[Xen-devel] [PATCH v6 04/16] x86: a few optimizations to psr codes

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

This patch refines psr codes:
1. Change type of 'cat_init_feature' to 'bool' to remove the pointless
   returning of error code.
2. Move printk in 'cat_init_feature' to reduce a return path.
3. Define a local variable 'feat_mask' in 'psr_cpu_init' to reduce calling of
   'cpuid_count_leaf()'.

Signed-off-by: Yi Sun <yi.y.sun@xxxxxxxxxxxxxxx>
Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>

v6:
    - restore 'write_msr()' type to 'void'.
      (suggested by Jan Beulich and Roger Pau Monné)
    - change 'ebx' in 'psr_cpu_init' to 'feat_mask'.
      (suggested by Jan Beulich and Roger Pau Monné)
v5:
    - create this patch to make codes clearer.
      (suggested by Jan Beulich and Roger Pau Monné)
---
 xen/arch/x86/psr.c | 35 +++++++++++++++++------------------
 1 file changed, 17 insertions(+), 18 deletions(-)

diff --git a/xen/arch/x86/psr.c b/xen/arch/x86/psr.c
index 263ddbe..5945efa 100644
--- a/xen/arch/x86/psr.c
+++ b/xen/arch/x86/psr.c
@@ -273,10 +273,10 @@ static bool psr_check_cbm(unsigned int cbm_len, unsigned 
long cbm)
 }
 
 /* CAT common functions implementation. */
-static int cat_init_feature(const struct cpuid_leaf *regs,
-                            struct feat_node *feat,
-                            struct psr_socket_info *info,
-                            enum psr_feat_type type)
+static bool cat_init_feature(const struct cpuid_leaf *regs,
+                             struct feat_node *feat,
+                             struct psr_socket_info *info,
+                             enum psr_feat_type type)
 {
     const char *const cat_feat_name[FEAT_TYPE_NUM] = {
         [FEAT_TYPE_L3_CAT] = "L3 CAT",
@@ -286,7 +286,7 @@ static int cat_init_feature(const struct cpuid_leaf *regs,
 
     /* No valid value so do not enable feature. */
     if ( !regs->a || !regs->d )
-        return -ENOENT;
+        return false;
 
     feat->cbm_len = (regs->a & CAT_CBM_LEN_MASK) + 1;
     feat->cos_max = min(opt_cos_max, regs->d & CAT_COS_MAX_MASK);
@@ -296,7 +296,7 @@ static int cat_init_feature(const struct cpuid_leaf *regs,
     case FEAT_TYPE_L3_CAT:
     case FEAT_TYPE_L2_CAT:
         if ( feat->cos_max < 1 )
-            return -ENOENT;
+            return false;
 
         /* We reserve cos=0 as default cbm (all bits within cbm_len are 1). */
         feat->cos_reg_val[0] = cat_default_val(feat->cbm_len);
@@ -313,7 +313,7 @@ static int cat_init_feature(const struct cpuid_leaf *regs,
         uint64_t val;
 
         if ( feat->cos_max < 3 )
-            return -ENOENT;
+            return false;
 
         /* Cut half of cos_max when CDP is enabled. */
         feat->cos_max = (feat->cos_max - 1) >> 1;
@@ -332,20 +332,18 @@ static int cat_init_feature(const struct cpuid_leaf *regs,
     }
 
     default:
-        return -ENOENT;
+        return false;
     }
 
     /* Add this feature into array. */
     info->features[type] = feat;
 
-    if ( !opt_cpu_info )
-        return 0;
-
-    printk(XENLOG_INFO "%s: enabled on socket %u, cos_max:%u, cbm_len:%u\n",
-           cat_feat_name[type], cpu_to_socket(smp_processor_id()),
-           feat->cos_max, feat->cbm_len);
+    if ( opt_cpu_info )
+        printk(XENLOG_INFO "%s: enabled on socket %u, cos_max:%u, 
cbm_len:%u\n",
+               cat_feat_name[type], cpu_to_socket(smp_processor_id()),
+               feat->cos_max, feat->cbm_len);
 
-    return 0;
+    return true;
 }
 
 static bool cat_get_feat_info(const struct feat_node *feat,
@@ -1416,6 +1414,7 @@ static void psr_cpu_init(void)
     unsigned int socket, cpu = smp_processor_id();
     struct feat_node *feat;
     struct cpuid_leaf regs;
+    uint32_t feat_mask;
 
     if ( !psr_alloc_feat_enabled() || !boot_cpu_has(X86_FEATURE_PQE) )
         goto assoc_init;
@@ -1434,7 +1433,8 @@ static void psr_cpu_init(void)
     spin_lock_init(&info->ref_lock);
 
     cpuid_count_leaf(PSR_CPUID_LEVEL_CAT, 0, &regs);
-    if ( regs.b & PSR_RESOURCE_TYPE_L3 )
+    feat_mask = regs.b;
+    if ( feat_mask & PSR_RESOURCE_TYPE_L3 )
     {
         cpuid_count_leaf(PSR_CPUID_LEVEL_CAT, 1, &regs);
 
@@ -1455,8 +1455,7 @@ static void psr_cpu_init(void)
         }
     }
 
-    cpuid_count_leaf(PSR_CPUID_LEVEL_CAT, 0, &regs);
-    if ( regs.b & PSR_RESOURCE_TYPE_L2 )
+    if ( feat_mask & PSR_RESOURCE_TYPE_L2 )
     {
         cpuid_count_leaf(PSR_CPUID_LEVEL_CAT, 2, &regs);
 
-- 
1.9.1


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