Re: [PATCH v2 2/4] x86: add domctl cmd to set/get CDP code/data CBM

[Chao Peng <chao.p.peng@linux.intel.com>]

On Wed, Sep 09, 2015 at 01:16:46PM +0800, He Chen wrote:
> CDP extends CAT and provides the capacity to control L3 code & data
> cache. With CDP, one COS correspond to two CMBs(code & data). cbm_type
> is added to support distinguish different CBM operation. Besides, new
> domctl cmds are introdunced to support set/get CDP CBM. Some CAT
> functions to operation CBMs are extended to support CDP.
> 
> Signed-off-by: He Chen <he.chen@linux.intel.com>
> ---
>  xen/arch/x86/domctl.c       |  32 ++++++++-
>  xen/arch/x86/psr.c          | 163 ++++++++++++++++++++++++++++++++++----------
>  xen/include/asm-x86/psr.h   |  12 +++-
>  xen/include/public/domctl.h |   4 ++
>  4 files changed, 170 insertions(+), 41 deletions(-)
> 
> diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
> index bf62a88..734fddb 100644
> --- a/xen/arch/x86/domctl.c
>  
> -int psr_get_l3_cbm(struct domain *d, unsigned int socket, uint64_t *cbm)
> +int psr_get_l3_cbm(struct domain *d, unsigned int socket,
> +                   uint64_t *cbm, enum cbm_type type)
>  {
>      struct psr_cat_socket_info *info = get_cat_socket_info(socket);
>  
>      if ( IS_ERR(info) )
>          return PTR_ERR(info);
>  
> -    *cbm = info->cos_to_cbm[d->arch.psr_cos_ids[socket]].u.cbm;
> +    if ( type == PSR_CBM_TYPE_L3 )
> +    {
> +        if ( info->cdp_enabled )
> +            return -EXDEV;
> +        *cbm = info->cos_to_cbm[d->arch.psr_cos_ids[socket]].u.cbm;
> +    }
> +    else if ( type == PSR_CBM_TYPE_L3_CODE )
> +    {
> +        if ( !info->cdp_enabled )
> +            return -EXDEV;
> +        *cbm = info->cos_to_cbm[d->arch.psr_cos_ids[socket]].u.cdp.code;
> +    }
> +    else
> +    {
> +        if ( !info->cdp_enabled )
> +            return -EXDEV;
> +        *cbm = info->cos_to_cbm[d->arch.psr_cos_ids[socket]].u.cdp.data;
> +    }

Could I suggest to use switch? And the check can be done in advance.

>  
>      return 0;
>  }
> @@ -371,65 +389,136 @@ static int write_l3_cbm(unsigned int socket, unsigned int cos,
>      return 0;
>  }
>  
> -int psr_set_l3_cbm(struct domain *d, unsigned int socket, uint64_t cbm)
> +static int find_cos(struct psr_cat_cbm *map, int cos_max,
> +                    uint64_t cbm_code, uint64_t cbm_data, bool_t cdp_enabled)
>  {
> -    unsigned int old_cos, cos;
> -    struct psr_cat_cbm *map, *found = NULL;
> +    unsigned int cos;
> +
> +    if ( !cdp_enabled )
> +    {
> +        for ( cos = 0; cos <= cos_max; cos++ )
> +            if ( map[cos].ref && map[cos].u.cbm == cbm_code )
> +                return cos;
> +    }
> +    else
> +    {
> +        for ( cos = 0; cos <= cos_max; cos++ )
> +            if ( map[cos].ref && map[cos].u.cdp.code == cbm_code &&
> +                 map[cos].u.cdp.data == cbm_data )
> +                return cos;
> +    }

I guess the '{' and '}' can be omitted if the body contains only one
sentence.

> +
> +    return -ENOENT;
> +}
> +
> +static int pick_avail_cos(struct psr_cat_cbm *map, int cos_max, int old_cos)
> +{
> +    int cos;
> +
> +    /* If old cos is referred only by the domain, then use it. */
> +    if ( map[old_cos].ref == 1 )
> +        return old_cos;
> +
> +    /* Then we pick an unused one, never pick 0 */

Find an unused one other than cos0.

