On Thu, 22 May 2025, Vinayak Holikatti wrote:

CXL spec 3.2 section 7.6.7.5.2  describes Get Head Info.

So how was this tested? Ideally this now comes with a libcxlmi (or equivalent)
test case. See for example how Anisa is going about this with the FMAPI DCD
patches:

https://lore.kernel.org/linux-cxl/20250508001754.122180-1-anisa.su...@gmail.com/

Signed-off-by: Vinayak Holikatti <vinayak...@samsung.com>
---
This patch is generated against Jonathan Cameron's branch cxl-2025-03-20

Adding him to the thread :)


hw/cxl/cxl-mailbox-utils.c  | 21 +++++++++
hw/cxl/mhsld/mhsld.c        | 92 ++++++++++++++++++++++++++++++++++++-
hw/cxl/mhsld/mhsld.h        | 26 +++++++++++
include/hw/cxl/cxl_device.h |  6 +++
4 files changed, 144 insertions(+), 1 deletion(-)

diff --git a/hw/cxl/cxl-mailbox-utils.c b/hw/cxl/cxl-mailbox-utils.c
index a02d130926..4f25caecea 100644
--- a/hw/cxl/cxl-mailbox-utils.c
+++ b/hw/cxl/cxl-mailbox-utils.c
@@ -122,6 +122,7 @@ enum {
        #define MANAGEMENT_COMMAND     0x0
    MHD = 0x55,
        #define GET_MHD_INFO 0x0
+        #define GET_MHD_HEAD_INFO 0x1
};

/* CCI Message Format CXL r3.1 Figure 7-19 */
@@ -267,6 +268,23 @@ static CXLRetCode cmd_mhd_get_info(const struct cxl_cmd 
*cmd,
    return CXL_MBOX_UNSUPPORTED;
}

+/*
+ * CXL r3.2 section 7.6.7.5.2 - Get Multi-Headed Head Info (Opcode 5501h)
+ */
+static CXLRetCode cmd_mhd_get_head_info(const struct cxl_cmd *cmd,
+                                   uint8_t *payload_in, size_t len_in,
+                                   uint8_t *payload_out, size_t *len_out,
+                                   CXLCCI *cci)
+{
+    CXLType3Dev *ct3d = CXL_TYPE3(cci->d);
+    CXLType3Class *cvc = CXL_TYPE3_GET_CLASS(ct3d);
+    if (cvc->mhd_get_head_info) {
+        return cvc->mhd_get_head_info(cmd, payload_in, len_in, payload_out,
+                                 len_out, cci);
+    }
+    return CXL_MBOX_UNSUPPORTED;
+}
+
static CXLRetCode cmd_events_get_records(const struct cxl_cmd *cmd,
                                         uint8_t *payload_in, size_t len_in,
                                         uint8_t *payload_out, size_t *len_out,
@@ -3429,6 +3447,7 @@ static const struct cxl_cmd cxl_cmd_set[256][256] = {
        "MEDIA_AND_POISON_GET_SCAN_MEDIA_RESULTS",
        cmd_media_get_scan_media_results, 0, 0 },
    [MHD][GET_MHD_INFO] = { "GET_MULTI_HEADED_INFO", cmd_mhd_get_info, 2, 0},
+    [MHD][GET_MHD_HEAD_INFO] = { "GET_MULTI_HEADED_INFO", 
cmd_mhd_get_head_info, 2, 0},
};

static const struct cxl_cmd cxl_cmd_set_dcd[256][256] = {
@@ -3761,6 +3780,8 @@ static const struct cxl_cmd 
cxl_cmd_set_t3_fm_owned_ld_mctp[256][256] = {
    [TIMESTAMP][GET] = { "TIMESTAMP_GET", cmd_timestamp_get, 0, 0 },
    [TUNNEL][MANAGEMENT_COMMAND] = { "TUNNEL_MANAGEMENT_COMMAND",
                                     cmd_tunnel_management_cmd, ~0, 0 },
+    [MHD][GET_MHD_INFO] = { "GET_MULTI_HEADED_INFO", cmd_mhd_get_info, 2, 0},
+    [MHD][GET_MHD_HEAD_INFO] = { "GET_MULTI_HEADED_INFO", 
cmd_mhd_get_head_info, 2, 0},
};

void cxl_initialize_t3_fm_owned_ld_mctpcci(CXLCCI *cci, DeviceState *d,
diff --git a/hw/cxl/mhsld/mhsld.c b/hw/cxl/mhsld/mhsld.c
index 9f633b3bed..981546b5ff 100644
--- a/hw/cxl/mhsld/mhsld.c
+++ b/hw/cxl/mhsld/mhsld.c
@@ -61,9 +61,57 @@ static CXLRetCode cmd_mhd_get_info(const struct cxl_cmd *cmd,
    return CXL_MBOX_SUCCESS;
}

