[v7,06/12] hw/mem/cxl_type3: Add host backend and address space handling for DC regions

Commit Message

Fan Ni April 18, 2024, 11:10 p.m. UTC

From: Fan Ni <[e-mail]>

Add (file/memory backed) host backend for DCD. All the dynamic capacity
regions will share a single, large enough host backend. Set up address
space for DC regions to support read/write operations to dynamic capacity
for DCD.

With the change, the following support is added:
1. Add a new property to type3 device "volatile-dc-memdev" to point to host
   memory backend for dynamic capacity. Currently, all DC regions share one
   host backend;
2. Add namespace for dynamic capacity for read/write support;
3. Create cdat entries for each dynamic capacity region.

Signed-off-by: Fan Ni <[e-mail]>
---
 hw/cxl/cxl-mailbox-utils.c  |  16 ++--
 hw/mem/cxl_type3.c          | 172 +++++++++++++++++++++++++++++-------
 include/hw/cxl/cxl_device.h |   8 ++
 3 files changed, 160 insertions(+), 36 deletions(-)

Comments

Gregory Price April 19, 2024, 5:27 p.m. UTC | #1

On Thu, Apr 18, 2024 at 04:10:57PM -0700, [e-mail] wrote:
> From: Fan Ni <[e-mail]>
> 
> Add (file/memory backed) host backend for DCD. All the dynamic capacity
> regions will share a single, large enough host backend. Set up address
> space for DC regions to support read/write operations to dynamic capacity
> for DCD.
> 
> With the change, the following support is added:
> 1. Add a new property to type3 device "volatile-dc-memdev" to point to host
>    memory backend for dynamic capacity. Currently, all DC regions share one
>    host backend;
> 2. Add namespace for dynamic capacity for read/write support;
> 3. Create cdat entries for each dynamic capacity region.
> 
> Signed-off-by: Fan Ni <[e-mail]>
> ---
>  hw/cxl/cxl-mailbox-utils.c  |  16 ++--
>  hw/mem/cxl_type3.c          | 172 +++++++++++++++++++++++++++++-------
>  include/hw/cxl/cxl_device.h |   8 ++
>  3 files changed, 160 insertions(+), 36 deletions(-)
> 

A couple general comments in line for discussion, but patch looks good
otherwise. Notes are mostly on improvements we could make that should
not block this patch.

Reviewed-by: Gregory Price <[e-mail]>

>  
> diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> index a1fe268560..ac87398089 100644
> --- a/hw/mem/cxl_type3.c
> +++ b/hw/mem/cxl_type3.c
> @@ -45,7 +45,8 @@ enum {
>  
>  static void ct3_build_cdat_entries_for_mr(CDATSubHeader **cdat_table,
>                                            int dsmad_handle, uint64_t size,
> -                                          bool is_pmem, uint64_t dpa_base)
> +                                          bool is_pmem, bool is_dynamic,
> +                                          uint64_t dpa_base)

We should probably change the is_* fields into a flags field and do some
error checking on the combination of flags.

>  {
>      CDATDsmas *dsmas;
>      CDATDslbis *dslbis0;
> @@ -61,7 +62,8 @@ static void ct3_build_cdat_entries_for_mr(CDATSubHeader **cdat_table,
>              .length = sizeof(*dsmas),
>          },
>          .DSMADhandle = dsmad_handle,
> -        .flags = is_pmem ? CDAT_DSMAS_FLAG_NV : 0,
> +        .flags = (is_pmem ? CDAT_DSMAS_FLAG_NV : 0) |
> +                 (is_dynamic ? CDAT_DSMAS_FLAG_DYNAMIC_CAP : 0),

For example, as noted elsewhere in the code, is_pmem+is_dynamic is not
presently supported, so this shouldn't even be allowed in this function.

> +    if (dc_mr) {
> +        int i;
> +        uint64_t region_base = vmr_size + pmr_size;
> +
> +        /*
> +         * TODO: we assume the dynamic capacity to be volatile for now.
> +         * Non-volatile dynamic capacity will be added if needed in the
> +         * future.
> +         */

Probably don't need to mark this TODO, can just leave it as a note.

