Re: [PATCH 2/4] hw/cxl: Add get scan media capabilities cmd support

[Fan Ni <fan.ni@gmx.us>]

On Fri, Sep 08, 2023 at 12:31:50AM -0700, Davidlohr Bueso wrote:
> Use simple heuristics to determine the cost of scanning any given
> chunk, assuming cost is equal across the whole device, without
> differentiating between volatile or persistent partitions. This
> is aligned to the fact that these constraints are not enforced
> in respective poison query commands.
>
> Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
> ---
>  hw/cxl/cxl-mailbox-utils.c | 53 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
>
> diff --git a/hw/cxl/cxl-mailbox-utils.c b/hw/cxl/cxl-mailbox-utils.c
> index 4e8651ebe2e9..3073222060ab 100644
> --- a/hw/cxl/cxl-mailbox-utils.c
> +++ b/hw/cxl/cxl-mailbox-utils.c
> @@ -80,6 +80,7 @@ enum {
>          #define GET_POISON_LIST        0x0
>          #define INJECT_POISON          0x1
>          #define CLEAR_POISON           0x2
> +        #define GET_SCAN_MEDIA_CAPABILITIES 0x3
>      DCD_CONFIG  = 0x48,
>          #define GET_DC_CONFIG          0x0
>          #define GET_DYN_CAP_EXT_LIST   0x1
> @@ -1174,6 +1175,56 @@ static CXLRetCode cmd_media_clear_poison(const struct cxl_cmd *cmd,
>      return CXL_MBOX_SUCCESS;
>  }
>
> +/*
> + * CXL r3.0 section 8.2.9.8.4.4: Get Scan Media Capabilities
> + */
> +static CXLRetCode
> +cmd_media_get_scan_media_capabilities(const struct cxl_cmd *cmd,
> +                                      uint8_t *payload_in,
> +                                      size_t len_in,
> +                                      uint8_t *payload_out,
> +                                      size_t *len_out,
> +                                      CXLCCI *cci)
> +{
> +    struct get_scan_media_capabilities_pl {
> +        uint64_t pa;
> +        uint64_t length;
> +    } QEMU_PACKED;
> +
> +    struct get_scan_media_capabilities_out_pl {
> +        uint32_t estimated_runtime_ms;
> +    } QEMU_PACKED;
> +
> +    CXLType3Dev *ct3d = CXL_TYPE3(cci->d);
> +    CXLDeviceState *cxl_dstate = &ct3d->cxl_dstate;
> +    struct get_scan_media_capabilities_pl *in = (void *)payload_in;
> +    struct get_scan_media_capabilities_out_pl *out = (void *)payload_out;
> +    uint64_t query_start;
> +    uint64_t query_length;
> +
> +    query_start = ldq_le_p(&in->pa);
> +    /* 64 byte alignment required */
> +    if (query_start & 0x3f) {
> +        return CXL_MBOX_INVALID_INPUT;

From the spec, it is not clear to me whether we should return invalid
input or invalid PA.

Fan

> +    }
> +    query_length = ldq_le_p(&in->length) * CXL_CACHE_LINE_SIZE;
> +
> +    if (query_start + query_length > cxl_dstate->static_mem_size) {
> +        return CXL_MBOX_INVALID_PA;
> +    }
> +
> +    /*
> +     * Just use 400 nanosecond access/read latency + 100 ns for
> +     * the cost of updating the poison list. For small enough
> +     * chunks return at least 1 ms.
> +     */
> +    stl_le_p(&out->estimated_runtime_ms,
> +             MAX(1, query_length * (0.0005L/64)));
> +
> +    *len_out = sizeof(*out);
> +    return CXL_MBOX_SUCCESS;
> +}
> +
>  /*
>   * CXL r3.0 section 8.2.9.8.9.1: Dynamic Capacity Configuration
>   */
> @@ -1602,6 +1653,8 @@ static const struct cxl_cmd cxl_cmd_set[256][256] = {
>          cmd_media_inject_poison, 8, 0 },
>      [MEDIA_AND_POISON][CLEAR_POISON] = { "MEDIA_AND_POISON_CLEAR_POISON",
>          cmd_media_clear_poison, 72, 0 },
> +    [MEDIA_AND_POISON][GET_SCAN_MEDIA_CAPABILITIES] = { "MEDIA_AND_POISON_GET_SCAN_MEDIA_CAPABILITIES",
> +        cmd_media_get_scan_media_capabilities, 16, 0 },
>  };
>
>  static const struct cxl_cmd cxl_cmd_set_dcd[256][256] = {
> --
> 2.42.0
>