+/*
+ * CXL r3.2 section 7.6.7.5.2 - Get Head Info (Opcode 5501h)
+ *
+ * This command retrieves the number of heads, number of supported LDs,
+ * and Head-to-LD mapping of a Multi-Headed device.
+ */
+static CXLRetCode cmd_mhd_get_head_info(const struct cxl_cmd *cmd,
+                                        uint8_t *payload_in, size_t len_in,
+                                        uint8_t *payload_out, size_t *len_out,
+                                        CXLCCI *cci)
+{
+    CXLMHSLDState *s = CXL_MHSLD(cci->d);
+    MHDGetHeadInfoInput *input = (void *)payload_in;
+    MHDGetHeadInfoOutput *output = (void *)payload_out;
+    int i = 0;
+
+    if (input->start_head > MHSLD_HEADS) {
+        return CXL_MBOX_INVALID_INPUT;
+    }
+
+    output->nr_heads = MIN((MHSLD_HEADS - input->start_head), input->nr_heads);
+    for (i = input->start_head; i < input->start_head + output->nr_heads; i++) 
{
+        output->head_info_list[i].port_number =
+                                 s->mhd_state->head_info_blocks[i].port_number;
+        output->head_info_list[i].max_link_width =
+                              s->mhd_state->head_info_blocks[i].max_link_width;
+        output->head_info_list[i].nego_link_width =
+                             s->mhd_state->head_info_blocks[i].nego_link_width;
+        output->head_info_list[i].supp_link_speeds_vector =
+                     s->mhd_state->head_info_blocks[i].supp_link_speeds_vector;
+        output->head_info_list[i].max_link_speed =
+                              s->mhd_state->head_info_blocks[i].max_link_speed;
+        output->head_info_list[i].current_link_speed =
+                          s->mhd_state->head_info_blocks[i].current_link_speed;
+        output->head_info_list[i].ltssm_state =
+                                 s->mhd_state->head_info_blocks[i].ltssm_state;
+        output->head_info_list[i].first_nego_lane_num =
+                         s->mhd_state->head_info_blocks[i].first_nego_lane_num;
+        output->head_info_list[i].link_state_flags =
+                            s->mhd_state->head_info_blocks[i].link_state_flags;
+    }
+
+    *len_out = sizeof(*output) + output->nr_heads * sizeof(MHDHeadInfoBlock);
+    return CXL_MBOX_SUCCESS;
+}
+
static const struct cxl_cmd cxl_cmd_set_mhsld[256][256] = {
    [MHSLD_MHD][GET_MHD_INFO] = {"GET_MULTI_HEADED_INFO",
        cmd_mhd_get_info, 2, 0},
+    [MHSLD_MHD][GET_MHD_HEAD_INFO] = {"GET_HEAD_INFO",
+        cmd_mhd_get_head_info, 2, 0},
};

static const Property cxl_mhsld_props[] = {
@@ -166,6 +214,47 @@ static void cxl_mhsld_state_initialize(CXLMHSLDState *s, 
size_t dc_size)
    s->mhd_state->nr_blocks = dc_size / MHSLD_BLOCK_SZ;
}

+
+static void cxl_mhsld_init_head_info(CXLMHSLDState *s, PCIDevice *pdev)
+{
+    uint16_t lnksta = 0;
+    uint16_t current_link_speed = 0;
+    uint16_t negotiated_link_width = 0;
+    uint16_t lnkcap = 0, lnkcap2 = 0;
+    uint16_t max_link_width = 0;
+    uint16_t max_link_speed = 0;
+    uint16_t supported_link_speeds_vector = 0;
+
+    lnksta = pdev->config_read(pdev,
+                               pdev->exp.exp_cap + PCI_EXP_LNKSTA,
+                               sizeof(lnksta));
+    lnkcap = pdev->config_read(pdev,
+                               pdev->exp.exp_cap + PCI_EXP_LNKCAP,
+                               sizeof(lnkcap));
+    lnkcap2 = pdev->config_read(pdev,
+                                pdev->exp.exp_cap + PCI_EXP_LNKCAP2,
+                                sizeof(lnkcap2));
+    supported_link_speeds_vector = (lnkcap2 & 0xFE) >> 1;
+    max_link_width = (lnkcap & PCI_EXP_LNKCAP_MLW) >> 4;
+    max_link_speed = lnkcap & PCI_EXP_LNKCAP_SLS;
+    current_link_speed = lnksta & PCI_EXP_LNKSTA_CLS;
+    negotiated_link_width = (lnksta & PCI_EXP_LNKSTA_NLW) >> 4;
+
+    s->mhd_state->head_info_blocks[s->mhd_head].port_number = s->mhd_head;
+    s->mhd_state->head_info_blocks[s->mhd_head].max_link_width = 
max_link_width;
+    s->mhd_state->head_info_blocks[s->mhd_head].nego_link_width =
+                                                          
negotiated_link_width;
+    s->mhd_state->head_info_blocks[s->mhd_head].supp_link_speeds_vector =
+                                                   
supported_link_speeds_vector;
+    s->mhd_state->head_info_blocks[s->mhd_head].max_link_speed =
+                                                                 
max_link_speed;
+    s->mhd_state->head_info_blocks[s->mhd_head].current_link_speed =
+                                                             
current_link_speed;
+    s->mhd_state->head_info_blocks[s->mhd_head].ltssm_state = 0x7;
+    s->mhd_state->head_info_blocks[s->mhd_head].first_nego_lane_num = 0;
+    s->mhd_state->head_info_blocks[s->mhd_head].link_state_flags = 0;
+}
+
/* Returns starting index of region in MHD map. */
static inline size_t cxl_mhsld_find_dc_region_start(PCIDevice *d,
                                                    CXLDCRegion *r)
@@ -376,7 +465,7 @@ static void cxl_mhsld_realize(PCIDevice *pci_dev, Error 
**errp)
    }