Non-volatile dynamic capacity will coincide with shared memory, so it'll
end up handled.  So this isn't really a TODO for this current work, and
should read more like:

"Dynamic Capacity is always volatile, until shared memory is
implemented"

> +    } else if (ct3d->hostpmem) {
>          range1_size_hi = ct3d->hostpmem->size >> 32;
>          range1_size_lo = (2 << 5) | (2 << 2) | 0x3 |
>                           (ct3d->hostpmem->size & 0xF0000000);
> +    } else {
> +        /*
> +         * For DCD with no static memory, set memory active, memory class bits.
> +         * No range is set.
> +         */
> +        range1_size_lo = (2 << 5) | (2 << 2) | 0x3;

We should probably add defs for these fields at some point. Can be
tabled for later work though.

> +        /*
> +         * TODO: set dc as volatile for now, non-volatile support can be added
> +         * in the future if needed.
> +         */
> +        memory_region_set_nonvolatile(dc_mr, false);

Again can probably drop the TODO and just leave a statement.

~Gregory

Jonathan Cameron April 22, 2024, 11:52 a.m. UTC | #2

On Thu, 18 Apr 2024 16:10:57 -0700
[e-mail] wrote:

> From: Fan Ni <[e-mail]>
> 
> Add (file/memory backed) host backend for DCD. All the dynamic capacity
> regions will share a single, large enough host backend. Set up address
> space for DC regions to support read/write operations to dynamic capacity
> for DCD.
> 
> With the change, the following support is added:
> 1. Add a new property to type3 device "volatile-dc-memdev" to point to host
>    memory backend for dynamic capacity. Currently, all DC regions share one
>    host backend;
> 2. Add namespace for dynamic capacity for read/write support;
> 3. Create cdat entries for each dynamic capacity region.
> 
> Signed-off-by: Fan Ni <[e-mail]>
One fixlet needed inline.

I've set range1_size_lo = 0 there for my tree.

> @@ -301,10 +337,16 @@ static void build_dvsecs(CXLType3Dev *ct3d)
>              range2_size_lo = (2 << 5) | (2 << 2) | 0x3 |
>                               (ct3d->hostpmem->size & 0xF0000000);
>          }
> -    } else {
> +    } else if (ct3d->hostpmem) {
>          range1_size_hi = ct3d->hostpmem->size >> 32;
>          range1_size_lo = (2 << 5) | (2 << 2) | 0x3 |
>                           (ct3d->hostpmem->size & 0xF0000000);
> +    } else {
> +        /*
> +         * For DCD with no static memory, set memory active, memory class bits.
> +         * No range is set.
> +         */

range1_size_hi is not initialized.

> +        range1_size_lo = (2 << 5) | (2 << 2) | 0x3;
>      }
>  
>      dvsec = (uint8_t *)&(CXLDVSECDevice){

Jonathan Cameron April 22, 2024, 11:55 a.m. UTC | #3

On Fri, 19 Apr 2024 13:27:59 -0400
Gregory Price <[e-mail]> wrote:

