linux-kernel - [ 174/262] x86, avx: dont use avx instructions with "noxsave" boot param

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Date:	Fri, 28 Sep 2012 11:51:43 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg KH <gregkh@...uxfoundation.org>, alan@...rguk.ukuu.org.uk,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [ 174/262] x86, avx: dont use avx instructions with "noxsave" boot param

From: Greg KH <gregkh@...uxfoundation.org>

3.5-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Suresh Siddha <suresh.b.siddha@...el.com>

commit c6fd893da927c6cefb2ece22402765379921a834 upstream.

Clear AVX, AVX2 features along with clearing XSAVE feature bits,
as part of the parsing "noxsave" parameter.

Fixes the kernel boot panic with "noxsave" boot parameter.

We could have checked cpu_has_osxsave along with cpu_has_avx etc, but Peter
mentioned clearing the feature bits will be better for uses like
static_cpu_has() etc.

Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
Link: http://lkml.kernel.org/r/1343755754.2041.2.camel@sbsiddha-desk.sc.intel.com
Signed-off-by: H. Peter Anvin <hpa@...or.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/cpu/common.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -144,6 +144,8 @@ static int __init x86_xsave_setup(char *
 {
 	setup_clear_cpu_cap(X86_FEATURE_XSAVE);
 	setup_clear_cpu_cap(X86_FEATURE_XSAVEOPT);
+	setup_clear_cpu_cap(X86_FEATURE_AVX);
+	setup_clear_cpu_cap(X86_FEATURE_AVX2);
 	return 1;
 }
 __setup("noxsave", x86_xsave_setup);

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