Re: [Qemu-devel] [PATCH v5 34/36] spapr: add KVM support to the 'dual' machine

[Cédric Le Goater]

On 11/29/18 5:22 AM, David Gibson wrote:
> On Fri, Nov 16, 2018 at 11:57:27AM +0100, Cédric Le Goater wrote:
>> The interrupt mode is chosen by the CAS negotiation process and
>> activated after a reset to take into account the required changes in
>> the machine. This brings new constraints on how the associated KVM IRQ
>> device is initialized.
>>
>> Currently, each model takes care of the initialization of the KVM
>> device in their realize method but this is not possible anymore as the
>> initialization needs to done globaly when the interrupt mode is known,
>> i.e. when machine is reseted. It also means that we need a way to
>> delete a KVM device when another mode is chosen.
>>
>> Also, to support migration, the QEMU objects holding the state to
>> transfer should always be available but not necessarily activated.
>>
>> The overall approach of this proposal is to initialize both interrupt
>> mode at the QEMU level and keep the IRQ number space in sync to allow
>> switching from one mode to another. For the KVM side of things, the
>> whole initialization of the KVM device, sources and presenters, is
>> grouped in a single routine. The XICS and XIVE sPAPR IRQ reset
>> handlers are modified accordingly to handle the init and delete
>> sequences of the KVM device. The post_load handlers also are, to take
>> into account a possible change of interrupt mode after transfer.
>>
>> As KVM is now initialized at reset, we loose the possiblity to
>> fallback to the QEMU emulated mode in case of failure and failures
>> become fatal to the machine.
>>
>> Signed-off-by: Cédric Le Goater <address@hidden>
>> ---
>>  hw/intc/spapr_xive_kvm.c | 48 +++++++++++-----------
>>  hw/intc/xics_kvm.c       | 18 ++++++---
>>  hw/ppc/spapr_irq.c       | 86 +++++++++++++++++++++++++++++-----------
>>  3 files changed, 98 insertions(+), 54 deletions(-)
>>
>> diff --git a/hw/intc/spapr_xive_kvm.c b/hw/intc/spapr_xive_kvm.c
>> index 0672d8bcbc6b..9c7d36f51e3d 100644
>> --- a/hw/intc/spapr_xive_kvm.c
>> +++ b/hw/intc/spapr_xive_kvm.c
>> @@ -148,7 +148,6 @@ static void xive_tctx_kvm_init(XiveTCTX *tctx, Error 
>> **errp)
>>  
>>  static void xive_tctx_kvm_realize(DeviceState *dev, Error **errp)
>>  {
>> -    XiveTCTX *tctx = XIVE_TCTX_KVM(dev);
>>      XiveTCTXClass *xtc = XIVE_TCTX_BASE_GET_CLASS(dev);
>>      Error *local_err = NULL;
>>  
>> @@ -157,12 +156,6 @@ static void xive_tctx_kvm_realize(DeviceState *dev, 
>> Error **errp)
>>          error_propagate(errp, local_err);
>>          return;
>>      }
>> -
>> -    xive_tctx_kvm_init(tctx, &local_err);
>> -    if (local_err) {
>> -        error_propagate(errp, local_err);
>> -        return;
>> -    }
>>  }
>>  
>>  static void xive_tctx_kvm_class_init(ObjectClass *klass, void *data)
>> @@ -222,12 +215,9 @@ static void xive_source_kvm_init(XiveSource *xsrc, 
>> Error **errp)
>>  
>>  static void xive_source_kvm_reset(DeviceState *dev)
>>  {
>> -    XiveSource *xsrc = XIVE_SOURCE_KVM(dev);
>>      XiveSourceClass *xsc = XIVE_SOURCE_BASE_GET_CLASS(dev);
>>  
>>      xsc->parent_reset(dev);
>> -
>> -    xive_source_kvm_init(xsrc, &error_fatal);
>>  }