> On Thu, Apr 18, 2024 at 04:10:57PM -0700, [e-mail] wrote:
> > From: Fan Ni <[e-mail]>
> > 
> > Add (file/memory backed) host backend for DCD. All the dynamic capacity
> > regions will share a single, large enough host backend. Set up address
> > space for DC regions to support read/write operations to dynamic capacity
> > for DCD.
> > 
> > With the change, the following support is added:
> > 1. Add a new property to type3 device "volatile-dc-memdev" to point to host
> >    memory backend for dynamic capacity. Currently, all DC regions share one
> >    host backend;
> > 2. Add namespace for dynamic capacity for read/write support;
> > 3. Create cdat entries for each dynamic capacity region.
> > 
> > Signed-off-by: Fan Ni <[e-mail]>
> > ---
> >  hw/cxl/cxl-mailbox-utils.c  |  16 ++--
> >  hw/mem/cxl_type3.c          | 172 +++++++++++++++++++++++++++++-------
> >  include/hw/cxl/cxl_device.h |   8 ++
> >  3 files changed, 160 insertions(+), 36 deletions(-)
> >   
> 
> A couple general comments in line for discussion, but patch looks good
> otherwise. Notes are mostly on improvements we could make that should
> not block this patch.
> 
> Reviewed-by: Gregory Price <[e-mail]>
> 
> >  
> > diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
> > index a1fe268560..ac87398089 100644
> > --- a/hw/mem/cxl_type3.c
> > +++ b/hw/mem/cxl_type3.c
> > @@ -45,7 +45,8 @@ enum {
> >  
> >  static void ct3_build_cdat_entries_for_mr(CDATSubHeader **cdat_table,
> >                                            int dsmad_handle, uint64_t size,
> > -                                          bool is_pmem, uint64_t dpa_base)
> > +                                          bool is_pmem, bool is_dynamic,
> > +                                          uint64_t dpa_base)  
> 
> We should probably change the is_* fields into a flags field and do some
> error checking on the combination of flags.
> 
> >  {
> >      CDATDsmas *dsmas;
> >      CDATDslbis *dslbis0;
> > @@ -61,7 +62,8 @@ static void ct3_build_cdat_entries_for_mr(CDATSubHeader **cdat_table,
> >              .length = sizeof(*dsmas),
> >          },
> >          .DSMADhandle = dsmad_handle,
> > -        .flags = is_pmem ? CDAT_DSMAS_FLAG_NV : 0,
> > +        .flags = (is_pmem ? CDAT_DSMAS_FLAG_NV : 0) |
> > +                 (is_dynamic ? CDAT_DSMAS_FLAG_DYNAMIC_CAP : 0),  
> 
> For example, as noted elsewhere in the code, is_pmem+is_dynamic is not
> presently supported, so this shouldn't even be allowed in this function.
> 
> > +    if (dc_mr) {
> > +        int i;
> > +        uint64_t region_base = vmr_size + pmr_size;
> > +
> > +        /*
> > +         * TODO: we assume the dynamic capacity to be volatile for now.
> > +         * Non-volatile dynamic capacity will be added if needed in the
> > +         * future.
> > +         */  
> 
> Probably don't need to mark this TODO, can just leave it as a note.
> 
> Non-volatile dynamic capacity will coincide with shared memory, so it'll
> end up handled.  So this isn't really a TODO for this current work, and
> should read more like:
> 
> "Dynamic Capacity is always volatile, until shared memory is
> implemented"

I can sort of see your logic, but there is a difference between
volatile memory that is shared and persistent memory (typically whether
we need to care about deep flushes in some architectures) so I'd expected
volatile shared capacity to still be a thing, even if the host OS treats
it in most ways as persistent.

Also, persistent + DCD could be a thing without sharing sometime in the
future.

> 
> > +    } else if (ct3d->hostpmem) {
> >          range1_size_hi = ct3d->hostpmem->size >> 32;
> >          range1_size_lo = (2 << 5) | (2 << 2) | 0x3 |
> >                           (ct3d->hostpmem->size & 0xF0000000);
> > +    } else {
> > +        /*
> > +         * For DCD with no static memory, set memory active, memory class bits.
> > +         * No range is set.
> > +         */
> > +        range1_size_lo = (2 << 5) | (2 << 2) | 0x3;  
> 
> We should probably add defs for these fields at some point. Can be
> tabled for later work though.
Agreed - worth tidying up but not on critical path.

> 
> > +        /*
> > +         * TODO: set dc as volatile for now, non-volatile support can be added
> > +         * in the future if needed.
> > +         */
> > +        memory_region_set_nonvolatile(dc_mr, false);  
> 
> Again can probably drop the TODO and just leave a statement.
> 
> ~Gregory

Zhijian Li (Fujitsu)" via May 14, 2024, 8:28 a.m. UTC | #4

On 19/04/2024 07:10, [e-mail] wrote:
> +    uint64_t dc_size;
> +
> +    mr = host_memory_backend_get_memory(ct3d->dc.host_dc);
> +    dc_size = memory_region_size(mr);
> +    region_len = DIV_ROUND_UP(dc_size, ct3d->dc.num_regions);
> +
> +    if (dc_size % (ct3d->dc.num_regions * CXL_CAPACITY_MULTIPLIER) != 0) {
> +        error_setg(errp, "host backend size must be multiples of region len");

I prefer to have the %region_len% in the error message as well so that i can update the
backend file accordingly.



