hw/cxl: Support get/set mctp response payload size

Add Get/Set Response Message Limit commands.

Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20250305092501.191929-3-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/cxl/cxl-mailbox-utils.c

@@ -7,6 +7,8 @@
  * COPYING file in the top-level directory.
  */
 
+#include <math.h>
+
 #include "qemu/osdep.h"
 #include "hw/pci/msi.h"
 #include "hw/pci/msix.h"
@@ -56,6 +58,8 @@ enum {
     INFOSTAT    = 0x00,
         #define IS_IDENTIFY   0x1
         #define BACKGROUND_OPERATION_STATUS    0x2
+        #define GET_RESPONSE_MSG_LIMIT         0x3
+        #define SET_RESPONSE_MSG_LIMIT         0x4
         #define BACKGROUND_OPERATION_ABORT     0x5
     EVENTS      = 0x01,
         #define GET_RECORDS   0x0
@@ -413,12 +417,58 @@ static CXLRetCode cmd_infostat_identify(const struct cxl_cmd *cmd,
         is_identify->component_type = 0x3; /* Type 3 */
     }
 
-    /* TODO: Allow this to vary across different CCIs */
-    is_identify->max_message_size = 9; /* 512 bytes - MCTP_CXL_MAILBOX_BYTES */
+    is_identify->max_message_size = (uint8_t)log2(cci->payload_max);
     *len_out = sizeof(*is_identify);
     return CXL_MBOX_SUCCESS;
 }
 
+/* CXL r3.1 section 8.2.9.1.3: Get Response Message Limit (Opcode 0003h) */
+static CXLRetCode cmd_get_response_msg_limit(const struct cxl_cmd *cmd,
+                                             uint8_t *payload_in,
+                                             size_t len_in,
+                                             uint8_t *payload_out,
+                                             size_t *len_out,
+                                             CXLCCI *cci)
+{
+    struct {
+        uint8_t rsp_limit;
+    } QEMU_PACKED *get_rsp_msg_limit = (void *)payload_out;
+    QEMU_BUILD_BUG_ON(sizeof(*get_rsp_msg_limit) != 1);
+
+    get_rsp_msg_limit->rsp_limit = (uint8_t)log2(cci->payload_max);
+
+    *len_out = sizeof(*get_rsp_msg_limit);
+    return CXL_MBOX_SUCCESS;
+}
+
+/* CXL r3.1 section 8.2.9.1.4: Set Response Message Limit (Opcode 0004h) */
+static CXLRetCode cmd_set_response_msg_limit(const struct cxl_cmd *cmd,
+                                             uint8_t *payload_in,
+                                             size_t len_in,
+                                             uint8_t *payload_out,
+                                             size_t *len_out,
+                                             CXLCCI *cci)
+{
+    struct {
+        uint8_t rsp_limit;
+    } QEMU_PACKED *in = (void *)payload_in;
+    QEMU_BUILD_BUG_ON(sizeof(*in) != 1);
+    struct {
+        uint8_t rsp_limit;
+    } QEMU_PACKED *out = (void *)payload_out;
+    QEMU_BUILD_BUG_ON(sizeof(*out) != 1);
+
+    if (in->rsp_limit < 8 || in->rsp_limit > 10) {
+        return CXL_MBOX_INVALID_INPUT;
+    }
+
+    cci->payload_max = 1 << in->rsp_limit;
+    out->rsp_limit = in->rsp_limit;
+
+    *len_out = sizeof(*out);
+    return CXL_MBOX_SUCCESS;
+}
+
 static void cxl_set_dsp_active_bm(PCIBus *b, PCIDevice *d,
                                   void *private)
 {
@@ -3105,6 +3155,10 @@ void cxl_initialize_t3_ld_cci(CXLCCI *cci, DeviceState *d, DeviceState *intf,
 
 static const struct cxl_cmd cxl_cmd_set_t3_fm_owned_ld_mctp[256][256] = {
     [INFOSTAT][IS_IDENTIFY] = { "IDENTIFY", cmd_infostat_identify, 0,  0},
+    [INFOSTAT][GET_RESPONSE_MSG_LIMIT] = { "GET_RESPONSE_MSG_LIMIT",
+                                           cmd_get_response_msg_limit, 0, 0 },
+    [INFOSTAT][SET_RESPONSE_MSG_LIMIT] = { "SET_RESPONSE_MSG_LIMIT",
+                                           cmd_set_response_msg_limit, 1, 0 },
     [LOGS][GET_SUPPORTED] = { "LOGS_GET_SUPPORTED", cmd_logs_get_supported, 0,
                               0 },
     [LOGS][GET_LOG] = { "LOGS_GET_LOG", cmd_logs_get_log, 0x18, 0 },