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0a867568bb
In Restricted CXL Device (RCD) mode a CXL device is exposed as an RCiEP, but CXL downstream and upstream ports are not enumerated and not visible in the PCIe hierarchy. [1] Protocol and link errors from these non-enumerated ports are signaled as internal AER errors, either Uncorrectable Internal Error (UIE) or Corrected Internal Errors (CIE) via an RCEC. Restricted CXL host (RCH) downstream port-detected errors have the Requester ID of the RCEC set in the RCEC's AER Error Source ID register. A CXL handler must then inspect the error status in various CXL registers residing in the dport's component register space (CXL RAS capability) or the dport's RCRB (PCIe AER extended capability). [2] Errors showing up in the RCEC's error handler must be handled and connected to the CXL subsystem. Implement this by forwarding the error to all CXL devices below the RCEC. Since the entire CXL device is controlled only using PCIe Configuration Space of device 0, function 0, only pass it there [3]. The error handling is limited to currently supported devices with the Memory Device class code set (CXL Type 3 Device, PCI_CLASS_MEMORY_CXL, 502h), handle downstream port errors in the device's cxl_pci driver. Support for other CXL Device Types (e.g. a CXL.cache Device) can be added later. To handle downstream port errors in addition to errors directed to the CXL endpoint device, a handler must also inspect the CXL RAS and PCIe AER capabilities of the CXL downstream port the device is connected to. Since CXL downstream port errors are signaled using internal errors, the handler requires those errors to be unmasked. This is subject of a follow-on patch. The reason for choosing this implementation is that the AER service driver claims the RCEC device, but does not allow it to register a custom specific handler to support CXL. Connecting the RCEC hard-wired with a CXL handler does not work, as the CXL subsystem might not be present all the time. The alternative to add an implementation to the portdrv to allow the registration of a custom RCEC error handler isn't worth doing it as CXL would be its only user. Instead, just check for an CXL RCEC and pass it down to the connected CXL device's error handler. With this approach the code can entirely be implemented in the PCIe AER driver and is independent of the CXL subsystem. The CXL driver only provides the handler. [1] CXL 3.0 spec: 9.11.8 CXL Devices Attached to an RCH [2] CXL 3.0 spec, 12.2.1.1 RCH Downstream Port-detected Errors [3] CXL 3.0 spec, 8.1.3 PCIe DVSEC for CXL Devices Co-developed-by: Terry Bowman <terry.bowman@amd.com> Signed-off-by: Terry Bowman <terry.bowman@amd.com> Signed-off-by: Robert Richter <rrichter@amd.com> Cc: Oliver O'Halloran <oohall@gmail.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-pci@vger.kernel.org Acked-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Reviewed-by: Dave Jiang <dave.jiang@intel.com> Link: https://lore.kernel.org/r/20231018171713.1883517-18-rrichter@amd.com Signed-off-by: Dan Williams <dan.j.williams@intel.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.