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[RFC,11/12,WIP] powerpc/tm: Afterthoughts

Message ID 20180220002241.29648-12-cyrilbur@gmail.com (mailing list archive)
State Superseded, archived
Headers show
Series Deal with TM on kernel entry and exit | expand

Commit Message

Cyril Bur Feb. 20, 2018, 12:22 a.m. UTC 
---
 arch/powerpc/kernel/process.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)
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Patch

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 674f75c56172..6ce41ee62b24 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1079,6 +1079,12 @@  static inline void __switch_to_tm(struct task_struct *prev,
 		if (!MSR_TM_ACTIVE(prev->thread.regs->msr) && prev->thread.load_tm == 0)
 			prev->thread.regs->msr &= ~MSR_TM;
 	}
+
+	/*
+	 * Now that we're reclaiming on kernel entry, we should never
+	 * get here still with user checkpointed state on the CPU
+	 */
+	BUG_ON(MSR_TM_ACTIVE(mfmsr()));
 }
 
 /*
@@ -1326,7 +1332,17 @@  struct task_struct *__switch_to(struct task_struct *prev,
 	}
 
 	if (current_thread_info()->task->thread.regs) {
-		restore_math(current_thread_info()->task->thread.regs);
+		/*
+		 * Calling this now has reloaded the live state, which
+		 * gets overwritten with the checkpointed state right
+		 * before the trecheckpoint. BUT the MSR still has
+		 * that the live state is on the CPU, which it isn't.
+		 *
+		 * restore_math(current_thread_info()->task->thread.regs);
+		 * Therefore:
+		 */
+		if (!MSR_TM_ACTIVE(current_thread_info()->task->thread.regs->msr))
+			restore_math(current_thread_info()->task->thread.regs);
 
 		/*
 		 * The copy-paste buffer can only store into foreign real