> +        return false;
> +    }

Fan Ni May 16, 2024, 5:07 p.m. UTC | #5

On Tue, May 14, 2024 at 08:28:27AM +0000, Zhijian Li (Fujitsu) wrote:
> 
> 
> On 19/04/2024 07:10, [e-mail] wrote:
> > +    uint64_t dc_size;
> > +
> > +    mr = host_memory_backend_get_memory(ct3d->dc.host_dc);
> > +    dc_size = memory_region_size(mr);
> > +    region_len = DIV_ROUND_UP(dc_size, ct3d->dc.num_regions);
> > +
> > +    if (dc_size % (ct3d->dc.num_regions * CXL_CAPACITY_MULTIPLIER) != 0) {
> > +        error_setg(errp, "host backend size must be multiples of region len");
> 
> I prefer to have the %region_len% in the error message as well so that i can update the
> backend file accordingly.

Will add.

Fan
> 
> 
> 
> > +        return false;
> > +    }

Patch

diff --git a/hw/cxl/cxl-mailbox-utils.c b/hw/cxl/cxl-mailbox-utils.c
index 0f2ad58a14..831cef0567 100644
--- a/hw/cxl/cxl-mailbox-utils.c
+++ b/hw/cxl/cxl-mailbox-utils.c
@@ -622,7 +622,8 @@  static CXLRetCode cmd_firmware_update_get_info(const struct cxl_cmd *cmd,
                                                size_t *len_out,
                                                CXLCCI *cci)
 {
-    CXLDeviceState *cxl_dstate = &CXL_TYPE3(cci->d)->cxl_dstate;
+    CXLType3Dev *ct3d = CXL_TYPE3(cci->d);
+    CXLDeviceState *cxl_dstate = &ct3d->cxl_dstate;
     struct {
         uint8_t slots_supported;
         uint8_t slot_info;
@@ -636,7 +637,8 @@  static CXLRetCode cmd_firmware_update_get_info(const struct cxl_cmd *cmd,
     QEMU_BUILD_BUG_ON(sizeof(*fw_info) != 0x50);
 
     if ((cxl_dstate->vmem_size < CXL_CAPACITY_MULTIPLIER) ||
-        (cxl_dstate->pmem_size < CXL_CAPACITY_MULTIPLIER)) {
+        (cxl_dstate->pmem_size < CXL_CAPACITY_MULTIPLIER) ||
+        (ct3d->dc.total_capacity < CXL_CAPACITY_MULTIPLIER)) {
         return CXL_MBOX_INTERNAL_ERROR;
     }
 
@@ -793,7 +795,8 @@  static CXLRetCode cmd_identify_memory_device(const struct cxl_cmd *cmd,
     CXLDeviceState *cxl_dstate = &ct3d->cxl_dstate;
 
     if ((!QEMU_IS_ALIGNED(cxl_dstate->vmem_size, CXL_CAPACITY_MULTIPLIER)) ||
-        (!QEMU_IS_ALIGNED(cxl_dstate->pmem_size, CXL_CAPACITY_MULTIPLIER))) {
+        (!QEMU_IS_ALIGNED(cxl_dstate->pmem_size, CXL_CAPACITY_MULTIPLIER)) ||
+        (!QEMU_IS_ALIGNED(ct3d->dc.total_capacity, CXL_CAPACITY_MULTIPLIER))) {
         return CXL_MBOX_INTERNAL_ERROR;
     }
 
