x86/fpu: Simplify print_xstate_features()

[deliverable/linux.git] / arch / x86 / kernel / fpu / xstate.c

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index f549e2a443361f96b46bfdc4b24c4045bf4a09d9..0f849229c93bb4c218ff9b8fec2bc6db6609643b 100644 (file)
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -11,10 +11,23 @@
 #include <asm/tlbflush.h>
 #include <asm/xcr.h>
 
+static const char *xfeature_names[] =
+{
+       "x87 floating point registers"  ,
+       "SSE registers"                 ,
+       "AVX registers"                 ,
+       "MPX bounds registers"          ,
+       "MPX CSR"                       ,
+       "AVX-512 opmask"                ,
+       "AVX-512 Hi256"                 ,
+       "AVX-512 ZMM_Hi256"             ,
+       "unknown xstate feature"        ,
+};
+
 /*
  * Mask of xstate features supported by the CPU and the kernel:
  */
-u64 xfeatures_mask;
+u64 xfeatures_mask __read_mostly;
 
 /*
  * Represents init state for the supported extended state.
@@ -28,6 +41,44 @@ static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8];
 /* The number of supported xfeatures in xfeatures_mask: */
 static unsigned int xfeatures_nr;
 
+/*
+ * Return whether the system supports a given xfeature.
+ *
+ * Also return the name of the (most advanced) feature that the caller requested:
+ */
+int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name)
+{
+       u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask;
+
+       if (unlikely(feature_name)) {
+               long xfeature_idx, max_idx;
+               u64 xfeatures_print;
+               /*
+                * So we use FLS here to be able to print the most advanced
+                * feature that was requested but is missing. So if a driver
+                * asks about "XSTATE_SSE | XSTATE_YMM" we'll print the
+                * missing AVX feature - this is the most informative message
+                * to users:
+                */
+               if (xfeatures_missing)
+                       xfeatures_print = xfeatures_missing;
+               else
+                       xfeatures_print = xfeatures_needed;
+
+               xfeature_idx = fls64(xfeatures_print)-1;
+               max_idx = ARRAY_SIZE(xfeature_names)-1;
+               xfeature_idx = min(xfeature_idx, max_idx);
+
+               *feature_name = xfeature_names[xfeature_idx];
+       }
+
+       if (xfeatures_missing)
+               return 0;
+
+       return 1;
+}
+EXPORT_SYMBOL_GPL(cpu_has_xfeatures);
+
 /*
  * When executing XSAVEOPT (optimized XSAVE), if a processor implementation
  * detects that an FPU state component is still (or is again) in its
@@ -494,13 +545,12 @@ static void __init setup_xstate_features(void)
        } while (1);
 }
 
-static void print_xstate_feature(u64 xstate_mask, const char *desc)
+static void print_xstate_feature(u64 xstate_mask)
 {
-       if (xfeatures_mask & xstate_mask) {
-               int xstate_feature = fls64(xstate_mask)-1;
+       const char *feature_name;
 
-               pr_info("x86/fpu: Supporting XSAVE feature %2d: '%s'\n", xstate_feature, desc);
-       }
+       if (cpu_has_xfeatures(xstate_mask, &feature_name))
+               pr_info("x86/fpu: Supporting XSAVE feature 0x%02Lx: '%s'\n", xstate_mask, feature_name);
 }
 
 /*
@@ -508,14 +558,14 @@ static void print_xstate_feature(u64 xstate_mask, const char *desc)
  */
 static void print_xstate_features(void)
 {
-       print_xstate_feature(XSTATE_FP,         "x87 floating point registers");
-       print_xstate_feature(XSTATE_SSE,        "SSE registers");
-       print_xstate_feature(XSTATE_YMM,        "AVX registers");
-       print_xstate_feature(XSTATE_BNDREGS,    "MPX bounds registers");
-       print_xstate_feature(XSTATE_BNDCSR,     "MPX CSR");
-       print_xstate_feature(XSTATE_OPMASK,     "AVX-512 opmask");
-       print_xstate_feature(XSTATE_ZMM_Hi256,  "AVX-512 Hi256");
-       print_xstate_feature(XSTATE_Hi16_ZMM,   "AVX-512 ZMM_Hi256");
+       print_xstate_feature(XSTATE_FP);
+       print_xstate_feature(XSTATE_SSE);
+       print_xstate_feature(XSTATE_YMM);
+       print_xstate_feature(XSTATE_BNDREGS);
+       print_xstate_feature(XSTATE_BNDCSR);
+       print_xstate_feature(XSTATE_OPMASK);
+       print_xstate_feature(XSTATE_ZMM_Hi256);
+       print_xstate_feature(XSTATE_Hi16_ZMM);
 }
 
 /*