Re: [PATCH qemu] hw/pci-bridge/pxb-cxl: Drop RAS capability from host bridge.

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

On Thu, 15 Feb 2024 11:11:47 -0500
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Thu, Feb 15, 2024 at 03:52:06PM +0000, Jonathan Cameron wrote:
> > This CXL component isn't allowed to have a RAS capability.
> > Whilst this should be harmless as software is not expected to look
> > here, good to clean it up.
> > 
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>  
> 
> Isn't this device migrateable? If yes you need compat
> handling.

Not yet. Migrating these is broken in lots of ways :(

Given they are functional emulation only I've never cared that much.
We'll need to fix this as part of adding support for virtualization
use cases which start to make sense when dynamic capacity
support lands in kernel + QEMU (probably later this year)

Jonathan

> 
> 
> > ---
> >  I've been carrying this on my tree for quite a while.
> >  This wasn't in previous fixes set because it's low priority and
> >  rebasing it across cleanup series that followed those fixes was
> >  too fiddly to bother.
> >  
> >  include/hw/cxl/cxl_component.h      |  1 +
> >  hw/cxl/cxl-component-utils.c        | 21 +++++++++++++++++----
> >  hw/pci-bridge/pci_expander_bridge.c |  2 +-
> >  3 files changed, 19 insertions(+), 5 deletions(-)
> > 
> > diff --git a/include/hw/cxl/cxl_component.h b/include/hw/cxl/cxl_component.h
> > index 0e5d35c263..5012fab6f7 100644
> > --- a/include/hw/cxl/cxl_component.h
> > +++ b/include/hw/cxl/cxl_component.h
> > @@ -25,6 +25,7 @@ enum reg_type {
> >      CXL2_TYPE3_DEVICE,
> >      CXL2_LOGICAL_DEVICE,
> >      CXL2_ROOT_PORT,
> > +    CXL2_RC,
> >      CXL2_UPSTREAM_PORT,
> >      CXL2_DOWNSTREAM_PORT,
> >      CXL3_SWITCH_MAILBOX_CCI,
> > diff --git a/hw/cxl/cxl-component-utils.c b/hw/cxl/cxl-component-utils.c
> > index 84ab503325..cd116c0401 100644
> > --- a/hw/cxl/cxl-component-utils.c
> > +++ b/hw/cxl/cxl-component-utils.c
> > @@ -297,6 +297,7 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> >          caps = 3;
> >          break;
> >      case CXL2_ROOT_PORT:
> > +    case CXL2_RC:
> >          /* + Extended Security, + Snoop */
> >          caps = 5;
> >          break;
> > @@ -326,8 +327,19 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> >                         CXL_##reg##_REGISTERS_OFFSET);                         \
> >      } while (0)
> >  
> > +    switch (type) {
> > +    case CXL2_DEVICE:
> > +    case CXL2_TYPE3_DEVICE:
> > +    case CXL2_LOGICAL_DEVICE:
> > +    case CXL2_ROOT_PORT:
> > +    case CXL2_UPSTREAM_PORT:
> > +    case CXL2_DOWNSTREAM_PORT:
> >      init_cap_reg(RAS, 2, CXL_RAS_CAPABILITY_VERSION);
> > -    ras_init_common(reg_state, write_msk);
> > +        ras_init_common(reg_state, write_msk);
> > +        break;
> > +    default:
> > +        break;
> > +    }
> >  
> >      init_cap_reg(LINK, 4, CXL_LINK_CAPABILITY_VERSION);
> >  
> > @@ -335,9 +347,10 @@ void cxl_component_register_init_common(uint32_t *reg_state,
> >          return;
> >      }
> >  
> > -    init_cap_reg(HDM, 5, CXL_HDM_CAPABILITY_VERSION);
> > -    hdm_init_common(reg_state, write_msk, type);
> > -
> > +    if (type != CXL2_ROOT_PORT) {
> > +        init_cap_reg(HDM, 5, CXL_HDM_CAPABILITY_VERSION);
> > +        hdm_init_common(reg_state, write_msk, type);
> > +    }
> >      if (caps < 5) {
> >          return;
> >      }
> > diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> > index 535889f7c2..0411ad31ea 100644
> > --- a/hw/pci-bridge/pci_expander_bridge.c
> > +++ b/hw/pci-bridge/pci_expander_bridge.c
> > @@ -290,7 +290,7 @@ static void pxb_cxl_dev_reset(DeviceState *dev)
> >      uint32_t *write_msk = cxl_cstate->crb.cache_mem_regs_write_mask;
> >      int dsp_count = 0;
> >  
> > -    cxl_component_register_init_common(reg_state, write_msk, CXL2_ROOT_PORT);
> > +    cxl_component_register_init_common(reg_state, write_msk, CXL2_RC);
> >      /*
> >       * The CXL specification allows for host bridges with no HDM decoders
> >       * if they only have a single root port.
> > -- 
> > 2.39.2  
>