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From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org
Cc: Borislav Petkov <bp@alien8.de>,
	linux-kernel@vger.kernel.org,
	Rusty Russell <rusty@rustcorp.com.au>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Rik van Riel <riel@redhat.com>, kvm list <kvm@vger.kernel.org>,
	Andy Lutomirski <luto@kernel.org>
Subject: [PATCH 2/8] fpu/bugs: Stop saving and restoring CR0.TS in fpu__init_check_bugs()
Date: Mon, 31 Oct 2016 15:18:43 -0700	[thread overview]
Message-ID: <76d1f1eacb5caead98197d1eb50ac6110ab20c6a.1477951965.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1477951965.git.luto@kernel.org>
In-Reply-To: <cover.1477951965.git.luto@kernel.org>

fpu__init_check_bugs() runs long after the early FPU init, so CR0.TS
will be clear by the time it runs.  The save-and-restore dance would
have been unnecessary anyway, though, as kernel_fpu_begin() would
have been good enough.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/kernel/fpu/bugs.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/arch/x86/kernel/fpu/bugs.c b/arch/x86/kernel/fpu/bugs.c
index aad34aafc0e0..d913047f832c 100644
--- a/arch/x86/kernel/fpu/bugs.c
+++ b/arch/x86/kernel/fpu/bugs.c
@@ -23,17 +23,12 @@ static double __initdata y = 3145727.0;
  */
 void __init fpu__init_check_bugs(void)
 {
-	u32 cr0_saved;
 	s32 fdiv_bug;
 
 	/* kernel_fpu_begin/end() relies on patched alternative instructions. */
 	if (!boot_cpu_has(X86_FEATURE_FPU))
 		return;
 
-	/* We might have CR0::TS set already, clear it: */
-	cr0_saved = read_cr0();
-	write_cr0(cr0_saved & ~X86_CR0_TS);
-
 	kernel_fpu_begin();
 
 	/*
@@ -56,8 +51,6 @@ void __init fpu__init_check_bugs(void)
 
 	kernel_fpu_end();
 
-	write_cr0(cr0_saved);
-
 	if (fdiv_bug) {
 		set_cpu_bug(&boot_cpu_data, X86_BUG_FDIV);
 		pr_warn("Hmm, FPU with FDIV bug\n");
-- 
2.7.4

  parent reply	other threads:[~2016-10-31 22:20 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-10-31 22:18 [PATCH 0/8] x86/fpu: Remove CR0.TS support Andy Lutomirski
2016-10-31 22:18 ` [PATCH 1/8] fpu/init: Get rid of two redundant clts() calls Andy Lutomirski
2016-11-01  7:13   ` [tip:x86/fpu] x86/fpu: " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` Andy Lutomirski [this message]
2016-11-01  7:14   ` [tip:x86/fpu] x86/fpu: Stop saving and restoring CR0.TS in fpu__init_check_bugs() tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 3/8] x86/fpu: Remove irq_ts_save() and irq_ts_restore() Andy Lutomirski
2016-11-01  7:14   ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 4/8] x86/kvm: Remove host CR0.TS manipulation Andy Lutomirski
2016-11-01  7:15   ` [tip:x86/fpu] x86/fpu, kvm: " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 5/8] lguest: Remove CR0.TS support Andy Lutomirski
2016-11-01  7:15   ` [tip:x86/fpu] x86/fpu, " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 6/8] x86/fpu: #NM without FPU emulation is an error Andy Lutomirski
2016-11-01  7:16   ` [tip:x86/fpu] x86/fpu: Handle #NM without FPU emulation as " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 7/8] x86/fpu: Remove stts() Andy Lutomirski
2016-11-01  7:16   ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
2016-10-31 22:18 ` [PATCH 8/8] x86/fpu: Remove clts() Andy Lutomirski
2016-11-01  7:17   ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
2016-10-31 22:41 ` [PATCH 0/8] x86/fpu: Remove CR0.TS support Paul Bolle
2016-10-31 23:04   ` Borislav Petkov
2016-10-31 23:10     ` Paul Bolle
2016-10-31 23:48       ` Borislav Petkov
2016-11-01  7:51         ` Paul Bolle
2016-11-01  8:50           ` Borislav Petkov

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