>>  
>>  /*
>> @@ -346,12 +336,6 @@ static void xive_source_kvm_realize(DeviceState *dev, 
>> Error **errp)
>>  
>>      xsrc->qirqs = qemu_allocate_irqs(xive_source_kvm_set_irq, xsrc,
>>                                       xsrc->nr_irqs);
>> -
>> -    xive_source_kvm_mmap(xsrc, &local_err);
>> -    if (local_err) {
>> -        error_propagate(errp, local_err);
>> -        return;
>> -    }
>>  }
>>  
>>  static void xive_source_kvm_unrealize(DeviceState *dev, Error **errp)
>> @@ -823,6 +807,7 @@ void spapr_xive_kvm_init(sPAPRXive *xive, Error **errp)
>>  {
>>      Error *local_err = NULL;
>>      size_t tima_len;
>> +    CPUState *cs;
>>  
>>      if (!kvm_enabled() || !kvmppc_has_cap_xive()) {
>>          error_setg(errp,
>> @@ -850,7 +835,18 @@ void spapr_xive_kvm_init(sPAPRXive *xive, Error **errp)
>>          return;
>>      }
>>  
>> -    /* Let the XiveSource KVM model handle the mapping for the moment */
>> +    xive_source_kvm_mmap(&xive->source, &local_err);
>> +    if (local_err) {
>> +        error_propagate(errp, local_err);
>> +        return;
>> +    }
>> +
>> +    /* Create the KVM interrupt sources */
>> +    xive_source_kvm_init(&xive->source, &local_err);
>> +    if (local_err) {
>> +        error_propagate(errp, local_err);
>> +        return;
>> +    }
>>  
>>      /* TIMA KVM mapping
>>       *
>> @@ -869,6 +865,17 @@ void spapr_xive_kvm_init(sPAPRXive *xive, Error **errp)
>>                                        "xive.tima", tima_len, xive->tm_mmap);
>>      sysbus_init_mmio(SYS_BUS_DEVICE(xive), &xive->tm_mmio);
>>  
>> +    /* Connect the presenters to the VCPU */
>> +    CPU_FOREACH(cs) {
>> +        PowerPCCPU *cpu = POWERPC_CPU(cs);
>> +
>> +        xive_tctx_kvm_init(XIVE_TCTX_BASE(cpu->intc), &local_err);
>> +        if (local_err) {
>> +            error_propagate(errp, local_err);
>> +            return;
>> +        }
>> +    }
>> +
>>      kvm_kernel_irqchip = true;
>>      kvm_msi_via_irqfd_allowed = true;
>>      kvm_gsi_direct_mapping = true;
>> @@ -920,16 +927,9 @@ void spapr_xive_kvm_fini(sPAPRXive *xive, Error **errp)
>>  
>>  static void spapr_xive_kvm_realize(DeviceState *dev, Error **errp)
>>  {
>> -    sPAPRXive *xive = SPAPR_XIVE_KVM(dev);
>>      sPAPRXiveClass *sxc = SPAPR_XIVE_BASE_GET_CLASS(dev);
>>      Error *local_err = NULL;
>>  
>> -    spapr_xive_kvm_init(xive, &local_err);
>> -    if (local_err) {
>> -        error_propagate(errp, local_err);
>> -        return;
>> -    }
>> -
>>      /* Initialize the source and the local routing tables */
>>      sxc->parent_realize(dev, &local_err);
>>      if (local_err) {
>> diff --git a/hw/intc/xics_kvm.c b/hw/intc/xics_kvm.c
>> index a7e3ec32a761..c89fa943847c 100644
>> --- a/hw/intc/xics_kvm.c
>> +++ b/hw/intc/xics_kvm.c
>> @@ -190,12 +190,6 @@ static void icp_kvm_realize(DeviceState *dev, Error 
>> **errp)
>>          error_propagate(errp, local_err);
>>          return;
>>      }
>> -
>> -    icp_kvm_init(ICP(dev), &local_err);
>> -    if (local_err) {
>> -        error_propagate(errp, local_err);
>> -        return;
>> -    }
>>  }
>>  
>>  static void icp_kvm_class_init(ObjectClass *klass, void *data)
>> @@ -427,6 +421,8 @@ static void rtas_dummy(PowerPCCPU *cpu, 
