[RFC,qemu,5/6] hw/mem/cxl-type3: Add properties to control link speed and width

Commit Message

Jonathan Cameron July 12, 2024, 12:24 p.m. UTC

To establish performance characteristics of a CXL device when used via a
particular CXL topology (root ports, switches, end points) it is necessary
to set the appropriate link speed and width in the PCI Express capability
structure.  Provide x-speed and x-link properties for this.

Signed-off-by: Jonathan Cameron <[e-mail]>
---
 include/hw/cxl/cxl_device.h | 4 ++++
 hw/mem/cxl_type3.c          | 6 ++++++
 2 files changed, 10 insertions(+)

Patch

diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
index fdd0f4e62b..e14e56ae4b 100644
--- a/include/hw/cxl/cxl_device.h
+++ b/include/hw/cxl/cxl_device.h
@@ -549,6 +549,10 @@  struct CXLType3Dev {
     CXLCCI vdm_fm_owned_ld_mctp_cci;
     CXLCCI ld0_cci;
 
+    /* PCIe link characteristics */
+    PCIExpLinkSpeed speed;
+    PCIExpLinkWidth width;
+
     /* DOE */
     DOECap doe_cdat;
 
diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
index b3a401bc6d..adfcc28a6e 100644
--- a/hw/mem/cxl_type3.c
+++ b/hw/mem/cxl_type3.c
@@ -17,6 +17,7 @@ 
 #include "hw/mem/pc-dimm.h"
 #include "hw/pci/pci.h"
 #include "hw/qdev-properties.h"
+#include "hw/qdev-properties-system.h"
 #include "qapi/error.h"
 #include "qemu/log.h"
 #include "qemu/module.h"
@@ -1200,6 +1201,7 @@  static void ct3d_reset(DeviceState *dev)
     uint32_t *reg_state = ct3d->cxl_cstate.crb.cache_mem_registers;
     uint32_t *write_msk = ct3d->cxl_cstate.crb.cache_mem_regs_write_mask;
 
+    pcie_cap_fill_link_ep_usp(PCI_DEVICE(dev), ct3d->width, ct3d->speed);
     cxl_component_register_init_common(reg_state, write_msk, CXL2_TYPE3_DEVICE);
     cxl_device_register_init_t3(ct3d);
 
@@ -1229,6 +1231,10 @@  static Property ct3_props[] = {
     DEFINE_PROP_UINT8("num-dc-regions", CXLType3Dev, dc.num_regions, 0),
     DEFINE_PROP_LINK("volatile-dc-memdev", CXLType3Dev, dc.host_dc,
                      TYPE_MEMORY_BACKEND, HostMemoryBackend *),
+    DEFINE_PROP_PCIE_LINK_SPEED("x-speed", CXLType3Dev,
+                                speed, PCIE_LINK_SPEED_32),
+    DEFINE_PROP_PCIE_LINK_WIDTH("x-width", CXLType3Dev,
+                                width, PCIE_LINK_WIDTH_16),
     DEFINE_PROP_END_OF_LIST(),
 };