mem/cxl_type3: Add read and write functions for associated hostmem.

Once a read or write reaches a CXL type 3 device, the HDM decoders
on the device are used to establish the Device Physical Address
which should be accessed.  These functions peform the required maths
and then use a device specific address space to access the
hostmem->mr to fullfil the actual operation.  Note that failed writes
are silent, but failed reads return poison.  Note this is based
loosely on:

https://lore.kernel.org/qemu-devel/20200817161853.593247-6-f4bug@amsat.org/
[RFC PATCH 0/9] hw/misc: Add support for interleaved memory accesses

Only lightly tested so far.  More complex test cases yet to be written.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20220429144110.25167-33-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/mem/cxl_type3.c

@@ -97,7 +97,9 @@ static void ct3d_reg_write(void *opaque, hwaddr offset, uint64_t value,
 
 static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
 {
+    DeviceState *ds = DEVICE(ct3d);
     MemoryRegion *mr;
+    char *name;
 
     if (!ct3d->hostmem) {
         error_setg(errp, "memdev property must be set");
@@ -112,6 +114,15 @@ static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
     memory_region_set_nonvolatile(mr, true);
     memory_region_set_enabled(mr, true);
     host_memory_backend_set_mapped(ct3d->hostmem, true);
+
+    if (ds->id) {
+        name = g_strdup_printf("cxl-type3-dpa-space:%s", ds->id);
+    } else {
+        name = g_strdup("cxl-type3-dpa-space");
+    }
+    address_space_init(&ct3d->hostmem_as, mr, name);
+    g_free(name);
+
     ct3d->cxl_dstate.pmem_size = ct3d->hostmem->size;
 
     if (!ct3d->lsa) {
@@ -167,6 +178,86 @@ static void ct3_exit(PCIDevice *pci_dev)
     ComponentRegisters *regs = &cxl_cstate->crb;
 
     g_free(regs->special_ops);
+    address_space_destroy(&ct3d->hostmem_as);
+}
+
+/* TODO: Support multiple HDM decoders and DPA skip */
+static bool cxl_type3_dpa(CXLType3Dev *ct3d, hwaddr host_addr, uint64_t *dpa)
+{
+    uint32_t *cache_mem = ct3d->cxl_cstate.crb.cache_mem_registers;
+    uint64_t decoder_base, decoder_size, hpa_offset;
+    uint32_t hdm0_ctrl;
+    int ig, iw;
+
+    decoder_base = (((uint64_t)cache_mem[R_CXL_HDM_DECODER0_BASE_HI] << 32) |
+                    cache_mem[R_CXL_HDM_DECODER0_BASE_LO]);
+    if ((uint64_t)host_addr < decoder_base) {
+        return false;
+    }
+
+    hpa_offset = (uint64_t)host_addr - decoder_base;
+
+    decoder_size = ((uint64_t)cache_mem[R_CXL_HDM_DECODER0_SIZE_HI] << 32) |
+        cache_mem[R_CXL_HDM_DECODER0_SIZE_LO];
+    if (hpa_offset >= decoder_size) {
+        return false;
+    }
+
+    hdm0_ctrl = cache_mem[R_CXL_HDM_DECODER0_CTRL];
+    iw = FIELD_EX32(hdm0_ctrl, CXL_HDM_DECODER0_CTRL, IW);
+    ig = FIELD_EX32(hdm0_ctrl, CXL_HDM_DECODER0_CTRL, IG);
+
+    *dpa = (MAKE_64BIT_MASK(0, 8 + ig) & hpa_offset) |
+        ((MAKE_64BIT_MASK(8 + ig + iw, 64 - 8 - ig - iw) & hpa_offset) >> iw);
+
+    return true;
+}
+
+MemTxResult cxl_type3_read(PCIDevice *d, hwaddr host_addr, uint64_t *data,
+                           unsigned size, MemTxAttrs attrs)
+{
+    CXLType3Dev *ct3d = CXL_TYPE3(d);
+    uint64_t dpa_offset;
+    MemoryRegion *mr;
+
+    /* TODO support volatile region */
+    mr = host_memory_backend_get_memory(ct3d->hostmem);
+    if (!mr) {
+        return MEMTX_ERROR;
+    }
+
+    if (!cxl_type3_dpa(ct3d, host_addr, &dpa_offset)) {
+        return MEMTX_ERROR;
+    }
+
+    if (dpa_offset > int128_get64(mr->size)) {
+        return MEMTX_ERROR;
+    }
+
+    return address_space_read(&ct3d->hostmem_as, dpa_offset, attrs, data, size);
+}
+
+MemTxResult cxl_type3_write(PCIDevice *d, hwaddr host_addr, uint64_t data,
+                            unsigned size, MemTxAttrs attrs)
+{
+    CXLType3Dev *ct3d = CXL_TYPE3(d);
+    uint64_t dpa_offset;
+    MemoryRegion *mr;
+
+    mr = host_memory_backend_get_memory(ct3d->hostmem);
+    if (!mr) {
+        return MEMTX_OK;
+    }
+
+    if (!cxl_type3_dpa(ct3d, host_addr, &dpa_offset)) {
+        return MEMTX_OK;
+    }
+
+    if (dpa_offset > int128_get64(mr->size)) {
+        return MEMTX_OK;
+    }
+    return address_space_write(&ct3d->hostmem_as, dpa_offset, attrs,
+                               &data, size);
 }
 
 static void ct3d_reset(DeviceState *dev)

include/hw/cxl/cxl_device.h

@@ -239,6 +239,7 @@ struct CXLType3Dev {
     HostMemoryBackend *lsa;
 
     /* State */
+    AddressSpace hostmem_as;
     CXLComponentState cxl_cstate;
     CXLDeviceState cxl_dstate;
 };
@@ -259,4 +260,9 @@ struct CXLType3Class {
                     uint64_t offset);
 };
 
+MemTxResult cxl_type3_read(PCIDevice *d, hwaddr host_addr, uint64_t *data,
+                           unsigned size, MemTxAttrs attrs);
+MemTxResult cxl_type3_write(PCIDevice *d, hwaddr host_addr, uint64_t data,
+                            unsigned size, MemTxAttrs attrs);
+
 #endif