powerpc/tm: Add commandline option to disable hardware transactional memory (07fd1761) · Commits · 戴 / test

Currently the kernel relies on firmware to inform it whether or not the CPU supports HTM and as long as the kernel was built with CONFIG_PPC_TRANSACTIONAL_MEM=y then it will allow userspace to make use of the facility. There may be situations where it would be advantageous for the kernel to not allow userspace to use HTM, currently the only way to achieve this is to recompile the kernel with CONFIG_PPC_TRANSACTIONAL_MEM=n. This patch adds a simple commandline option so that HTM can be disabled at boot time. Signed-off-by:

Cyril Bur <cyrilbur@gmail.com> [mpe: Simplify to a bool, move to prom.c, put doco in the right place. Always disable, regardless of initial state, to avoid user confusion.] Signed-off-by:

Michael Ellerman <mpe@ellerman.id.au>

Documentation/admin-guide/kernel-parameters.txt

+4 −0

Original line number	Diff line number	Diff line
		@@ -3185,6 +3185,10 @@
		allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
		There is some performance impact when enabling this.

		ppc_tm= [PPC]
		Format: {"off"}
		Disable Hardware Transactional Memory

		print-fatal-signals=
		[KNL] debug: print fatal signals

arch/powerpc/kernel/prom.c

+31 −0

Original line number	Diff line number	Diff line
		@@ -658,6 +658,35 @@ static void __init early_reserve_mem(void)
		#endif
		}

		#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
		static bool tm_disabled __initdata;

		static int __init parse_ppc_tm(char *str)
		{
		bool res;

		if (kstrtobool(str, &res))
		return -EINVAL;

		tm_disabled = !res;

		return 0;
		}
		early_param("ppc_tm", parse_ppc_tm);

		static void __init tm_init(void)
		{
		if (tm_disabled) {
		pr_info("Disabling hardware transactional memory (HTM)\n");
		cur_cpu_spec->cpu_user_features2 &=
		~(PPC_FEATURE2_HTM_NOSC \| PPC_FEATURE2_HTM);
		cur_cpu_spec->cpu_features &= ~CPU_FTR_TM;
		}
		}
		#else
		static void tm_init(void) { }
		#endif /* CONFIG_PPC_TRANSACTIONAL_MEM */

		void __init early_init_devtree(void *params)
		{
		phys_addr_t limit;
		@@ -767,6 +796,8 @@ void __init early_init_devtree(void *params)
		powerpc_firmware_features \|= FW_FEATURE_PS3_POSSIBLE;
		#endif

		tm_init();

		DBG(" <- early_init_devtree()\n");
		}

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