Re: [Qemu-devel] [PATCH 4/4] xics: Support for in-kernel XICS interrupt controller

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 08/01/2013 05:52 AM, Andreas Färber wrote:
> Hi,
> 
> Am 17.07.2013 08:37, schrieb Alexey Kardashevskiy:
>> From: David Gibson <david@gibson.dropbear.id.au>
>>
>> Recent (host) kernels support emulating the PAPR defined "XICS" interrupt
>> controller system within KVM.  This patch allows qemu to initialize and
>> configure the in-kernel XICS, and keep its state in sync with qemu's XICS
>> state as necessary.
>>
>> This should give considerable performance improvements.  e.g. on a simple
>> IPI ping-pong test between hardware threads, using qemu XICS gives us
>> around 5,000 irqs/second, whereas the in-kernel XICS gives us around
>> 70,000 irqs/s on the same hardware configuration.
>>
>> [Mike Qiu <qiudayu@linux.vnet.ibm.com>: fixed mistype which caused ics_set_kvm_state() to fail]
>> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
>> [aik: moved to a separate device, reworked QOM]
>>
>> ---
>> Changes:
>> 2013/07/17:
>> * QOM rework
>>
>> 2013/07/01
>> * fixed VMState names in order to support xics-kvm migration to xics and vice versa
>>
>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> 
> Something went wrong here. ;)


Yeah. git format-patch -s gets confused if commit message has parts
separated with '---' :)


> [...]
>> diff --git a/hw/intc/xics_kvm.c b/hw/intc/xics_kvm.c
>> new file mode 100644
>> index 0000000..04ce1be
>> --- /dev/null
>> +++ b/hw/intc/xics_kvm.c
> [...]
>> +typedef struct XICSStateKVM {
>> +    struct XICSState parent;
> 
> parent_obj to align with most new devices?
> 
>> +
>> +    uint32_t set_xive_token;
>> +    uint32_t get_xive_token;
>> +    uint32_t int_off_token;
>> +    uint32_t int_on_token;
>> +    int kernel_xics_fd;
>> +} XICSStateKVM;
> [...]
>> +static int ics_kvm_realize(DeviceState *dev)
>> +{
>> +    ICSState *ics = ICS(dev);
>> +
>> +    ics->irqs = g_malloc0(ics->nr_irqs * sizeof(ICSIRQState));
>> +    ics->islsi = g_malloc0(ics->nr_irqs * sizeof(bool));
>> +    ics->qirqs = qemu_allocate_irqs(ics_kvm_set_irq, ics, ics->nr_irqs);
>> +
>> +    return 0;
>> +}
>> +
>> +static void ics_kvm_class_init(ObjectClass *klass, void *data)
>> +{
>> +    DeviceClass *dc = DEVICE_CLASS(klass);
>> +    ICSStateClass *k = ICS_CLASS(klass);
>> +
>> +    dc->init = ics_kvm_realize;
> 
> This is fishy - probably you want to assign to dc->realize and fix the
> signature?
> 
> Andreas
> 
>> +    dc->reset = ics_kvm_reset;
>> +    k->pre_save = ics_get_kvm_state;
>> +    k->post_load = ics_set_kvm_state;
>> +}
>> +
>> +static TypeInfo ics_kvm_info = {
> 
> static const for all TypeInfos.
> 
>> +    .name = TYPE_ICS_KVM,
>> +    .parent = TYPE_ICS,
>> +    .instance_size = sizeof(ICSState),
>> +    .class_init = ics_kvm_class_init,
>> +};
>> +
>> +/*
>> + * XICS-KVM
>> + */
>> +static void xics_kvm_cpu_setup(XICSState *icp, PowerPCCPU *cpu)
>> +{
>> +    CPUState *cs;
>> +    ICPState *ss;
>> +    XICSStateKVM *icpkvm = (XICSStateKVM *) object_dynamic_cast(
>> +            OBJECT(icp), TYPE_XICS_KVM);
>> +    XICSStateClass *xics_info = XICS_CLASS(object_class_by_name(TYPE_XICS));
> 
> Are you intentionally accessing that class by name rather than using
> XICS_GET_CLASS(icp), which allows the KVM variant to overwrite things?


This is KVM's CPU_setup(). I want to call non-KVM CPU_setup afterwards,
i.e. "call parent method". XICS_GET_CLASS will return XICS_KVM class but
not XICS, no?



