Re: [PATCH v4 13/42] hw/pxb: Allow creation of a CXL PXB (host bridge)

[Jonathan Cameron via <qemu-devel@nongnu.org>]

On Thu, 27 Jan 2022 13:59:56 +0000
Alex Bennée <alex.bennee@linaro.org> wrote:

> Jonathan Cameron <Jonathan.Cameron@huawei.com> writes:
> 
> > From: Ben Widawsky <ben.widawsky@intel.com>
> >
> > This works like adding a typical pxb device, except the name is
> > 'pxb-cxl' instead of 'pxb-pcie'. An example command line would be as
> > follows:
> >   -device pxb-cxl,id=cxl.0,bus="pcie.0",bus_nr=1
> >
> > A CXL PXB is backward compatible with PCIe. What this means in practice
> > is that an operating system that is unaware of CXL should still be able
> > to enumerate this topology as if it were PCIe.
> >
> > One can create multiple CXL PXB host bridges, but a host bridge can only
> > be connected to the main root bus. Host bridges cannot appear elsewhere
> > in the topology.
> >
> > Note that as of this patch, the ACPI tables needed for the host bridge
> > (specifically, an ACPI object in _SB named ACPI0016 and the CEDT) aren't
> > created. So while this patch internally creates it, it cannot be
> > properly used by an operating system or other system software.
> >
> > Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> > Signed-off-by: Jonathan.Cameron <Jonathan.Cameron@huawei.com>
> > ---
> >  hw/pci-bridge/pci_expander_bridge.c | 98 ++++++++++++++++++++++++++++-
> >  hw/pci/pci.c                        |  7 +++
> >  include/hw/pci/pci.h                |  6 ++
> >  3 files changed, 109 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> > index a6caa1e7b5..7009b541de 100644
> > --- a/hw/pci-bridge/pci_expander_bridge.c
> > +++ b/hw/pci-bridge/pci_expander_bridge.c
> > @@ -17,6 +17,7 @@
> >  #include "hw/pci/pci_host.h"
> >  #include "hw/qdev-properties.h"
> >  #include "hw/pci/pci_bridge.h"
> > +#include "hw/cxl/cxl.h"
> >  #include "qemu/range.h"
> >  #include "qemu/error-report.h"
> >  #include "qemu/module.h"
> > @@ -56,6 +57,10 @@ DECLARE_INSTANCE_CHECKER(PXBDev, PXB_DEV,
> >  DECLARE_INSTANCE_CHECKER(PXBDev, PXB_PCIE_DEV,
> >                           TYPE_PXB_PCIE_DEVICE)
> >  
> > +#define TYPE_PXB_CXL_DEVICE "pxb-cxl"
> > +DECLARE_INSTANCE_CHECKER(PXBDev, PXB_CXL_DEV,
> > +                         TYPE_PXB_CXL_DEVICE)
> > +
> >  struct PXBDev {
> >      /*< private >*/
> >      PCIDevice parent_obj;
> > @@ -66,8 +71,19 @@ struct PXBDev {
> >      bool bypass_iommu;
> >  };
> >  
> > +typedef struct CXLHost {
> > +    PCIHostState parent_obj;
> > +
> > +    CXLComponentState cxl_cstate;
> > +} CXLHost;
> > +
> >  static PXBDev *convert_to_pxb(PCIDevice *dev)
> >  {
> > +    /* A CXL PXB's parent bus is PCIe, so the normal check won't work */
> > +    if (object_dynamic_cast(OBJECT(dev), TYPE_PXB_CXL_DEVICE)) {
> > +        return PXB_CXL_DEV(dev);
> > +    }
> > +
> >      return pci_bus_is_express(pci_get_bus(dev))
> >          ? PXB_PCIE_DEV(dev) : PXB_DEV(dev);
> >  }
> > @@ -76,6 +92,9 @@ static GList *pxb_dev_list;
> >  
> >  #define TYPE_PXB_HOST "pxb-host"
> >  
> > +#define TYPE_PXB_CXL_HOST "pxb-cxl-host"
> > +#define PXB_CXL_HOST(obj) OBJECT_CHECK(CXLHost, (obj), TYPE_PXB_CXL_HOST)
> > +
> >  static int pxb_bus_num(PCIBus *bus)
> >  {
> >      PXBDev *pxb = convert_to_pxb(bus->parent_dev);
> > @@ -112,11 +131,20 @@ static const TypeInfo pxb_pcie_bus_info = {
> >      .class_init    = pxb_bus_class_init,
> >  };
> >  
> > +static const TypeInfo pxb_cxl_bus_info = {
> > +    .name          = TYPE_PXB_CXL_BUS,
> > +    .parent        = TYPE_CXL_BUS,
> > +    .instance_size = sizeof(PXBBus),
> > +    .class_init    = pxb_bus_class_init,
> > +};
> > +
> >  static const char *pxb_host_root_bus_path(PCIHostState *host_bridge,
> >                                            PCIBus *rootbus)
> >  {
> > -    PXBBus *bus = pci_bus_is_express(rootbus) ?
> > -                  PXB_PCIE_BUS(rootbus) : PXB_BUS(rootbus);
> > +    PXBBus *bus = pci_bus_is_cxl(rootbus) ?
> > +                      PXB_CXL_BUS(rootbus) :
> > +                      pci_bus_is_express(rootbus) ? PXB_PCIE_BUS(rootbus) :
> > +                                                    PXB_BUS(rootbus);
> >  
> >      snprintf(bus->bus_path, 8, "0000:%02x", pxb_bus_num(rootbus));
> >      return bus->bus_path;
> > @@ -218,6 +246,16 @@ static int pxb_map_irq_fn(PCIDevice *pci_dev, int pin)
> >      return pin - PCI_SLOT(pxb->devfn);
> >  }
> >  
> > +static void pxb_dev_reset(DeviceState *dev)
> > +{
> > +    CXLHost *cxl = PXB_CXL_HOST(dev);
Having fixed the stuff you observed below...

