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[RFC PATCH v2 25/32] hw/cxl/device: Implement MMIO HDM decoding (8.2.5.1


From: Ben Widawsky
Subject: [RFC PATCH v2 25/32] hw/cxl/device: Implement MMIO HDM decoding (8.2.5.12)
Date: Tue, 5 Jan 2021 08:53:16 -0800

A device's volatile and persistent memory are known Host Defined Memory
(HDM) regions. The mechanism by which the device is programmed to claim
the addresses associated with those regions is through dedicated logic
known as the HDM decoder. In order to allow the OS to properly program
the HDMs, the HDM decoders must be modeled.

There are two ways the HDM decoders can be implemented, the legacy
mechanism is through the PCIe DVSEC programming from CXL 1.1 (8.1.3.8),
and MMIO is found in 8.2.5.12 of the spec. For now, 8.1.3.8 is not
implemented.

Much of CXL device logic is implemented in cxl-utils. The HDM decoder
however is implemented directly by the device implementation. The
generic cxl-utils probably should be the correct place to put this since
HDM decoders aren't unique to a type3 device. It is however easier at
the moment, and requires less design consideration to simply implement
it in the device, and figure out how to consolidate it later.

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
---
 hw/mem/cxl_type3.c | 82 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 77 insertions(+), 5 deletions(-)

diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
index 3985bb8d0b..dee5a8884b 100644
--- a/hw/mem/cxl_type3.c
+++ b/hw/mem/cxl_type3.c
@@ -57,6 +57,71 @@ static void build_dvsecs(CXLType3Dev *ct3d)
                                REG_LOC_DVSEC_REVID, dvsec);
 }
 
+static void hdm_decoder_commit(CXLType3Dev *ct3d, int which)
+{
+    MemoryRegion *pmem = ct3d->cxl_dstate.pmem;
+    MemoryRegion *mr = host_memory_backend_get_memory(ct3d->hostmem);
+    Range window, device;
+    ComponentRegisters *cregs = &ct3d->cxl_cstate.crb;
+    uint32_t *cache_mem = cregs->cache_mem_registers;
+    uint64_t offset, size;
+    Error *err = NULL;
+
+    assert(which == 0);
+
+    ARRAY_FIELD_DP32(cache_mem, CXL_HDM_DECODER0_CTRL, COMMIT, 0);
+    ARRAY_FIELD_DP32(cache_mem, CXL_HDM_DECODER0_CTRL, ERROR, 0);
+
+    offset = ((uint64_t)cache_mem[R_CXL_HDM_DECODER0_BASE_HI] << 32) |
+             cache_mem[R_CXL_HDM_DECODER0_BASE_LO];
+    size = ((uint64_t)cache_mem[R_CXL_HDM_DECODER0_SIZE_HI] << 32) |
+           cache_mem[R_CXL_HDM_DECODER0_SIZE_LO];
+
+    range_init_nofail(&window, mr->addr, memory_region_size(mr));
+    range_init_nofail(&device, offset, size);
+
+    if (!range_contains_range(&window, &device)) {
+        ARRAY_FIELD_DP32(cache_mem, CXL_HDM_DECODER0_CTRL, ERROR, 1);
+        return;
+    }
+
+    memory_region_ram_resize(pmem, size, &err);
+    if (err) {
+        ARRAY_FIELD_DP32(cache_mem, CXL_HDM_DECODER0_CTRL, ERROR, 1);
+        return;
+    }
+
+    offset -= mr->addr;
+    memory_region_add_subregion(mr, offset, pmem);
+
+    ARRAY_FIELD_DP32(cache_mem, CXL_HDM_DECODER0_CTRL, COMMITTED, 1);
+}
+
+static void ct3d_reg_write(void *opaque, hwaddr offset, uint64_t value, 
unsigned size)
+{
+    CXLComponentState *cxl_cstate = opaque;
+    ComponentRegisters *cregs = &cxl_cstate->crb;
+    CXLType3Dev *ct3d = container_of(cxl_cstate, CXLType3Dev, cxl_cstate);
+    uint32_t *cache_mem = cregs->cache_mem_registers;
+    bool should_commit = false;
+    int which_hdm = -1;
+
+    assert(size == 4);
+
+    switch (offset) {
+    case A_CXL_HDM_DECODER0_CTRL:
+        should_commit = FIELD_EX32(value, CXL_HDM_DECODER0_CTRL, COMMIT);
+        which_hdm = 0;
+        break;
+    default:
+        break;
+    }
+
+    stl_le_p((uint8_t *)cache_mem + offset, value);
+    if (should_commit)
+        hdm_decoder_commit(ct3d, which_hdm);
+}
+
 static void ct3_instance_init(Object *obj)
 {
     /* MemoryDeviceClass *mdc = MEMORY_DEVICE_GET_CLASS(obj); */
@@ -65,7 +130,10 @@ static void ct3_instance_init(Object *obj)
 static void ct3_finalize(Object *obj)
 {
     CXLType3Dev *ct3d = CT3(obj);
+    CXLComponentState *cxl_cstate = &ct3d->cxl_cstate;
+    ComponentRegisters *regs = &cxl_cstate->crb;
 
+    g_free((void *)regs->special_ops);
     g_free(ct3d->cxl_dstate.pmem);
 }
 
@@ -81,11 +149,12 @@ static void cxl_setup_memory(CXLType3Dev *ct3d, Error 
**errp)
         return;
     }
 
-    /* FIXME: need to check mr is the host bridge's MR */
-    mr = host_memory_backend_get_memory(ct3d->hostmem);
-
     /* Create our new subregion */
     ct3d->cxl_dstate.pmem = g_new(MemoryRegion, 1);
+    memory_region_set_nonvolatile(ct3d->cxl_dstate.pmem, true);
+
+    /* FIXME: need to check mr is the host bridge's MR */
+    mr = host_memory_backend_get_memory(ct3d->hostmem);
 
     /* Find the first free space in the window */
     WITH_RCU_READ_LOCK_GUARD()
@@ -108,8 +177,6 @@ static void cxl_setup_memory(CXLType3Dev *ct3d, Error 
**errp)
     /* Register our subregion as non-volatile */
     memory_region_init_ram(ct3d->cxl_dstate.pmem, OBJECT(ct3d),
                            "cxl_type3-memory", ct3d->size, errp);
-    memory_region_set_nonvolatile(ct3d->cxl_dstate.pmem, true);
-
 #ifdef SET_PMEM_PADDR
     memory_region_add_subregion(mr, offset, ct3d->cxl_dstate.pmem);
 #endif
@@ -148,6 +215,11 @@ static void ct3_realize(PCIDevice *pci_dev, Error **errp)
     ct3d->cxl_cstate.pdev = pci_dev;
     build_dvsecs(ct3d);
 
+#ifndef SET_PMEM_PADDR
+    regs->special_ops = g_new0(MemoryRegionOps, 1);
+    regs->special_ops->write = ct3d_reg_write;
+#endif
+
     cxl_component_register_block_init(OBJECT(pci_dev), cxl_cstate,
                                       TYPE_CXL_TYPE3_DEV);
 
-- 
2.30.0




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