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* [PATCH 1/4] powerpc/tm: Add commandline option to disable hardware transactional memory
@ 2017-10-12 10:17 Michael Ellerman
  2017-10-12 10:17 ` [PATCH 2/4] powerpc: Add PPC_FEATURE2_HTM_NO_SUSPEND Michael Ellerman
                   ` (5 more replies)
  0 siblings, 6 replies; 24+ messages in thread
From: Michael Ellerman @ 2017-10-12 10:17 UTC (permalink / raw)
  To: linuxppc-dev; +Cc: mikey, benh, stewart, cyrilbur

From: Cyril Bur <cyrilbur@gmail.com>

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 ++++
 arch/powerpc/kernel/prom.c                      | 31 +++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 05496622b4ef..ef03e6e16bdb 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -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
 
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index f83056297441..d9bd6555f980 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -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");
 }
 
-- 
2.7.4

^ permalink raw reply related	[flat|nested] 24+ messages in thread
end of thread, other threads:[~2017-10-24  8:12 UTC | newest]

Thread overview: 24+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2017-10-12 10:17 [PATCH 1/4] powerpc/tm: Add commandline option to disable hardware transactional memory Michael Ellerman
2017-10-12 10:17 ` [PATCH 2/4] powerpc: Add PPC_FEATURE2_HTM_NO_SUSPEND Michael Ellerman
2017-10-12 10:17 ` [PATCH 3/4] powerpc/powernv: Enable TM without suspend if possible Michael Ellerman
2017-10-19 10:07   ` Florian Weimer
2017-10-19 12:04     ` Tulio Magno Quites Machado Filho
2017-10-19 12:45       ` Florian Weimer
2017-10-19 13:34     ` Tulio Magno Quites Machado Filho
2017-10-19 15:13       ` Adhemerval Zanella
2017-10-22  9:59         ` Michael Ellerman
2017-10-20  2:47       ` Michael Neuling
2017-10-22  9:48       ` Michael Ellerman
2017-10-22  9:54     ` Michael Ellerman
2017-10-12 10:17 ` [PATCH 4/4] powerpc/tm: P9 disable transactionally suspended sigcontexts Michael Ellerman
2017-10-12 11:58 ` [PATCH 5/4] KVM: PPC: Tie KVM_CAP_PPC_HTM to the user-visible TM feature Michael Ellerman
2017-10-24  8:08   ` [5/4] " Michael Ellerman
2017-10-20 11:45 ` [PATCH 1/4] powerpc/tm: Add commandline option to disable hardware transactional memory Breno Leitao
2017-10-20 12:58   ` David Laight
2017-10-21  1:00     ` Michael Neuling
2017-10-23  9:01       ` David Laight
2017-10-23  9:15         ` Michael Neuling
2017-10-21  0:58   ` Michael Neuling
2017-10-23 12:56     ` Breno Leitao
2017-10-24  8:12       ` Michael Ellerman
2017-10-24  8:08 ` [1/4] " Michael Ellerman

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