. @vcpu_id represents vCPU index, instead of the architecrual vCPU ID any more. @vcpu_id is passed to host through ioctl(KVM_CREATE_VCPU), which is expected as an architecrual vCPU ID instead of a vCPU index by host. It's indicated by 'struct kvm_vcpu' as below. struct kvm_vcpu { : int vcpu_id; /* id given by userspace at creation */ int vcpu_idx; /* index into kvm->vcpu_array */ }; Function kvm_arch_vcpu_id() converts the vCPU instance or vCPU index to the architecrual vCPU ID. All architectures except x86 simply returns vCPU index (CPUState::cpu_index) as the architecrural vCPU ID. x86 returns the APIC ID. Treating them equally seems to break x86. > static int do_kvm_destroy_vcpu(CPUState *cpu) > { > KVMState *s = kvm_state; > long mmap_size; > - struct KVMParkedVcpu *vcpu = NULL; > int ret = 0; > > DPRINTF("kvm_destroy_vcpu\n"); > @@ -353,10 +392,7 @@ static int do_kvm_destroy_vcpu(CPUState *cpu) > } > } > > - vcpu = g_malloc0(sizeof(*vcpu)); > - vcpu->vcpu_id = kvm_arch_vcpu_id(cpu); > - vcpu->kvm_fd = cpu->kvm_fd; > - QLIST_INSERT_HEAD(&kvm_state->kvm_parked_vcpus, vcpu, node); > + kvm_park_vcpu(cpu); > err: > return ret; > } > @@ -369,7 +405,7 @@ void kvm_destroy_vcpu(CPUState *cpu) > } > } > > -static int kvm_get_vcpu(KVMState *s, unsigned long vcpu_id) > +static int kvm_get_vcpu(KVMState *s, int vcpu_id) > { > struct KVMParkedVcpu *cpu; > > @@ -384,7 +420,7 @@ static int kvm_get_vcpu(KVMState *s, unsigned long vcpu_id) > } > } > > - return kvm_vm_ioctl(s, KVM_CREATE_VCPU, (void *)vcpu_id); > + return -1; > } > Why we have -1 here. -ENOENT seems more descriptive? > int kvm_init_vcpu(CPUState *cpu, Error **errp) > @@ -395,19 +431,14 @@ int kvm_init_vcpu(CPUState *cpu, Error **errp) > > trace_kvm_init_vcpu(cpu->cpu_index, kvm_arch_vcpu_id(cpu)); > > - ret = kvm_get_vcpu(s, kvm_arch_vcpu_id(cpu)); > + ret = kvm_create_vcpu(cpu); > if (ret < 0) { > - error_setg_errno(errp, -ret, "kvm_init_vcpu: kvm_get_vcpu failed (%lu)", > + error_setg_errno(errp, -ret, > + "kvm_init_vcpu: kvm_create_vcpu failed (%lu)", > kvm_arch_vcpu_id(cpu)); > goto err; > } > > - cpu->kvm_fd = ret; > - cpu->kvm_state = s; > - cpu->vcpu_dirty = true; > - cpu->dirty_pages = 0; > - cpu->throttle_us_per_full = 0; > - > mmap_size = kvm_ioctl(s, KVM_GET_VCPU_MMAP_SIZE, 0); > if (mmap_size < 0) { > ret = mmap_size; > diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h > index ee9025f8e9..785f3ed083 100644 > --- a/include/sysemu/kvm.h > +++ b/include/sysemu/kvm.h > @@ -464,6 +464,20 @@ void kvm_set_sigmask_len(KVMState *s, unsigned int sigmask_len); > > int kvm_physical_memory_addr_from_host(KVMState *s, void *ram_addr, > hwaddr *phys_addr); > +/** > + * kvm_create_vcpu - Gets a parked KVM vCPU or creates a KVM vCPU > + * @cpu: QOM CPUState object for which KVM vCPU has to be created/fetched. > + * > + * @returns: 0 when success, errno (<0) when failed. > + */ > +int kvm_create_vcpu(CPUState *cpu); > +/** > + * kvm_park_vcpu - Gets a parked KVM vCPU if it exists > + * @cpu: QOM CPUState object for which parked KVM vCPU has to be fetched. > + * > + * @returns: kvm_fd (>0) when success, -1 when failed. > + */ > +void kvm_park_vcpu(CPUState *cpu); > > #endif /* NEED_CPU_H */ > Thanks, Gavin