>> sPAPRMachineState *spapr,
>>  int xics_kvm_init(sPAPRMachineState *spapr, Error **errp)
>>  {
>>      int rc;
>> +    CPUState *cs;
>> +    Error *local_err = NULL;
>>  
>>      if (!kvm_enabled() || !kvm_check_extension(kvm_state, 
>> KVM_CAP_IRQ_XICS)) {
>>          error_setg(errp,
>> @@ -475,6 +471,16 @@ int xics_kvm_init(sPAPRMachineState *spapr, Error 
>> **errp)
>>      kvm_msi_via_irqfd_allowed = true;
>>      kvm_gsi_direct_mapping = true;
>>  
>> +    /* Connect the presenters to the VCPU */
>> +    CPU_FOREACH(cs) {
>> +        PowerPCCPU *cpu = POWERPC_CPU(cs);
>> +
>> +        icp_kvm_init(ICP(cpu->intc), &local_err);
>> +        if (local_err) {
>> +            error_propagate(errp, local_err);
>> +            goto fail;
>> +        }
>> +    }
>>      return 0;
>>  
>>  fail:
>> diff --git a/hw/ppc/spapr_irq.c b/hw/ppc/spapr_irq.c
>> index 79ead51c630d..f1720a8dda33 100644
>> --- a/hw/ppc/spapr_irq.c
>> +++ b/hw/ppc/spapr_irq.c
>> @@ -98,20 +98,14 @@ static void spapr_irq_init_xics(sPAPRMachineState 
>> *spapr, int nr_irqs,
>>      MachineState *machine = MACHINE(spapr);
>>      Error *local_err = NULL;
>>  
>> -    if (kvm_enabled()) {
>> -        if (machine_kernel_irqchip_allowed(machine) &&
>> -            !xics_kvm_init(spapr, &local_err)) {
>> -            spapr->icp_type = TYPE_KVM_ICP;
>> -            spapr->ics = spapr_ics_create(spapr, TYPE_ICS_KVM, nr_irqs,
>> -                                          &local_err);
>> -        }
>> -        if (machine_kernel_irqchip_required(machine) && !spapr->ics) {
>> -            error_prepend(&local_err,
>> -                          "kernel_irqchip requested but unavailable: ");
>> -            goto error;
>> +    if (kvm_enabled() && machine_kernel_irqchip_allowed(machine)) {
>> +        spapr->icp_type = TYPE_KVM_ICP;
>> +        spapr->ics = spapr_ics_create(spapr, TYPE_ICS_KVM, nr_irqs,
>> +                                      &local_err);
>> +        if (local_err) {
>> +            error_propagate(errp, local_err);
>> +            return;
>>          }
>> -        error_free(local_err);
>> -        local_err = NULL;
>>      }
>>  
>>      if (!spapr->ics) {
>> @@ -119,10 +113,11 @@ static void spapr_irq_init_xics(sPAPRMachineState 
>> *spapr, int nr_irqs,
>>          spapr->icp_type = TYPE_ICP;
>>          spapr->ics = spapr_ics_create(spapr, TYPE_ICS_SIMPLE, nr_irqs,
>>                                        &local_err);
>> +        if (local_err) {
>> +            error_propagate(errp, local_err);
>> +            return;
>> +        }
>>      }
>> -
>> -error:
>> -    error_propagate(errp, local_err);
>>  }
>>  
>>  #define ICS_IRQ_FREE(ics, srcno)   \
>> @@ -218,11 +213,28 @@ static int spapr_irq_post_load_xics(sPAPRMachineState 
>> *spapr, int version_id)
>>  
>>  static void spapr_irq_reset_xics(sPAPRMachineState *spapr, Error **errp)
>>  {
>> +    MachineState *machine = MACHINE(spapr);
>>      CPUState *cs;
>> +    Error *local_err = NULL;
>>  
>>      CPU_FOREACH(cs) {
>>          spapr_cpu_core_set_intc(POWERPC_CPU(cs), spapr->icp_type);
>>      }
>> +
>> +    if (kvm_enabled() && machine_kernel_irqchip_allowed(machine)) {
> 
> Aren't both devices '_fini'-ed by the machine level reset handler,