@@ -835,9 +838,11 @@  static CXLRetCode cmd_ccls_get_partition_info(const struct cxl_cmd *cmd,
         uint64_t next_pmem;
     } QEMU_PACKED *part_info = (void *)payload_out;
     QEMU_BUILD_BUG_ON(sizeof(*part_info) != 0x20);
+    CXLType3Dev *ct3d = container_of(cxl_dstate, CXLType3Dev, cxl_dstate);
 
     if ((!QEMU_IS_ALIGNED(cxl_dstate->vmem_size, CXL_CAPACITY_MULTIPLIER)) ||
-        (!QEMU_IS_ALIGNED(cxl_dstate->pmem_size, CXL_CAPACITY_MULTIPLIER))) {
+        (!QEMU_IS_ALIGNED(cxl_dstate->pmem_size, CXL_CAPACITY_MULTIPLIER)) ||
+        (!QEMU_IS_ALIGNED(ct3d->dc.total_capacity, CXL_CAPACITY_MULTIPLIER))) {
         return CXL_MBOX_INTERNAL_ERROR;
     }
 
@@ -1179,7 +1184,8 @@  static CXLRetCode cmd_media_clear_poison(const struct cxl_cmd *cmd,
     struct clear_poison_pl *in = (void *)payload_in;
 
     dpa = ldq_le_p(&in->dpa);
-    if (dpa + CXL_CACHE_LINE_SIZE > cxl_dstate->static_mem_size) {
+    if (dpa + CXL_CACHE_LINE_SIZE > cxl_dstate->static_mem_size +
+        ct3d->dc.total_capacity) {
         return CXL_MBOX_INVALID_PA;
     }
 
diff --git a/hw/mem/cxl_type3.c b/hw/mem/cxl_type3.c
index a1fe268560..ac87398089 100644
--- a/hw/mem/cxl_type3.c
+++ b/hw/mem/cxl_type3.c
@@ -45,7 +45,8 @@  enum {
 
 static void ct3_build_cdat_entries_for_mr(CDATSubHeader **cdat_table,
                                           int dsmad_handle, uint64_t size,
-                                          bool is_pmem, uint64_t dpa_base)
+                                          bool is_pmem, bool is_dynamic,
+                                          uint64_t dpa_base)
 {
     CDATDsmas *dsmas;
     CDATDslbis *dslbis0;
@@ -61,7 +62,8 @@  static void ct3_build_cdat_entries_for_mr(CDATSubHeader **cdat_table,
             .length = sizeof(*dsmas),
         },
         .DSMADhandle = dsmad_handle,
-        .flags = is_pmem ? CDAT_DSMAS_FLAG_NV : 0,
+        .flags = (is_pmem ? CDAT_DSMAS_FLAG_NV : 0) |
+                 (is_dynamic ? CDAT_DSMAS_FLAG_DYNAMIC_CAP : 0),
         .DPA_base = dpa_base,
         .DPA_length = size,
     };
@@ -149,12 +151,13 @@  static int ct3_build_cdat_table(CDATSubHeader ***cdat_table, void *priv)
     g_autofree CDATSubHeader **table = NULL;
     CXLType3Dev *ct3d = priv;
     MemoryRegion *volatile_mr = NULL, *nonvolatile_mr = NULL;
+    MemoryRegion *dc_mr = NULL;
     uint64_t vmr_size = 0, pmr_size = 0;
     int dsmad_handle = 0;
     int cur_ent = 0;
     int len = 0;
 
-    if (!ct3d->hostpmem && !ct3d->hostvmem) {
+    if (!ct3d->hostpmem && !ct3d->hostvmem && !ct3d->dc.num_regions) {
         return 0;
     }
 
@@ -176,21 +179,54 @@  static int ct3_build_cdat_table(CDATSubHeader ***cdat_table, void *priv)
         pmr_size = memory_region_size(nonvolatile_mr);
     }
 
+    if (ct3d->dc.num_regions) {
+        if (!ct3d->dc.host_dc) {
+            return -EINVAL;
+        }
+        dc_mr = host_memory_backend_get_memory(ct3d->dc.host_dc);
+        if (!dc_mr) {
+            return -EINVAL;
+        }
+        len += CT3_CDAT_NUM_ENTRIES * ct3d->dc.num_regions;
+    }
+
     table = g_malloc0(len * sizeof(*table));
 
