Re: [PATCH v2] hw/cxl/device: Add Flex Bus Port DVSEC

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Dec 16, 2022 at 09:31:36AM +0000, Jonathan Cameron wrote:
> On Thu, 15 Dec 2022 09:28:30 -0800
> Ira Weiny <ira.weiny@intel.com> wrote:
> 
> > On Thu, Dec 15, 2022 at 05:16:33PM +0000, Jonathan Cameron wrote:
> > > On Wed, 14 Dec 2022 12:54:11 -0800
> > > Ira Weiny <ira.weiny@intel.com> wrote:
> > >   
> > > > The Flex Bus Port DVSEC was missing on type 3 devices which was blocking
> > > > RAS checks.[1]
> > > > 
> > > > Add the Flex Bus Port DVSEC to type 3 devices as per CXL 3.0 8.2.1.3.
> > > > 
> > > > [1] https://lore.kernel.org/linux-cxl/167096738875.2861540.11815053323626849940.stgit@djiang5-desk3.ch.intel.com/
> > > > 
> > > > Cc: Dave Jiang <dave.jiang@intel.com>
> > > > Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > > Cc: Ben Widawsky <bwidawsk@kernel.org>
> > > > Cc: qemu-devel@nongnu.org
> > > > Cc: linux-cxl@vger.kernel.org
> > > > Signed-off-by: Ira Weiny <ira.weiny@intel.com>  
> > > Looks good to me.
> > > 
> > > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > > 
> > > As Michael wasn't cc'd on patch posting, so might not get this directly I'll add
> > > it to the front of the series adding the RAS event emulation on basis that's the
> > > first time we'll see a failure in Linux (I think?)  
> > 
> > Ah thanks!
> > 
> > Sorry, I thought you were the 'maintainer' of the CXL stuff for qemu.
> 
> Ah I am, but so far the CXL stuff has routed through Michael as PCI maintainer
> because of the high level of overlap. So far I've done that by grouping up
> patches and send them in sets to Michael. This one is more of a fix, so maybe
> wants to move quicker than I will.
> 
> This gives me a good opportunity to ask Michael:
> 
> How do you want us to handle this in future? I'd expect the overlap with the PCI
> core stuff to reduce going forwards, as most of the infrastructure is now in
> place and obviously would want you to look at anything that does touch core PCI
> code, but for the rest of it, would you prefer that I send pull requests going
> forwards?  I'm more than happy to keep dumping this stuff on you, but seems
> rather mean!
> 
> If we do move to pull requests, what scope of stuff do you want us to seek your
> review on?  If things go according to plan there will be a bunch of stuff related
> to the switch ports in the near future, some of which is going to add complex
> PCI topologies and new forms of hotplug so I'll definitely want your input on
> that, but we also have a bunch of stuff around memory error reporting etc which
> I'm thinking may be of less interest to you. Obviously I'd love it if you have
> time to review everything but don't want to impose unnecessarily.
> 
> Jonathan

It's not been too bad so far :) I'm not used to reviewing pull requests
- patches are easier if you want my review. If you are happy too then
all is well. Yes I assume if I'm CC'd directly people want my input
if not then not. And learning a bit about how error reporting works
is interesting to me.

But if you want to send some pulls directly that's fine too, at this point
I trust you to do the right thing.


> 
> > 
> > > 
> > > Michael, if you want to pick this up directly that's great too!  
> > 
> > Should I send directly to Michael in future?
> > 
> > > 
> > > As a side note the WTF? is because we made up a hardware related time delay
> > > number having no idea whatsoever on what a realistic value was. Cut and paste
> > > from the instances of this structure in the root port and the switch ports.
> > >   
> > 
> > Yep I just followed that based off the other code.
> > 
> > Ira
> > 
> > > Jonathan
> > > 
> > > 
> > >   
> > > > ---
> > > > Changes in v2:
> > > >         Jonathan                                                            
> > > >                 type 3 device does not support CACHE                        
> > > >                 Comment the 68B bit                                         
> > > > 
> > > > - Link to v1: https://lore.kernel.org/r/20221213-ira-flexbus-port-v1-1-86afd4f30be6@intel.com
> > > > ---
> > > >  hw/mem/cxl_type3.c | 11 +++++++++++
> > > >  1 file changed, 11 insertions(+)
> > > > 
> > > > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > > > index 0317bd96a6fb..e6beac143fc1 100644
> > > > --- a/hw/mem/cxl_type3.c
> > > > +++ b/hw/mem/cxl_type3.c
> > > > @@ -416,6 +416,17 @@ static void build_dvsecs(CXLType3Dev *ct3d)
> > > >      cxl_component_create_dvsec(cxl_cstate, CXL2_TYPE3_DEVICE,
> > > >                                 GPF_DEVICE_DVSEC_LENGTH, GPF_DEVICE_DVSEC,
> > > >                                 GPF_DEVICE_DVSEC_REVID, dvsec);
> > > > +
> > > > +    dvsec = (uint8_t *)&(CXLDVSECPortFlexBus){
> > > > +        .cap                     = 0x26, /* 68B, IO, Mem, non-MLD */
> > > > +        .ctrl                    = 0x02, /* IO always enabled */
> > > > +        .status                  = 0x26, /* same as capabilities */
> > > > +        .rcvd_mod_ts_data_phase1 = 0xef, /* WTF? */
> > > > +    };
> > > > +    cxl_component_create_dvsec(cxl_cstate, CXL2_TYPE3_DEVICE,
> > > > +                               PCIE_FLEXBUS_PORT_DVSEC_LENGTH_2_0,
> > > > +                               PCIE_FLEXBUS_PORT_DVSEC,
> > > > +                               PCIE_FLEXBUS_PORT_DVSEC_REVID_2_0, dvsec);
> > > >  }
> > > >  
> > > >  static void hdm_decoder_commit(CXLType3Dev *ct3d, int which)
> > > > 
> > > > ---
> > > > base-commit: e11b57108b0cb746bb9f3887054f34a2f818ed79
> > > > change-id: 20221213-ira-flexbus-port-ce526de8111d
> > > > 
> > > > Best regards,  
> > >