linux-kernel - [tip:x86/fpu] x86, xsave: Disable xsave in i387 emulation mode

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Date:	Thu, 12 Aug 2010 22:06:45 GMT
From:	tip-bot for Robert Richter <robert.richter@....com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	robert.richter@....com, tglx@...utronix.de, hpa@...ux.intel.com
Subject: [tip:x86/fpu] x86, xsave: Disable xsave in i387 emulation mode

Commit-ID:  1f999ab5a1360afc388868cc0ef9afe8edeef3be
Gitweb:     http://git.kernel.org/tip/1f999ab5a1360afc388868cc0ef9afe8edeef3be
Author:     Robert Richter <robert.richter@....com>
AuthorDate: Wed, 21 Jul 2010 19:03:57 +0200
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Thu, 12 Aug 2010 14:16:54 -0700

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>
LKML-Reference: <1279731838-1522-7-git-send-email-robert.richter@....com>
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.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 1f11f5c..2605c50 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;
 	}
--
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