Re: [PATCH v4 09/42] hw/cxl/device: Timestamp implementation (8.2.9.3)

["Alex Bennée" <alex.bennee@linaro.org>]

Jonathan Cameron <Jonathan.Cameron@huawei.com> writes:

> From: Ben Widawsky <ben.widawsky@intel.com>
>
> Per spec, timestamp appears to be a free-running counter from a value
> set by the host via the Set Timestamp command (0301h). There are
> references to the epoch, which seem like a red herring. Therefore, the
> implementation implements the timestamp as freerunning counter from the
> last value that was issued by the Set Timestamp command.
>
> Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
>  hw/cxl/cxl-mailbox-utils.c  | 53 +++++++++++++++++++++++++++++++++++++
>  include/hw/cxl/cxl_device.h |  6 +++++
>  2 files changed, 59 insertions(+)
>
> diff --git a/hw/cxl/cxl-mailbox-utils.c b/hw/cxl/cxl-mailbox-utils.c
> index 1a87846356..cea4b2a59c 100644
> --- a/hw/cxl/cxl-mailbox-utils.c
> +++ b/hw/cxl/cxl-mailbox-utils.c
> @@ -43,6 +43,9 @@ enum {
>          #define CLEAR_RECORDS   0x1
>          #define GET_INTERRUPT_POLICY   0x2
>          #define SET_INTERRUPT_POLICY   0x3
> +    TIMESTAMP   = 0x03,
> +        #define GET           0x0
> +        #define SET           0x1
>  };
>  
>  /* 8.2.8.4.5.1 Command Return Codes */
> @@ -117,8 +120,11 @@ define_mailbox_handler_zeroed(EVENTS_GET_RECORDS, 0x20);
>  define_mailbox_handler_nop(EVENTS_CLEAR_RECORDS);
>  define_mailbox_handler_zeroed(EVENTS_GET_INTERRUPT_POLICY, 4);
>  define_mailbox_handler_nop(EVENTS_SET_INTERRUPT_POLICY);
> +declare_mailbox_handler(TIMESTAMP_GET);
> +declare_mailbox_handler(TIMESTAMP_SET);
>  
>  #define IMMEDIATE_CONFIG_CHANGE (1 << 1)
> +#define IMMEDIATE_POLICY_CHANGE (1 << 3)
>  #define IMMEDIATE_LOG_CHANGE (1 << 4)
>  
>  #define CXL_CMD(s, c, in, cel_effect) \
> @@ -129,10 +135,57 @@ static struct cxl_cmd cxl_cmd_set[256][256] = {
>      CXL_CMD(EVENTS, CLEAR_RECORDS, ~0, IMMEDIATE_LOG_CHANGE),
>      CXL_CMD(EVENTS, GET_INTERRUPT_POLICY, 0, 0),
>      CXL_CMD(EVENTS, SET_INTERRUPT_POLICY, 4, IMMEDIATE_CONFIG_CHANGE),
> +    CXL_CMD(TIMESTAMP, GET, 0, 0),
> +    CXL_CMD(TIMESTAMP, SET, 8, IMMEDIATE_POLICY_CHANGE),
>  };
>  
>  #undef CXL_CMD
>  
> +/*
> + * 8.2.9.3.1
> + */
> +define_mailbox_handler(TIMESTAMP_GET)
> +{
> +    struct timespec ts;
> +    uint64_t delta;
> +
> +    if (!cxl_dstate->timestamp.set) {
> +        *(uint64_t *)cmd->payload = 0;
> +        goto done;
> +    }
> +
> +    /* First find the delta from the last time the host set the time. */
> +    clock_gettime(CLOCK_REALTIME, &ts);

Could you consider using qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL)?
Otherwise by introducing a dependency on real time you'll loose the
ability to get deterministic execution via icount. 

> +    delta = (ts.tv_sec * NANOSECONDS_PER_SECOND + ts.tv_nsec) -
> +            cxl_dstate->timestamp.last_set;
> +
> +    /* Then adjust the actual time */
> +    stq_le_p(cmd->payload, cxl_dstate->timestamp.host_set + delta);
> +
> +done:
> +    *len = 8;
> +    return CXL_MBOX_SUCCESS;
> +}
> +
> +/*
> + * 8.2.9.3.2
> + */
> +define_mailbox_handler(TIMESTAMP_SET)
> +{
> +    struct timespec ts;
> +
> +    clock_gettime(CLOCK_REALTIME, &ts);
> +
> +    cxl_dstate->timestamp.set = true;
> +    cxl_dstate->timestamp.last_set =
> +        ts.tv_sec * NANOSECONDS_PER_SECOND + ts.tv_nsec;
> +
> +    cxl_dstate->timestamp.host_set = le64_to_cpu(*(uint64_t *)cmd->payload);
> +
> +    *len = 0;
> +    return CXL_MBOX_SUCCESS;
> +}
> +
>  QemuUUID cel_uuid;
>  
>  void cxl_process_mailbox(CXLDeviceState *cxl_dstate)
> diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> index f88f844cb6..3dde7fb1fb 100644
> --- a/include/hw/cxl/cxl_device.h
> +++ b/include/hw/cxl/cxl_device.h
> @@ -114,6 +114,12 @@ typedef struct cxl_device_state {
>          size_t cel_size;
>      };
>  
> +    struct {
> +        bool set;
> +        uint64_t last_set;
> +        uint64_t host_set;
> +    } timestamp;
> +
>      /* memory region for persistent memory, HDM */
>      uint64_t pmem_size;
>  } CXLDeviceState;


-- 
Alex Bennée