Re: [PATCH v2 qemu] hw/cxl/device: read from register values in mdev_reg_read()

[fan <nifan.cxl@gmail.com>]

On Thu, Jan 11, 2024 at 02:59:05PM +0000, Jonathan Cameron wrote:
> From: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> 
> In the current mdev_reg_read() implementation, it consistently returns
> that the Media Status is Ready (01b). This was fine until commit
> 25a52959f99d ("hw/cxl: Add support for device sanitation") because the
> media was presumed to be ready.
> 
> However, as per the CXL 3.0 spec "8.2.9.8.5.1 Sanitize (Opcode 4400h)",
> during sanitation, the Media State should be set to Disabled (11b). The
> mentioned commit correctly sets it to Disabled, but mdev_reg_read()
> still returns Media Status as Ready.
> 
> To address this, update mdev_reg_read() to read register values instead
> of returning dummy values.
> 
> Note __toggle_media() was overwriting the mailbox capability
> register, but nothing was reading that after this so that bug had no
> obvious effect unless the driver was reloaded.
> 
> Fixes: commit 25a52959f99d ("hw/cxl: Add support for device sanitation")
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> Link: https://lore.kernel.org/r/20231222090051.3265307-3-42.hyeyoo@gmail.com
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 

Reviewed-by: Fan Ni <fan.ni@samsung.com>

> --
> 
> Hyeonggon - I've kept your sign-off. Let me know if this is ok.
> Dropped RBs etc as this has changed quite a bit.
> 
> I plan to send out a group of fixes including this soon, but given
> I've been pointing out the original fix didn't work thought I'd send
> this one out for early review!
> 
> ---
>  include/hw/cxl/cxl_device.h |  9 +++++++--
>  hw/cxl/cxl-device-utils.c   | 17 +++++++++++------
>  2 files changed, 18 insertions(+), 8 deletions(-)
> 
> diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> index befb5f884b..31d2afcd3d 100644
> --- a/include/hw/cxl/cxl_device.h
> +++ b/include/hw/cxl/cxl_device.h
> @@ -202,6 +202,9 @@ typedef struct cxl_device_state {
>          };
>      };
>  
> +    /* Stash the memory device status value */
> +    uint64_t memdev_status;
> +
>      struct {
>          bool set;
>          uint64_t last_set;
> @@ -353,8 +356,10 @@ static inline void __toggle_media(CXLDeviceState *cxl_dstate, int val)
>  {
>      uint64_t dev_status_reg;
>  
> -    dev_status_reg = FIELD_DP64(0, CXL_MEM_DEV_STS, MEDIA_STATUS, val);
> -    cxl_dstate->mbox_reg_state64[R_CXL_MEM_DEV_STS] = dev_status_reg;
> +    dev_status_reg = cxl_dstate->memdev_status;
> +    dev_status_reg = FIELD_DP64(dev_status_reg, CXL_MEM_DEV_STS, MEDIA_STATUS,
> +                                val);
> +    cxl_dstate->memdev_status = dev_status_reg;
>  }
>  #define cxl_dev_disable_media(cxlds)                    \
>          do { __toggle_media((cxlds), 0x3); } while (0)
> diff --git a/hw/cxl/cxl-device-utils.c b/hw/cxl/cxl-device-utils.c
> index 61a3c4dc2e..40b619ffd9 100644
> --- a/hw/cxl/cxl-device-utils.c
> +++ b/hw/cxl/cxl-device-utils.c
> @@ -229,12 +229,9 @@ static void mailbox_reg_write(void *opaque, hwaddr offset, uint64_t value,
>  
>  static uint64_t mdev_reg_read(void *opaque, hwaddr offset, unsigned size)
>  {
> -    uint64_t retval = 0;
> -
> -    retval = FIELD_DP64(retval, CXL_MEM_DEV_STS, MEDIA_STATUS, 1);
> -    retval = FIELD_DP64(retval, CXL_MEM_DEV_STS, MBOX_READY, 1);
> +    CXLDeviceState *cxl_dstate = opaque;
>  
> -    return retval;
> +    return cxl_dstate->memdev_status;
>  }
>  
>  static void ro_reg_write(void *opaque, hwaddr offset, uint64_t value,
> @@ -371,7 +368,15 @@ static void mailbox_reg_init_common(CXLDeviceState *cxl_dstate)
>      cxl_dstate->mbox_msi_n = msi_n;
>  }
>  
> -static void memdev_reg_init_common(CXLDeviceState *cxl_dstate) { }
> +static void memdev_reg_init_common(CXLDeviceState *cxl_dstate)
> +{
> +    uint64_t memdev_status_reg;
> +
> +    memdev_status_reg = FIELD_DP64(0, CXL_MEM_DEV_STS, MEDIA_STATUS, 1);
> +    memdev_status_reg = FIELD_DP64(memdev_status_reg, CXL_MEM_DEV_STS,
> +                                   MBOX_READY, 1);
> +    cxl_dstate->memdev_status = memdev_status_reg;
> +}
>  
>  void cxl_device_register_init_t3(CXLType3Dev *ct3d)
>  {
> -- 
> 2.39.2
>