linux-kernel - [PATCH 6/7] x86, xsave: disable xsave in i387 emulation mode

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Date:	Wed, 21 Jul 2010 19:03:57 +0200
From:	Robert Richter <robert.richter@....com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Robert Richter <robert.richter@....com>
Subject: [PATCH 6/7] x86, xsave: disable xsave in i387 emulation mode

xsave is broken for (!HAVE_HWFP). This is the case if config
MATH_EMULATION is enabled, 'no387' kernel parameter is set and xsave
exists. xsave will not work because x86/math-emu and xsave share the
same memory. As this case can be treated as corner case we simply
disable xsave then.

Signed-off-by: Robert Richter <robert.richter@....com>
---
 arch/x86/kernel/i387.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index e73c54e..ff81143 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -67,6 +67,12 @@ static void __cpuinit init_thread_xstate(void)
 	 */
 
 	if (!HAVE_HWFP) {
+		/*
+		 * Disable xsave as we do not support it if i387
+		 * emulation is enabled.
+		 */
+		setup_clear_cpu_cap(X86_FEATURE_XSAVE);
+		setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
 		xstate_size = sizeof(struct i387_soft_struct);
 		return;
 	}
-- 
1.7.1.1


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