This is it. May be you mean that we should destroy all KVM devices
at the machine level reset before calling the sPAPR IRQ reset 
handler, which would only do the KVM init ? 

I agree there is a bit too much of these _fini calls.


> why does it need a _fini here as well as an init?

Each single interrupt mode machine (xics, xive) starts from a clean 
KVM state by destroying the KVM device and recreating it at reset.

> 
>> +        xics_kvm_fini(spapr, &local_err);
>> +        if (local_err) {
>> +            error_propagate(errp, local_err);
>> +            error_prepend(errp, "KVM XICS fini failed: ");
>> +            return;
>> +        }
>> +        xics_kvm_init(spapr, &local_err);
>> +        if (local_err) {
>> +            error_propagate(errp, local_err);
>> +            error_prepend(errp, "KVM XICS init failed: ");
>> +            return;
>> +        }
>> +    }
>>  }
>>  
>>  #define SPAPR_IRQ_XICS_NR_IRQS     0x1000
>> @@ -288,10 +300,8 @@ static void spapr_irq_init_xive(sPAPRMachineState 
>> *spapr, int nr_irqs,
>>          spapr->xive_tctx_type = TYPE_XIVE_TCTX_KVM;
>>          spapr->xive = spapr_xive_create(spapr, TYPE_SPAPR_XIVE_KVM, nr_irqs,
>>                                          nr_servers, &local_err);
>> -
>> -        if (local_err && machine_kernel_irqchip_required(machine)) {
>> +        if (local_err) {
>>              error_propagate(errp, local_err);
>> -            error_prepend(errp, "kernel_irqchip requested but init failed : 
>> ");
>>              return;
>>          }
>>  
>> @@ -375,12 +385,29 @@ static int spapr_irq_post_load_xive(sPAPRMachineState 
>> *spapr, int version_id)
>>  
>>  static void spapr_irq_reset_xive(sPAPRMachineState *spapr, Error **errp)
>>  {
>> +    MachineState *machine = MACHINE(spapr);
>>      CPUState *cs;
>> +    Error *local_err = NULL;
>>  
>>      CPU_FOREACH(cs) {
>>          spapr_cpu_core_set_intc(POWERPC_CPU(cs), spapr->xive_tctx_type);
>>      }
>>  
>> +    if (kvm_enabled() && machine_kernel_irqchip_allowed(machine)) {
>> +        spapr_xive_kvm_fini(spapr->xive, &local_err);
>> +        if (local_err) {
>> +            error_propagate(errp, local_err);
>> +            error_prepend(errp, "KVM XIVE fini failed: ");
>> +            return;
>> +        }
>> +        spapr_xive_kvm_init(spapr->xive, &local_err);
>> +        if (local_err) {
>> +            error_propagate(errp, local_err);
>> +            error_prepend(errp, "KVM XIVE init failed: ");
>> +            return;
>> +        }
>> +    }
>> +
>>      spapr_xive_mmio_map(spapr->xive);
>>  }
>>  
>> @@ -432,11 +459,6 @@ static void spapr_irq_init_dual(sPAPRMachineState 
>> *spapr, int nr_irqs,
>>  {
>>      Error *local_err = NULL;
>>  
>> -    if (kvm_enabled()) {
>> -        error_setg(errp, "No KVM support for the 'dual' machine");
>> -        return;
>> -    }
>> -
>>      spapr_irq_xics.init(spapr, spapr_irq_xics.nr_irqs, nr_servers, 
>> &local_err);
>>      if (local_err) {
>>          error_propagate(errp, local_err);
>> @@ -510,10 +532,15 @@ static Object 
>> *spapr_irq_cpu_intc_create_dual(sPAPRMachineState *spapr,
>>  
>>  static int spapr_irq_post_load_dual(sPAPRMachineState *spapr, int 
>> version_id)
>>  {
>> +    MachineState *machine = MACHINE(spapr);
>> +
>>      /*
>>       * Force a reset of the XIVE backend after migration.
>>       */
>>      if (spapr_ovec_test(spapr->ov5_cas, OV5_XIVE_EXPLOIT)) {
>> +        if (kvm_enabled() && machine_kernel_irqchip_allowed(machine)) {
>> +            xics_kvm_fini(spapr, &error_fatal);
>> +        }
>>          spapr_irq_xive.reset(spapr, &error_fatal);
>>      }
>>  
>> @@ -522,6 +549,17 @@ static int spapr_irq_post_load_dual(sPAPRMachineState 
>> *spapr, int version_id)
>>  
>>  static void spapr_irq_reset_dual(sPAPRMachineState *spapr, Error **errp)
>>  {
>> +    MachineState *machine = MACHINE(spapr);
>> +
>> +    /*
>> +     * Destroy all the KVM IRQ devices. This also clears the VCPU
>> +     * presenters
>> +     */
>> +    if (kvm_enabled() && machine_kernel_irqchip_allowed(machine)) {
>> +        xics_kvm_fini(spapr, &error_fatal);
>> +        spapr_xive_kvm_fini(spapr->xive, &error_fatal);
>> +    }
>> +
>>      /*
>>       * Only XICS is reseted at startup as it is the default interrupt
>>       * mode.
>