linux-kernel - [PATCH] Fix booting pentium+ with dodgy TSC

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Message-Id: <200804061723.38766.rusty@rustcorp.com.au>
Date:	Sun, 6 Apr 2008 17:23:38 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andi Kleen <ak@...e.de>, "H. Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	lguest <lguest@...abs.org>
Subject: [PATCH] Fix booting pentium+ with dodgy TSC

Linus please apply.  Almost by definition this patch can't make things worse.

We handle a broken tsc these days, so no need to panic.  We clear the TSC bit
when tsc_init decides it's unreliable (eg. under lguest w/ bad host TSC),
leading to bogus panic.

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

diff -r 5e0a39f4d07b arch/x86/kernel/cpu/bugs.c
--- a/arch/x86/kernel/cpu/bugs.c	Sun Apr 06 13:40:39 2008 +1000
+++ b/arch/x86/kernel/cpu/bugs.c	Sun Apr 06 17:14:12 2008 +1000
@@ -143,14 +143,6 @@ static void __init check_config(void)
 #endif
 
 /*
- * If we configured ourselves for a TSC, we'd better have one!
- */
-#ifdef CONFIG_X86_TSC
-	if (!cpu_has_tsc)
-		panic("Kernel compiled for Pentium+, requires TSC feature!");
-#endif
-
-/*
  * If we were told we had a good local APIC, check for buggy Pentia,
  * i.e. all B steppings and the C2 stepping of P54C when using their
  * integrated APIC (see 11AP erratum in "Pentium Processor
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