>> +
>> +    if (!icpkvm) {
>> +        return;
>> +    }
>> +
>> +    cs = CPU(cpu);
>> +    ss = &icp->ss[cs->cpu_index];
>> +
>> +    assert(cs->cpu_index < icp->nr_servers);
>> +    if (icpkvm->kernel_xics_fd == -1) {
>> +        abort();
>> +    }
>> +
>> +    if (icpkvm->kernel_xics_fd != -1) {
>> +        int ret;
>> +        struct kvm_enable_cap xics_enable_cap = {
>> +            .cap = KVM_CAP_IRQ_XICS,
>> +            .flags = 0,
>> +            .args = {icpkvm->kernel_xics_fd, cs->cpu_index, 0, 0},
>> +        };
>> +
>> +        ss->cs = cs;
>> +
>> +        ret = kvm_vcpu_ioctl(ss->cs, KVM_ENABLE_CAP, &xics_enable_cap);
>> +        if (ret < 0) {
>> +            fprintf(stderr, "Unable to connect CPU%d to kernel XICS: %s\n",
>> +                    cs->cpu_index, strerror(errno));
> 
> error_report() in place of all fprintf(stderr, ...)? (without \n then)
> 
>> +            exit(1);
>> +        }
>> +    }
>> +
>> +    /* Call emulated XICS implementation for consistency */
>> +    assert(xics_info);
> 
> If you want to go safe, you could add assert(xics_info->cpu_setup).
> 
>> +    xics_info->cpu_setup(icp, cpu);
>> +}
>> +
>> +static void rtas_dummy(PowerPCCPU *cpu, sPAPREnvironment *spapr,
>> +                       uint32_t token,
>> +                       uint32_t nargs, target_ulong args,
>> +                       uint32_t nret, target_ulong rets)
>> +{
>> +    fprintf(stderr, "pseries: %s must never be called for in-kernel XICS\n",
>> +            __func__);
>> +}
>> +
>> +static void xics_kvm_realize(DeviceState *dev, Error **errp)
>> +{
>> +    XICSStateKVM *icpkvm = XICS_KVM(dev);
>> +    XICSState *icp = XICS(dev);
>> +    ICSState *ics;
>> +    QemuOptsList *list = qemu_find_opts("machine");
>> +    int i, rc;
>> +    struct kvm_create_device xics_create_device = {
>> +        .type = KVM_DEV_TYPE_XICS,
>> +        .flags = 0,
>> +    };
>> +
>> +    if (!kvm_enabled()) {
>> +        error_setg(errp, "KVM must be enabled for in-kernel XICS");
>> +        goto fail;
>> +    }
>> +
>> +    if (QTAILQ_EMPTY(&list->head) ||
>> +        !qemu_opt_get_bool(QTAILQ_FIRST(&list->head),
>> +                           "kernel_irqchip", true) ||
> 
> Is it safe to take a value from the first element in the list? Shouldn't
> merging -machine spapr,accel=kvm -machine kernel_irqchip=on be taken
> into account?
> 
>> +        !kvm_check_extension(kvm_state, KVM_CAP_IRQ_XICS)) {
>> +        error_setg(errp, "KVM must be enabled for in-kernel XICS");
>> +        return;
>> +    }
>> +
>> +    icpkvm->set_xive_token = spapr_rtas_register("ibm,set-xive", rtas_dummy);
>> +    icpkvm->get_xive_token = spapr_rtas_register("ibm,get-xive", rtas_dummy);
>> +    icpkvm->int_off_token = spapr_rtas_register("ibm,int-off", rtas_dummy);
>> +    icpkvm->int_on_token = spapr_rtas_register("ibm,int-on", rtas_dummy);
>> +
>> +    rc = kvmppc_define_rtas_token(icpkvm->set_xive_token, "ibm,set-xive");
>> +    if (rc < 0) {
>> +        error_setg(errp, "kvmppc_define_rtas_token: ibm,set-xive");
>> +        goto fail;
>> +    }
>> +
>> +    rc = kvmppc_define_rtas_token(icpkvm->get_xive_token, "ibm,get-xive");
>> +    if (rc < 0) {
>> +        error_setg(errp, "kvmppc_define_rtas_token: ibm,get-xive");
>> +        goto fail;
>> +    }
>> +
>> +    rc = kvmppc_define_rtas_token(icpkvm->int_on_token, "ibm,int-on");
>> +    if (rc < 0) {
>> +        error_setg(errp, "kvmppc_define_rtas_token: ibm,int-on");
>> +        goto fail;
>> +    }
>> +
>> +    rc = kvmppc_define_rtas_token(icpkvm->int_off_token, "ibm,int-off");
>> +    if (rc < 0) {
>> +        error_setg(errp, "kvmppc_define_rtas_token: ibm,int-off");
>> +        goto fail;
>> +    }
>> +
>> +    /* Create the kernel ICP */
>> +    rc = kvm_vm_ioctl(kvm_state, KVM_CREATE_DEVICE, &xics_create_device);
>> +    if (rc < 0) {
>> +        error_setg_errno(errp, -rc, "Error on KVM_CREATE_DEVICE for XICS");
>> +        goto fail;
>> +    }
>> +
>> +    icpkvm->kernel_xics_fd = xics_create_device.fd;
>> +
>> +    icp->ics = ICS(object_new(TYPE_ICS_KVM));
>> +    ics = icp->ics;
>> +    object_property_add_child(OBJECT(icp), "ics", OBJECT(icp->ics), NULL);
>> +
>> +    ics->nr_irqs = icp->nr_irqs;
>> +    ics->offset = XICS_IRQ_BASE;
>> +    ics->icp = icp;
>> +    qdev_init_nofail(DEVICE(ics));
> 
> Since this is in a realize function, please use
> object_property_set_bool(), which gives you access to the Error - to
> catch it you can use a local Error *err variable.
> 
>> +
>> +    icp->ss = g_malloc0(icp->nr_servers*sizeof(ICPState));
>> +    for (i = 0; i < icp->nr_servers; i++) {
>> +        char buffer[32];
>> +        object_initialize(&icp->ss[i], TYPE_ICP_KVM);
>> +        snprintf(buffer, sizeof(buffer), "icp[%d]", i);
>> +        object_property_add_child(OBJECT(icp), buffer, OBJECT(&icp->ss[i]), NULL);
>> +        qdev_init_nofail(DEVICE(&icp->ss[i]));
> 
> object_property_set_bool()