     /* Now fill them in */
     if (volatile_mr) {
         ct3_build_cdat_entries_for_mr(table, dsmad_handle++, vmr_size,
-                                      false, 0);
+                                      false, false, 0);
         cur_ent = CT3_CDAT_NUM_ENTRIES;
     }
 
     if (nonvolatile_mr) {
         uint64_t base = vmr_size;
         ct3_build_cdat_entries_for_mr(&(table[cur_ent]), dsmad_handle++,
-                                      pmr_size, true, base);
+                                      pmr_size, true, false, base);
         cur_ent += CT3_CDAT_NUM_ENTRIES;
     }
+
+    if (dc_mr) {
+        int i;
+        uint64_t region_base = vmr_size + pmr_size;
+
+        /*
+         * TODO: we assume the dynamic capacity to be volatile for now.
+         * Non-volatile dynamic capacity will be added if needed in the
+         * future.
+         */
+        for (i = 0; i < ct3d->dc.num_regions; i++) {
+            ct3_build_cdat_entries_for_mr(&(table[cur_ent]),
+                                          dsmad_handle++,
+                                          ct3d->dc.regions[i].len,
+                                          false, true, region_base);
+            ct3d->dc.regions[i].dsmadhandle = dsmad_handle - 1;
+
+            cur_ent += CT3_CDAT_NUM_ENTRIES;
+            region_base += ct3d->dc.regions[i].len;
+        }
+    }
+
     assert(len == cur_ent);
 
     *cdat_table = g_steal_pointer(&table);
@@ -301,10 +337,16 @@  static void build_dvsecs(CXLType3Dev *ct3d)
             range2_size_lo = (2 << 5) | (2 << 2) | 0x3 |
                              (ct3d->hostpmem->size & 0xF0000000);
         }
-    } else {
+    } else if (ct3d->hostpmem) {
         range1_size_hi = ct3d->hostpmem->size >> 32;
         range1_size_lo = (2 << 5) | (2 << 2) | 0x3 |
                          (ct3d->hostpmem->size & 0xF0000000);
+    } else {
+        /*
+         * For DCD with no static memory, set memory active, memory class bits.
+         * No range is set.
+         */
+        range1_size_lo = (2 << 5) | (2 << 2) | 0x3;
     }
 
     dvsec = (uint8_t *)&(CXLDVSECDevice){
@@ -579,11 +621,27 @@  static bool cxl_create_dc_regions(CXLType3Dev *ct3d, Error **errp)
 {
     int i;
     uint64_t region_base = 0;
-    uint64_t region_len =  2 * GiB;
-    uint64_t decode_len = 2 * GiB;
+    uint64_t region_len;
+    uint64_t decode_len;
     uint64_t blk_size = 2 * MiB;
     CXLDCRegion *region;
     MemoryRegion *mr;
+    uint64_t dc_size;
+
+    mr = host_memory_backend_get_memory(ct3d->dc.host_dc);
+    dc_size = memory_region_size(mr);
+    region_len = DIV_ROUND_UP(dc_size, ct3d->dc.num_regions);
+
+    if (dc_size % (ct3d->dc.num_regions * CXL_CAPACITY_MULTIPLIER) != 0) {
+        error_setg(errp, "host backend size must be multiples of region len");
+        return false;
+    }
+    if (region_len % CXL_CAPACITY_MULTIPLIER != 0) {
+        error_setg(errp, "DC region size is unaligned to %lx",
+                   CXL_CAPACITY_MULTIPLIER);
+        return false;
+    }
+    decode_len = region_len;
 
     if (ct3d->hostvmem) {
         mr = host_memory_backend_get_memory(ct3d->hostvmem);
@@ -606,6 +664,7 @@  static bool cxl_create_dc_regions(CXLType3Dev *ct3d, Error **errp)
             /* dsmad_handle set when creating CDAT table entries */
             .flags = 0,
         };
+        ct3d->dc.total_capacity += region->len;
     }
 
     return true;
@@ -615,7 +674,8 @@  static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
 {
     DeviceState *ds = DEVICE(ct3d);
 