It's not that device by rather the PXB_CXL_DEV and we
can access the CXLHost via
PXB_CXL_DEV(dv)->cxl.cxl_host_bridge()
at which point this seems to be working.

> > +    CXLComponentState *cxl_cstate = &cxl->cxl_cstate;
> > +    uint32_t *reg_state = cxl_cstate->crb.cache_mem_registers;
> > +
> > +    cxl_component_register_init_common(reg_state, CXL2_ROOT_PORT);
> > +    ARRAY_FIELD_DP32(reg_state, CXL_HDM_DECODER_CAPABILITY, TARGET_COUNT, 8);
> > +}
> > +
> >  static gint pxb_compare(gconstpointer a, gconstpointer b)
> >  {
> >      const PXBDev *pxb_a = a, *pxb_b = b;
> > @@ -290,6 +328,11 @@ static void pxb_dev_realize_common(PCIDevice *dev, enum BusType type,
> >      pci_config_set_class(dev->config, PCI_CLASS_BRIDGE_HOST);
> >  
> >      pxb_dev_list = g_list_insert_sorted(pxb_dev_list, pxb, pxb_compare);
> > +
> > +    if (type == CXL) {
> > +        pxb_dev_reset(ds);
> > +    }
> > +  
> 
> Couldn't this just be done in the cxl realize function after it calls the
> common code?
yup.

> 
> >      return;
> >  
> >  err_register_bus:
> > @@ -338,6 +381,12 @@ static void pxb_dev_class_init(ObjectClass *klass, void *data)
> >      device_class_set_props(dc, pxb_dev_properties);
> >      dc->hotpluggable = false;
> >      set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);
> > +
> > +    /*
> > +     * Reset doesn't seem to actually be called, but maybe it will in the
> > +     * future?
> > +     */
> > +    dc->reset = pxb_dev_reset;  
> 
> Surely because this should be in pxb_cxl_dev_class_init?

That would indeed do it.

Thanks.

