[Xen-devel] [PATCH v10 12/25] x86: refactor psr: L3 CAT: set value: implement cos id picking flow.

[Yi Sun <yi.y.sun@xxxxxxxxxxxxxxx>]

Continue from previous patch:
'x86: refactor psr: L3 CAT: set value: implement cos finding flow.'

If fail to find a COS ID, we need pick a new COS ID for domain. Only COS ID
that ref[COS_ID] is 1 or 0 can be picked to input a new set feature values.

Signed-off-by: Yi Sun <yi.y.sun@xxxxxxxxxxxxxxx>
---
v10:
    - remove 'fits_cos_max' hook and CAT implementation. Move the process into
      generic flow.
      (suggested by Jan Beulich)
    - changes about 'props'.
      (suggested by Jan Beulich)
    - adjust codes positions.
      (suggested by Jan Beulich)
v9:
    - modify return value of 'pick_avail_cos' to make it more accurate.
    - rename 'l3_cat_fits_cos_max' to 'cat_fits_cos_max' to cover L3/L2 CAT
      features.
      (suggested by Roger Pau)
    - replace feature list handling to feature array handling.
      (suggested by Roger Pau)
    - fix comment.
      (suggested by Wei Liu)
    - directly use 'cos_reg_val[0]' as default value.
      (suggested by Jan Beulich)
    - replace 'get_cos_num' to 'feat->cos_num'.
      (suggested by Jan Beulich)
    - modify patch title to indicate 'L3 CAT'.
      (suggested by Jan Beulich)
    - changes about 'uint64_t' to 'uint32_t'.
      (suggested by Jan Beulich)
v5:
    - modify commit message to provide exact patch name to continue from.
      (suggested by Jan Beulich)
    - change 'exceeds_cos_max' to 'fits_cos_max' to be accurate.
      (suggested by Jan Beulich)
    - modify comments according to changes of codes.
      (suggested by Jan Beulich)
    - modify return value of callback functions because we do not need them
      to return number of entries the feature uses. In caller, we call
      'get_cos_num' to get the number of entries the feature uses.
      (suggested by Jan Beulich)
    - move type check out from callback functions to caller.
      (suggested by Jan Beulich)
    - modify variables names to make them better, e.g. 'feat_tmp' to 'feat'.
      (suggested by Jan Beulich)
    - modify code format.
      (suggested by Jan Beulich)
v4:
    - create this patch to make codes easier to understand.
      (suggested by Jan Beulich)
---
 xen/arch/x86/psr.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 68 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/psr.c b/xen/arch/x86/psr.c
index a6c6f18..44c9313 100644
--- a/xen/arch/x86/psr.c
+++ b/xen/arch/x86/psr.c
@@ -800,15 +800,82 @@ static int find_cos(const uint32_t val[], unsigned int 
array_len,
     return -ENOENT;
 }
 
+static bool fits_cos_max(const uint32_t val[],
+                         uint32_t array_len,
+                         const struct psr_socket_info *info,
+                         unsigned int cos)
+{
+    unsigned int i;
+
+    for ( i = 0; i < PSR_SOCKET_MAX_FEAT; i++ )
+    {
+        uint32_t default_val = 0;
+        const struct feat_node *feat = info->features[i];
+        if ( !feat )
+            continue;
+
+        if ( array_len < feat->props->cos_num )
+            return false;
+
+        if ( cos > feat->props->cos_max )
+        {
+            feat->props->get_val(feat, 0, &default_val);
+            if ( val[0] != default_val )
+                return false;
+        }
+
+        array_len -= feat->props->cos_num;
+
+        val += feat->props->cos_num;
+    }
+
+    return true;
+}
+
 static int pick_avail_cos(const struct psr_socket_info *info,
                           spinlock_t *ref_lock,
                           const uint32_t val[], unsigned int array_len,
                           unsigned int old_cos,
                           enum psr_feat_type feat_type)
 {
+    unsigned int cos;
+    unsigned int cos_max = 0;
+    const struct feat_node *feat;
+    const unsigned int *ref = info->cos_ref;
+
     ASSERT(spin_is_locked(ref_lock));
 
-    return -ENOENT;
+    /* cos_max is the one of the feature which is being set. */
+    feat = info->features[feat_type];
+    if ( !feat )
+        return -ENOENT;
+
+    cos_max = feat->props->cos_max;
+    if ( !cos_max )
+        return -ENOENT;
+
+    /* We cannot use id 0 because it stores the default values. */
+    if ( old_cos && ref[old_cos] == 1 &&
+         fits_cos_max(val, array_len, info, old_cos) )
+            return old_cos;
+
+    /* Find an unused one other than cos0. */
+    for ( cos = 1; cos <= cos_max; cos++ )
+    {
+        /*
+         * ref is 0 means this COS is not used by other domain and
+         * can be used for current setting.
+         */
+        if ( !ref[cos] )
+        {
+            if ( !fits_cos_max(val, array_len, info, cos) )
+                break;
+
+            return cos;
+        }
+    }
+
+    return -EOVERFLOW;
 }
 
 static int write_psr_msr(unsigned int socket, unsigned int cos,
-- 
1.9.1


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