From: Ben Gras <ben@minix3.org>
Date: Wed, 28 Apr 2010 13:51:02 +0000 (+0000)
Subject: kernel: fpu_init: only enable OSXMMEXCPT in CR4 on at least SSE1 machines.
X-Git-Tag: v3.1.7~104
X-Git-Url: http://zhaoyanbai.com/repos/%22https:/www.google.com/jsapi/static/gitweb.js?a=commitdiff_plain;h=50335291ae0d647cb7f73e44d303568e7c848af0;p=minix.git

kernel: fpu_init: only enable OSXMMEXCPT in CR4 on at least SSE1 machines.

Found and debugged by totalinux at yandex.ru and Evgeniy Ivanov, thanks!
---

diff --git a/kernel/arch/i386/arch_system.c b/kernel/arch/i386/arch_system.c
index 67e19f058..934bea2a9 100644
--- a/kernel/arch/i386/arch_system.c
+++ b/kernel/arch/i386/arch_system.c
@@ -154,9 +154,15 @@ PRIVATE void fpu_init(void)
 		if(_cpufeature(_CPUF_I386_FXSR)) {
 			register struct proc *rp;
 			phys_bytes aligned_fp_area;
+			u32_t cr4 = read_cr4() | CR4_OSFXSR; /* Enable FXSR. */
 
-			/* Enable FXSR feature usage. */
-			write_cr4(read_cr4() | CR4_OSFXSR | CR4_OSXMMEXCPT);
+			/* OSXMMEXCPT if supported
+			 * FXSR feature can be available without SSE
+			 */
+			if(_cpufeature(_CPUF_I386_SSE))
+				cr4 |= CR4_OSXMMEXCPT; 
+
+			write_cr4(cr4);
 			osfxsr_feature = 1;
 
 			for (rp = BEG_PROC_ADDR; rp < END_PROC_ADDR; ++rp) {