-    if (!ct3d->hostmem && !ct3d->hostvmem && !ct3d->hostpmem) {
+    if (!ct3d->hostmem && !ct3d->hostvmem && !ct3d->hostpmem
+        && !ct3d->dc.num_regions) {
         error_setg(errp, "at least one memdev property must be set");
         return false;
     } else if (ct3d->hostmem && ct3d->hostpmem) {
@@ -679,7 +739,37 @@  static bool cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
         g_free(p_name);
     }
 
+    ct3d->dc.total_capacity = 0;
     if (ct3d->dc.num_regions > 0) {
+        MemoryRegion *dc_mr;
+        char *dc_name;
+
+        if (!ct3d->dc.host_dc) {
+            error_setg(errp, "dynamic capacity must have a backing device");
+            return false;
+        }
+
+        dc_mr = host_memory_backend_get_memory(ct3d->dc.host_dc);
+        if (!dc_mr) {
+            error_setg(errp, "dynamic capacity must have a backing device");
+            return false;
+        }
+
+        /*
+         * TODO: set dc as volatile for now, non-volatile support can be added
+         * in the future if needed.
+         */
+        memory_region_set_nonvolatile(dc_mr, false);
+        memory_region_set_enabled(dc_mr, true);
+        host_memory_backend_set_mapped(ct3d->dc.host_dc, true);
+        if (ds->id) {
+            dc_name = g_strdup_printf("cxl-dcd-dpa-dc-space:%s", ds->id);
+        } else {
+            dc_name = g_strdup("cxl-dcd-dpa-dc-space");
+        }
+        address_space_init(&ct3d->dc.host_dc_as, dc_mr, dc_name);
+        g_free(dc_name);
+
         if (!cxl_create_dc_regions(ct3d, errp)) {
             error_setg(errp, "setup DC regions failed");
             return false;
@@ -776,6 +866,9 @@  err_release_cdat:
 err_free_special_ops:
     g_free(regs->special_ops);
 err_address_space_free:
+    if (ct3d->dc.host_dc) {
+        address_space_destroy(&ct3d->dc.host_dc_as);
+    }
     if (ct3d->hostpmem) {
         address_space_destroy(&ct3d->hostpmem_as);
     }
@@ -794,6 +887,9 @@  static void ct3_exit(PCIDevice *pci_dev)
     pcie_aer_exit(pci_dev);
     cxl_doe_cdat_release(cxl_cstate);
     g_free(regs->special_ops);
+    if (ct3d->dc.host_dc) {
+        address_space_destroy(&ct3d->dc.host_dc_as);
+    }
     if (ct3d->hostpmem) {
         address_space_destroy(&ct3d->hostpmem_as);
     }
@@ -872,16 +968,23 @@  static int cxl_type3_hpa_to_as_and_dpa(CXLType3Dev *ct3d,
                                        AddressSpace **as,
                                        uint64_t *dpa_offset)
 {
-    MemoryRegion *vmr = NULL, *pmr = NULL;
+    MemoryRegion *vmr = NULL, *pmr = NULL, *dc_mr = NULL;
+    uint64_t vmr_size = 0, pmr_size = 0, dc_size = 0;
 
     if (ct3d->hostvmem) {
         vmr = host_memory_backend_get_memory(ct3d->hostvmem);
+        vmr_size = memory_region_size(vmr);
     }
     if (ct3d->hostpmem) {
         pmr = host_memory_backend_get_memory(ct3d->hostpmem);
+        pmr_size = memory_region_size(pmr);
+    }
+    if (ct3d->dc.host_dc) {
+        dc_mr = host_memory_backend_get_memory(ct3d->dc.host_dc);
+        dc_size = memory_region_size(dc_mr);
     }
 
-    if (!vmr && !pmr) {
+    if (!vmr && !pmr && !dc_mr) {
         return -ENODEV;
     }
 
@@ -889,19 +992,18 @@  static int cxl_type3_hpa_to_as_and_dpa(CXLType3Dev *ct3d,
         return -EINVAL;
     }
 
-    if (*dpa_offset > ct3d->cxl_dstate.static_mem_size) {
+    if (*dpa_offset >= vmr_size + pmr_size + dc_size) {
         return -EINVAL;
     }
 
