x86, cpu: Add forcepae parameter for booting PAE kernels on PAE-disabled Pentium M (69f2366c) · Commits · 戴 / test

Documentation/kernel-parameters.txt

+7 −0

Original line number	Diff line number	Diff line
		@@ -1011,6 +1011,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
		parameter will force ia64_sal_cache_flush to call
		ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.

		forcepae [X86-32]
		Forcefully enable Physical Address Extension (PAE).
		Many Pentium M systems disable PAE but may have a
		functionally usable PAE implementation.
		Warning: use of this parameter will taint the kernel
		and may cause unknown problems.

		ftrace=[tracer]
		[FTRACE] will set and start the specified tracer
		as early as possible in order to facilitate early

+20 −0

Original line number	Diff line number	Diff line
		@@ -67,6 +67,13 @@ static int is_transmeta(void)
		cpu_vendor[2] == A32('M', 'x', '8', '6');
		}

		static int is_intel(void)
		{
		return cpu_vendor[0] == A32('G', 'e', 'n', 'u') &&
		cpu_vendor[1] == A32('i', 'n', 'e', 'I') &&
		cpu_vendor[2] == A32('n', 't', 'e', 'l');
		}

		/* Returns a bitmask of which words we have error bits in */
		static int check_cpuflags(void)
		{
		@@ -153,6 +160,19 @@ int check_cpu(int cpu_level_ptr, int req_level_ptr, u32 **err_flags_ptr)
		asm("wrmsr" : : "a" (eax), "d" (edx), "c" (ecx));

		err = check_cpuflags();
		} else if (err == 0x01 &&
		!(err_flags[0] & ~(1 << X86_FEATURE_PAE)) &&
		is_intel() && cpu.level == 6 &&
		(cpu.model == 9 \|\| cpu.model == 13)) {
		/* PAE is disabled on this Pentium M but can be forced */
		if (cmdline_find_option_bool("forcepae")) {
		puts("WARNING: Forcing PAE in CPU flags\n");
		set_bit(X86_FEATURE_PAE, cpu.flags);
		err = check_cpuflags();
		}
		else {
		puts("WARNING: PAE disabled. Use parameter 'forcepae' to enable at your own risk!\n");
		}
		}

		if (err_flags_ptr)

+19 −0

Original line number	Diff line number	Diff line
		@@ -186,6 +186,14 @@ static void intel_smp_check(struct cpuinfo_x86 *c)
		}
		}

		static int forcepae;
		static int __init forcepae_setup(char *__unused)
		{
		forcepae = 1;
		return 1;
		}
		__setup("forcepae", forcepae_setup);

		static void intel_workarounds(struct cpuinfo_x86 *c)
		{
		#ifdef CONFIG_X86_F00F_BUG
		@@ -213,6 +221,17 @@ static void intel_workarounds(struct cpuinfo_x86 *c)
		if ((c->x86<<8 \| c->x86_model<<4 \| c->x86_mask) < 0x633)
		clear_cpu_cap(c, X86_FEATURE_SEP);

		/*
		* PAE CPUID issue: many Pentium M report no PAE but may have a
		* functionally usable PAE implementation.
		* Forcefully enable PAE if kernel parameter "forcepae" is present.
		*/
		if (forcepae) {
		printk(KERN_WARNING "PAE forced!\n");
		set_cpu_cap(c, X86_FEATURE_PAE);
		add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_NOW_UNRELIABLE);
		}

		/*
		* P4 Xeon errata 037 workaround.
		* Hardware prefetcher may cause stale data to be loaded into the cache.