Re: [PATCH V3 01/10] accel/kvm: Extract common KVM vCPU {creation,parking} code

[David Hildenbrand <david@redhat.com>]

On 09.10.23 13:28, Salil Mehta wrote:
> KVM vCPU creation is done once during the initialization of the VM when Qemu
> thread is spawned. This is common to all the architectures.
> 
> Hot-unplug of vCPU results in destruction of the vCPU object in QOM but the
> corresponding KVM vCPU object in the Host KVM is not destroyed and its
> representative KVM vCPU object/context in Qemu is parked.
> 
> Refactor common logic so that some APIs could be reused by vCPU Hotplug code.
> 
> Signed-off-by: Salil Mehta <salil.mehta@huawei.com>

[...]

>   
>   int kvm_init_vcpu(CPUState *cpu, Error **errp)
> @@ -395,19 +434,14 @@ 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)",

Unrelated change.

>                            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/accel/kvm/trace-events b/accel/kvm/trace-events
> index 399aaeb0ec..08e2dc253f 100644
> --- a/accel/kvm/trace-events
> +++ b/accel/kvm/trace-events
> @@ -9,6 +9,10 @@ kvm_device_ioctl(int fd, int type, void *arg) "dev fd %d, type 0x%x, arg %p"
>   kvm_failed_reg_get(uint64_t id, const char *msg) "Warning: Unable to retrieve ONEREG %" PRIu64 " from KVM: %s"
>   kvm_failed_reg_set(uint64_t id, const char *msg) "Warning: Unable to set ONEREG %" PRIu64 " to KVM: %s"
>   kvm_init_vcpu(int cpu_index, unsigned long arch_cpu_id) "index: %d id: %lu"
> +kvm_create_vcpu(int cpu_index, unsigned long arch_cpu_id) "creating KVM cpu: cpu_index: %d arch vcpu-id: %lu"
> +kvm_get_vcpu(unsigned long arch_cpu_id) "unparking KVM vcpu: arch vcpu-id: %lu"
> +kvm_destroy_vcpu(int cpu_index, unsigned long arch_cpu_id) "destroy vcpu: cpu_index: %d arch vcpu-id: %lu"
> +kvm_park_vcpu(int cpu_index, unsigned long arch_cpu_id) "parking KVM vcpu: cpu_index: %d arch vcpu-id: %lu"

It's a bit confusing that there is now

1) create (create new or return parked)
2) destroy (cleanup + park)
3) park (park only)

Why would one use 2) instead of 3) or the other way around? But I 
suspect that kvm_destroy_vcpu() is only supposed to be a KVM-internal 
helper ...

>   kvm_irqchip_commit_routes(void) ""
>   kvm_irqchip_add_msi_route(char *name, int vector, int virq) "dev %s vector %d virq %d"
>   kvm_irqchip_update_msi_route(int virq) "Updating MSI route virq=%d"
> diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
> index ee9025f8e9..57bd8f8fd6 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 fetched/created.
> + *
> + * @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


^ I suspect that description is wrong.

-- 
Cheers,

David / dhildenb