-    if (vmr) {
-        if (*dpa_offset < memory_region_size(vmr)) {
-            *as = &ct3d->hostvmem_as;
-        } else {
-            *as = &ct3d->hostpmem_as;
-            *dpa_offset -= memory_region_size(vmr);
-        }
-    } else {
+    if (*dpa_offset < vmr_size) {
+        *as = &ct3d->hostvmem_as;
+    } else if (*dpa_offset < vmr_size + pmr_size) {
         *as = &ct3d->hostpmem_as;
+        *dpa_offset -= vmr_size;
+    } else {
+        *as = &ct3d->dc.host_dc_as;
+        *dpa_offset -= (vmr_size + pmr_size);
     }
 
     return 0;
@@ -983,6 +1085,8 @@  static Property ct3_props[] = {
     DEFINE_PROP_UINT64("sn", CXLType3Dev, sn, UI64_NULL),
     DEFINE_PROP_STRING("cdat", CXLType3Dev, cxl_cstate.cdat.filename),
     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_END_OF_LIST(),
 };
 
@@ -1049,33 +1153,39 @@  static void set_lsa(CXLType3Dev *ct3d, const void *buf, uint64_t size,
 
 static bool set_cacheline(CXLType3Dev *ct3d, uint64_t dpa_offset, uint8_t *data)
 {
-    MemoryRegion *vmr = NULL, *pmr = NULL;
+    MemoryRegion *vmr = NULL, *pmr = NULL, *dc_mr = NULL;
     AddressSpace *as;
+    uint64_t vmr_size = 0, pmr_size = 0, dc_size = 0;
 
     if (ct3d->hostvmem) {
         vmr = host_memory_backend_get_memory(ct3d->hostvmem);
+        vmr_size = memory_region_size(vmr);
     }
     if (ct3d->hostpmem) {
         pmr = host_memory_backend_get_memory(ct3d->hostpmem);
+        pmr_size = memory_region_size(pmr);
     }
+    if (ct3d->dc.host_dc) {
+        dc_mr = host_memory_backend_get_memory(ct3d->dc.host_dc);
+        dc_size = memory_region_size(dc_mr);
+     }
 
-    if (!vmr && !pmr) {
+    if (!vmr && !pmr && !dc_mr) {
         return false;
     }
 
-    if (dpa_offset + CXL_CACHE_LINE_SIZE > ct3d->cxl_dstate.static_mem_size) {
+    if (dpa_offset + CXL_CACHE_LINE_SIZE > vmr_size + pmr_size + dc_size) {
         return false;
     }
 
-    if (vmr) {
-        if (dpa_offset < memory_region_size(vmr)) {
-            as = &ct3d->hostvmem_as;
-        } else {
-            as = &ct3d->hostpmem_as;
-            dpa_offset -= memory_region_size(vmr);
-        }
-    } else {
+    if (dpa_offset < vmr_size) {
+        as = &ct3d->hostvmem_as;
+    } else if (dpa_offset < vmr_size + pmr_size) {
         as = &ct3d->hostpmem_as;
+        dpa_offset -= vmr_size;
+    } else {
+        as = &ct3d->dc.host_dc_as;
+        dpa_offset -= (vmr_size + pmr_size);
     }
 
     address_space_write(as, dpa_offset, MEMTXATTRS_UNSPECIFIED, &data,
diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
index f7f56b44e3..c2c3df0d2a 100644
--- a/include/hw/cxl/cxl_device.h
+++ b/include/hw/cxl/cxl_device.h
@@ -467,6 +467,14 @@  struct CXLType3Dev {
     uint64_t poison_list_overflow_ts;
 
     struct dynamic_capacity {
+        HostMemoryBackend *host_dc;
+        AddressSpace host_dc_as;
+        /*
+         * total_capacity is equivalent to the dynamic capability
+         * memory region size.
+         */
+        uint64_t total_capacity; /* 256M aligned */
+
         uint8_t num_regions; /* 0-8 regions */
         CXLDCRegion regions[DCD_MAX_NUM_REGION];
     } dc;