xf86-video-intel: src/sna/sna_cpu.c

[Chris Wilson]

 src/sna/sna_cpu.c |   17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

New commits:
commit 0b479504c82bd81c0b93de0e6529eae928eea3bf
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Tue Mar 26 16:12:30 2013 +0000

    sna: Check for OS support of AVX/AVX2 before use
    
    If the OS has not initialised support for the extended instructions,
    then their use may result in general protection faults.
    
    Based on code by Thiago Macieira.
    
    Reported-by: Arjan van de Ven <arjan at linux.intel.com>
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

diff --git a/src/sna/sna_cpu.c b/src/sna/sna_cpu.c
index ab4942b..ff83ba5 100644
--- a/src/sna/sna_cpu.c
+++ b/src/sna/sna_cpu.c
@@ -39,11 +39,17 @@
 #define bit_AVX2 (1<<5)
 #endif
 
+#define xgetbv(index,eax,edx)                                   \
+	__asm__ ("xgetbv" : "=a"(eax), "=d"(edx) : "c" (index))
+
+#define has_YMM 0x1
+
 unsigned sna_cpu_detect(void)
 {
 	unsigned max = __get_cpuid_max(false, 0);
 	unsigned int eax, ebx, ecx, edx;
 	unsigned features = 0;
+	unsigned extra = 0;
 
 	if (max >= 1) {
 		__cpuid(1, eax, ebx, ecx, edx);
@@ -59,7 +65,14 @@ unsigned sna_cpu_detect(void)
 		if (ecx & bit_SSE4_2)
 			features |= SSE4_2;
 
-		if (ecx & bit_AVX)
+		if (ecx & bit_OSXSAVE) {
+			unsigned int bv_eax, bv_ecx;
+			xgetbv(0, bv_eax, bv_ecx);
+			if ((bv_eax & 6) == 6)
+				extra |= has_YMM;
+		}
+
+		if (extra & has_YMM && ecx & bit_AVX)
 			features |= AVX;
 
 		if (edx & bit_MMX)
@@ -74,7 +87,7 @@ unsigned sna_cpu_detect(void)
 
 	if (max >= 7) {
 		__cpuid_count(7, 0, eax, ebx, ecx, edx);
-		if (ebx & bit_AVX2)
+		if (extra & has_YMM && ebx & bit_AVX2)
 			features |= AVX2;
 	}