Expose XSAVES in /proc/cpuinfo

Linux started doing this in b8be15d588060a03569ac85dc4a0247460988f5b
("x86/fpu/xstate: Re-enable XSAVES"), which first appeared in 4.8.

PiperOrigin-RevId: 233800931
Change-Id: Icac2c2b03ccf1a91f3070431efb5152ca619fca3

pkg/cpuid/cpuid.go

@@ -361,6 +361,7 @@ var x86FeatureStrings = map[Feature]string{
 	X86FeatureXSAVEOPT: "xsaveopt",
 	X86FeatureXSAVEC:   "xsavec",
 	X86FeatureXGETBV1:  "xgetbv1",
+	X86FeatureXSAVES:   "xsaves",
 
 	// Block 5.
 	X86FeatureLAHF64:       "lahf_lm", // LAHF/SAHF in long mode
@@ -415,9 +416,6 @@ var x86FeatureParseOnlyStrings = map[Feature]string{
 
 	// Block 3.
 	X86FeaturePREFETCHWT1: "prefetchwt1",
-
-	// Block 4.
-	X86FeatureXSAVES: "xsaves",
 }
 
 // Just a way to wrap cpuid function numbers.

pkg/cpuid/cpuid_parse_test.go

@@ -114,6 +114,11 @@ func TestHostFeatureFlags(t *testing.T) {
 			// PKU only exposed in dfb4a70f20c5b3880da56ee4c9484bdb4e8f1e65
 			// (4.9).
 			continue
+		// Block 4.
+		case f == X86FeatureXSAVES && (major < 4 || major == 4 && minor < 8):
+			// XSAVES only exposed in
+			// b8be15d588060a03569ac85dc4a0247460988f5b (4.8).
+			continue
 		}
 
 		hidden := f.flagString(true) == ""