1 files changed, 69 insertions, 0 deletions
diff --git a/hw/acpi/cxl.c b/hw/acpi/cxl.c
index 92b46bc932..9cd7905ea2 100644
--- a/hw/acpi/cxl.c
+++ b/hw/acpi/cxl.c
@@ -30,6 +30,75 @@
 #include "qapi/error.h"
 #include "qemu/uuid.h"
 
+void build_cxl_dsm_method(Aml *dev)
+{
+    Aml *method, *ifctx, *ifctx2;
+
+    method = aml_method("_DSM", 4, AML_SERIALIZED);
+    {
+        Aml *function, *uuid;
+
+        uuid = aml_arg(0);
+        function = aml_arg(2);
+        /* CXL spec v3.0 9.17.3.1 _DSM Function for Retrieving QTG ID */
+        ifctx = aml_if(aml_equal(
+            uuid, aml_touuid("F365F9A6-A7DE-4071-A66A-B40C0B4F8E52")));
+
+        /* Function 0, standard DSM query function */
+        ifctx2 = aml_if(aml_equal(function, aml_int(0)));
+        {
+            uint8_t byte_list[1] = { 0x01 }; /* function 1 only */
+
+            aml_append(ifctx2,
+                       aml_return(aml_buffer(sizeof(byte_list), byte_list)));
+        }
+        aml_append(ifctx, ifctx2);
+
+        /*
+         * Function 1
+         * Creating a package with static values. The max supported QTG ID will
+         * be 1 and recommended QTG IDs are 0 and then 1.
+         * The values here are statically created to simplify emulation. Values
+         * from a real BIOS would be determined by the performance of all the
+         * present CXL memory and then assigned.
+         */
+        ifctx2 = aml_if(aml_equal(function, aml_int(1)));
+        {
+            Aml *pak, *pak1;
+
+            /*
+             * Return: A package containing two elements - a WORD that returns
+             * the maximum throttling group that the platform supports, and a
+             * package containing the QTG ID(s) that the platform recommends.
+             * Package {
+             *     Max Supported QTG ID
+             *     Package {QTG Recommendations}
+             * }
+             *
+             * While the SPEC specified WORD that hints at the value being
+             * 16bit, the ACPI dump of BIOS DSDT table showed that the values
+             * are integers with no specific size specification. aml_int() will
+             * be used for the values.
+             */
+            pak1 = aml_package(2);
+            /* Set QTG ID of 0 */
+            aml_append(pak1, aml_int(0));
+            /* Set QTG ID of 1 */
+            aml_append(pak1, aml_int(1));
+
+            pak = aml_package(2);
+            /* Set Max QTG 1 */
+            aml_append(pak, aml_int(1));
+            aml_append(pak, pak1);
+
+            aml_append(ifctx2, aml_return(pak));
+        }
+        aml_append(ifctx, ifctx2);
+    }
+    aml_append(method, ifctx);
+    aml_append(dev, method);
+}
+
 static void cedt_build_chbs(GArray *table_data, PXBCXLDev *cxl)
 {
     PXBDev *pxb = PXB_DEV(cxl);