    cxl_mhsld_state_initialize(s, dc_size);
-
+    cxl_mhsld_init_head_info(s, pci_dev);
    /* Set the LD ownership for this head to this system */
    s->mhd_state->ldmap[s->mhd_head] = s->mhd_head;
    return;
@@ -428,6 +517,7 @@ static void cxl_mhsld_class_init(ObjectClass *klass, void 
*data)

    CXLType3Class *cvc = CXL_TYPE3_CLASS(klass);
    cvc->mhd_get_info = cmd_mhd_get_info;
+    cvc->mhd_get_head_info = cmd_mhd_get_head_info;
    cvc->mhd_access_valid = cxl_mhsld_access_valid;
    cvc->mhd_reserve_extents = cxl_mhsld_reserve_extents;
    cvc->mhd_reclaim_extents = cxl_mhsld_reclaim_extents;
diff --git a/hw/cxl/mhsld/mhsld.h b/hw/cxl/mhsld/mhsld.h
index e7ead1f0d2..c9fbec71ca 100644
--- a/hw/cxl/mhsld/mhsld.h
+++ b/hw/cxl/mhsld/mhsld.h
@@ -23,6 +23,18 @@
 */
#define MHSLD_HEADS  (8)

+typedef struct MHDHeadInfoBlock {
+    uint8_t port_number;
+    uint8_t max_link_width;
+    uint8_t nego_link_width;
+    uint8_t supp_link_speeds_vector;
+    uint8_t max_link_speed;
+    uint8_t current_link_speed;
+    uint8_t ltssm_state;
+    uint8_t first_nego_lane_num;
+    uint8_t link_state_flags;
+} QEMU_PACKED MHDHeadInfoBlock;
+
/*
 * The shared state cannot have 2 variable sized regions
 * so we have to max out the ldmap.
@@ -32,6 +44,7 @@ typedef struct MHSLDSharedState {
    uint8_t nr_lds;
    uint8_t ldmap[MHSLD_HEADS];
    uint64_t nr_blocks;
+    MHDHeadInfoBlock head_info_blocks[MHSLD_HEADS];
    uint8_t blocks[];
} MHSLDSharedState;

@@ -52,6 +65,7 @@ struct CXLMHSLDClass {
enum {
    MHSLD_MHD = 0x55,
        #define GET_MHD_INFO 0x0
+        #define GET_MHD_HEAD_INFO 0x1
};

/*
@@ -72,4 +86,16 @@ typedef struct MHDGetInfoOutput {
    uint16_t resv2;
    uint8_t ldmap[];
} QEMU_PACKED MHDGetInfoOutput;
+
+typedef struct MHDGetHeadInfoInput {
+    uint8_t start_head;
+    uint8_t nr_heads;
+} QEMU_PACKED MHDGetHeadInfoInput;
+
+typedef struct MHDGetHeadInfoOutput {
+    uint8_t nr_heads;
+    uint8_t rsvd[3];
+    MHDHeadInfoBlock head_info_list[];
+} QEMU_PACKED MHDGetHeadInfoOutput;
+
#endif
diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
index ca515cab13..c93c71c45d 100644
--- a/include/hw/cxl/cxl_device.h
+++ b/include/hw/cxl/cxl_device.h
@@ -732,6 +732,12 @@ struct CXLType3Class {
                               uint8_t *payload_out,
                               size_t *len_out,
                               CXLCCI *cci);
+    CXLRetCode (*mhd_get_head_info)(const struct cxl_cmd *cmd,
+                               uint8_t *payload_in,
+                               size_t len_in,
+                               uint8_t *payload_out,
+                               size_t *len_out,
+                               CXLCCI *cci);
    bool (*mhd_access_valid)(PCIDevice *d, uint64_t addr, unsigned int size);
    bool (*mhd_reserve_extents)(PCIDevice *d,
                                CxlDynamicCapacityExtentList *records,
--
2.34.1


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