? Anthony did XICS refactoring recently and that has qdev_init_nofail().


> Where does icp->nr_servers come from?

Via properties in try_create_xics() (hw/ppc/spapr.c).

> Is there no way to split this into
> instance_init and realize?


Why would we want to split?



>> +    }
>> +    return;
>> +
>> +fail:
>> +    kvmppc_define_rtas_token(0, "ibm,set-xive");
>> +    kvmppc_define_rtas_token(0, "ibm,get-xive");
>> +    kvmppc_define_rtas_token(0, "ibm,int-on");
>> +    kvmppc_define_rtas_token(0, "ibm,int-off");
>> +    return;
>> +}
>> +
>> +static void xics_kvm_class_init(ObjectClass *oc, void *data)
>> +{
>> +    DeviceClass *dc = DEVICE_CLASS(oc);
>> +    XICSStateClass *k = XICS_CLASS(oc);
> 
> xsc?


Whyyyy? Many places keep using "k".


>> +
>> +    dc->realize = xics_kvm_realize;
>> +    k->cpu_setup = xics_kvm_cpu_setup;
>> +}
>> +
>> +static const TypeInfo xics_kvm_info = {
>> +    .name          = TYPE_XICS_KVM,
>> +    .parent        = TYPE_XICS,
>> +    .instance_size = sizeof(XICSStateKVM),
>> +    .class_init    = xics_kvm_class_init,
>> +};
>> +
>> +static void xics_kvm_register_types(void)
>> +{
>> +    type_register_static(&xics_kvm_info);
>> +    type_register_static(&ics_kvm_info);
>> +    type_register_static(&icp_kvm_info);
>> +}
>> +
>> +type_init(xics_kvm_register_types)
>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>> index 432f0d2..84433ee 100644
>> --- a/hw/ppc/spapr.c
>> +++ b/hw/ppc/spapr.c
>> @@ -148,7 +148,31 @@ static XICSState *xics_system_init(int nr_servers, int nr_irqs)
>>  {
>>      XICSState *icp = NULL;
>>  
>> -    icp = try_create_xics(TYPE_XICS, nr_servers, nr_irqs);
>> +    if (kvm_enabled()) {
>> +        bool irqchip_allowed = true, irqchip_required = false;
>> +        QemuOptsList *list = qemu_find_opts("machine");
>> +
>> +        if (!QTAILQ_EMPTY(&list->head)) {
>> +            irqchip_allowed = qemu_opt_get_bool(QTAILQ_FIRST(&list->head),
>> +                                                "kernel_irqchip", true);
>> +            irqchip_required = qemu_opt_get_bool(QTAILQ_FIRST(&list->head),
>> +                                                 "kernel_irqchip", false);
>> +        }
> 
> Again, don't we have APIs to help with opts access?


Hm, I copied this from openpic but it went further since then :)


>> +
>> +        if (irqchip_allowed) {
>> +            icp = try_create_xics(TYPE_XICS_KVM, nr_servers, nr_irqs);
>> +        }
>> +
>> +        if (irqchip_required && !icp) {
>> +            perror("iFailed to create in-kernel XICS\n");
> 
> "Failed to ..."?


vim...



-- 
Alexey