Jonathan

> 
> >  }
> >  
> >  static const TypeInfo pxb_dev_info = {
> > @@ -389,13 +438,58 @@ static const TypeInfo pxb_pcie_dev_info = {
> >      },
> >  };
> >  
> > +static void pxb_cxl_dev_realize(PCIDevice *dev, Error **errp)
> > +{
> > +    /* A CXL PXB's parent bus is still PCIe */
> > +    if (!pci_bus_is_express(pci_get_bus(dev))) {
> > +        error_setg(errp, "pxb-cxl devices cannot reside on a PCI bus");
> > +        return;
> > +    }
> > +
> > +    pxb_dev_realize_common(dev, CXL, errp);
> > +}
> > +
> > +static void pxb_cxl_dev_class_init(ObjectClass *klass, void *data)
> > +{
> > +    DeviceClass *dc   = DEVICE_CLASS(klass);
> > +    PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
> > +
> > +    k->realize             = pxb_cxl_dev_realize;
> > +    k->exit                = pxb_dev_exitfn;
> > +    /*
> > +     * XXX: These types of bridges don't actually show up in the hierarchy so
> > +     * vendor, device, class, etc. ids are intentionally left out.
> > +     */
> > +
> > +    dc->desc = "CXL Host Bridge";
> > +    device_class_set_props(dc, pxb_dev_properties);
> > +    set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);
> > +
> > +    /* Host bridges aren't hotpluggable. FIXME: spec reference */
> > +    dc->hotpluggable = false;
> > +}
> > +
> > +static const TypeInfo pxb_cxl_dev_info = {
> > +    .name          = TYPE_PXB_CXL_DEVICE,
> > +    .parent        = TYPE_PCI_DEVICE,
> > +    .instance_size = sizeof(PXBDev),
> > +    .class_init    = pxb_cxl_dev_class_init,
> > +    .interfaces =
> > +        (InterfaceInfo[]){
> > +            { INTERFACE_CONVENTIONAL_PCI_DEVICE },
> > +            {},
> > +        },
> > +};
> > +
> >  static void pxb_register_types(void)
> >  {
> >      type_register_static(&pxb_bus_info);
> >      type_register_static(&pxb_pcie_bus_info);
> > +    type_register_static(&pxb_cxl_bus_info);
> >      type_register_static(&pxb_host_info);
> >      type_register_static(&pxb_dev_info);
> >      type_register_static(&pxb_pcie_dev_info);
> > +    type_register_static(&pxb_cxl_dev_info);
> >  }
> >  
> >  type_init(pxb_register_types)
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index 474ea98c1d..cafebf6f59 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -229,6 +229,12 @@ static const TypeInfo pcie_bus_info = {
> >      .class_init = pcie_bus_class_init,
> >  };
> >  
> > +static const TypeInfo cxl_bus_info = {
> > +    .name       = TYPE_CXL_BUS,
> > +    .parent     = TYPE_PCIE_BUS,
> > +    .class_init = pcie_bus_class_init,
> > +};
> > +
> >  static PCIBus *pci_find_bus_nr(PCIBus *bus, int bus_num);
> >  static void pci_update_mappings(PCIDevice *d);
> >  static void pci_irq_handler(void *opaque, int irq_num, int level);
> > @@ -2892,6 +2898,7 @@ static void pci_register_types(void)
> >  {
> >      type_register_static(&pci_bus_info);
> >      type_register_static(&pcie_bus_info);
> > +    type_register_static(&cxl_bus_info);
> >      type_register_static(&conventional_pci_interface_info);
> >      type_register_static(&cxl_interface_info);
> >      type_register_static(&pcie_interface_info);
> > diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> > index 908896ebe8..97cbbad375 100644
> > --- a/include/hw/pci/pci.h
> > +++ b/include/hw/pci/pci.h
> > @@ -409,6 +409,7 @@ typedef PCIINTxRoute (*pci_route_irq_fn)(void *opaque, int pin);
> >  #define TYPE_PCI_BUS "PCI"
> >  OBJECT_DECLARE_TYPE(PCIBus, PCIBusClass, PCI_BUS)
> >  #define TYPE_PCIE_BUS "PCIE"
> > +#define TYPE_CXL_BUS "CXL"
> >  
> >  typedef void (*pci_bus_dev_fn)(PCIBus *b, PCIDevice *d, void *opaque);
> >  typedef void (*pci_bus_fn)(PCIBus *b, void *opaque);
> > @@ -768,6 +769,11 @@ static inline void pci_irq_pulse(PCIDevice *pci_dev)
> >      pci_irq_deassert(pci_dev);
> >  }
> >  
> > +static inline int pci_is_cxl(const PCIDevice *d)
> > +{
> > +    return d->cap_present & QEMU_PCIE_CAP_CXL;
> > +}
> > +
> >  static inline int pci_is_express(const PCIDevice *d)
> >  {
> >      return d->cap_present & QEMU_PCI_CAP_EXPRESS;  
> 
>