[PATCH v4 34/42] mem/cxl_type3: Add read and write functions for associated hostmem.

[Jonathan Cameron via <qemu-devel@nongnu.org>]

From: Jonathan Cameron <jonathan.cameron@huawei.com>

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 directly 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>
---
 hw/mem/cxl_type3.c          | 81 +++++++++++++++++++++++++++++++++++++
 include/hw/cxl/cxl_device.h |  5 +++
 2 files changed, 86 insertions(+)

diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
index e99d84c92d..eb0203dcbc 100644
--- a/hw/mem/cxl_type3.c
+++ b/hw/mem/cxl_type3.c
@@ -161,6 +161,87 @@ static void ct3_realize(PCIDevice *pci_dev, Error **errp)
                      &ct3d->cxl_dstate.device_registers);
 }
 
+/* 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 = CT3(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 > mr->size) {
+        return MEMTX_ERROR;
+    }
+
+    return memory_region_dispatch_read(mr, dpa_offset, data,
+                                       size_memop(size), attrs);
+}
+
+MemTxResult cxl_type3_write(PCIDevice *d, hwaddr host_addr, uint64_t data,
+                            unsigned size, MemTxAttrs attrs)
+{
+    CXLType3Dev *ct3d = CT3(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 > mr->size) {
+        return MEMTX_OK;
+    }
+
+    return memory_region_dispatch_write(mr, dpa_offset, data,
+                                        size_memop(size), attrs);
+}
+
 static void ct3d_reset(DeviceState *dev)
 {
     CXLType3Dev *ct3d = CT3(dev);
diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
index 0426714e9b..0f6adbae32 100644
--- a/include/hw/cxl/cxl_device.h
+++ b/include/hw/cxl/cxl_device.h
@@ -258,4 +258,9 @@ 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
-- 
2.32.0