> +    for ( cos = 1; cos <= cos_max; cos++ )
> +        if ( map[cos].ref == 0 )
> +            return cos;
> +
> +    return -ENOENT;
> +}
> +
> +int psr_set_l3_cbm(struct domain *d, unsigned int socket,
> +                   uint64_t cbm, enum cbm_type type)
> +{
> +    unsigned int old_cos, cos_max;
> +    int cos, ret;
> +    uint64_t cbm_data, cbm_code;
> +    bool_t need_write = 1;
> +    struct psr_cat_cbm *map;
>      struct psr_cat_socket_info *info = get_cat_socket_info(socket);
>  
>      if ( IS_ERR(info) )
>          return PTR_ERR(info);
>  
> +    cbm_code = (1ull << info->cbm_len) - 1;
> +    cbm_data = (1ull << info->cbm_len) - 1;

Why this is needed, as you will give them the value eventually.

>      if ( !psr_check_cbm(info->cbm_len, cbm) )
>          return -EINVAL;
>  
> +    cos_max = info->cos_max;
>      old_cos = d->arch.psr_cos_ids[socket];
>      map = info->cos_to_cbm;
>  
> -    spin_lock(&info->cbm_lock);
> -
> -    for ( cos = 0; cos <= info->cos_max; cos++ )
> +    switch( type )

Coding style.

Chao
>      {
> -        /* If still not found, then keep unused one. */
> -        if ( !found && cos != 0 && map[cos].ref == 0 )
> -            found = map + cos;
> -        else if ( map[cos].u.cbm == cbm )
> -        {
> -            if ( unlikely(cos == old_cos) )
> -            {
> -                ASSERT(cos == 0 || map[cos].ref != 0);
> -                spin_unlock(&info->cbm_lock);
> -                return 0;
> -            }
> -            found = map + cos;
> +        case PSR_CBM_TYPE_L3:
> +            if ( info->cdp_enabled )
> +                return -EINVAL;
> +            cbm_code = cbm;
> +            cbm_data = cbm;
>              break;
> -        }
> -    }
>  
> -    /* If old cos is referred only by the domain, then use it. */
> -    if ( !found && map[old_cos].ref == 1 )
> -        found = map + old_cos;
> +        case PSR_CBM_TYPE_L3_CODE:
> +            if ( !info->cdp_enabled )
> +                return -EINVAL;
> +            cbm_code = cbm;
> +            cbm_data = map[old_cos].u.cdp.data;
> +            break;
>  
> -    if ( !found )
> -    {
> -        spin_unlock(&info->cbm_lock);
> -        return -EOVERFLOW;
> +        case PSR_CBM_TYPE_L3_DATA:
> +            if ( !info->cdp_enabled )
> +                return -EINVAL;
> +            cbm_code = map[old_cos].u.cdp.code;
> +            cbm_data = cbm;
> +            break;
> +
> +        default:
> +            return -EINVAL;
>      }
>  
> -    cos = found - map;
> -    if ( found->u.cbm != cbm )
> +    spin_lock(&info->cbm_lock);
> +    cos = find_cos(map, cos_max, cbm_code, cbm_data, info->cdp_enabled);
> +    if ( cos >= 0 )
>      {
> -        int ret = write_l3_cbm(socket, cos, cbm, 0, 0);
> -
> -        if ( ret )
> +        if ( unlikely(cos == old_cos) )
>          {
>              spin_unlock(&info->cbm_lock);
> -            return ret;
> +            return 0;
> +        }
> +    }
> +    else
> +    {
> +        cos = pick_avail_cos(map, cos_max, old_cos);
> +        if ( cos < 0 )
> +        {
> +            spin_unlock(&info->cbm_lock);
> +            return cos;
> +        }
> +
> +        /* We try to avoid writing MSR */
> +        if ( info->cdp_enabled )
> +        {
> +            if ( map[cos].u.cdp.code == cbm_code &&
> +                 map[cos].u.cdp.data == cbm_data )
> +                need_write = 0;
> +        }
> +        else
> +            need_write = map[cos].u.cbm == cbm_code ? 0 : 1;
> +
> +        if ( need_write )
> +        {
> +            ret = write_l3_cbm(socket, cos, cbm_code, cbm_data, info->cdp_enabled);
> +            if ( ret )
> +            {
> +                spin_unlock(&info->cbm_lock);
> +                return ret;
> +            }
> +            map[cos].u.cdp.code = cbm_code;
> +            map[cos].u.cdp.data = cbm_data;
>          }
> -        found->u.cbm = cbm;
>      }
>  
> -    found->ref++;
> +    map[cos].ref++;
>      map[old_cos].ref--;
>      spin_unlock(&info->cbm_lock);
>