[PATCH 4.20 41/65] Revert "powerpc/tm: Unset MSR[TS] if not recheckpointing"

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

This reverts commit d412deb85a4aada382352a8202beb7af8921cd53 which is
commit 6f5b9f018f4c7686fd944d920209d1382d320e4e upstream.

It breaks the powerpc build, so drop it from the tree until a fix goes
upstream.

Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: Breno Leitao <leitao@xxxxxxxxxx>
Cc: Michal Suchánek <msuchanek@xxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Christoph Biedl <linux-kernel.bfrz@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/powerpc/kernel/signal_32.c |   18 +++++-------------
 arch/powerpc/kernel/signal_64.c |   20 ++++----------------
 2 files changed, 9 insertions(+), 29 deletions(-)

--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -1140,11 +1140,11 @@ SYSCALL_DEFINE0(rt_sigreturn)
 {
 	struct rt_sigframe __user *rt_sf;
 	struct pt_regs *regs = current_pt_regs();
-	int tm_restore = 0;
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 	struct ucontext __user *uc_transact;
 	unsigned long msr_hi;
 	unsigned long tmp;
+	int tm_restore = 0;
 #endif
 	/* Always make any pending restarted system calls return -EINTR */
 	current->restart_block.fn = do_no_restart_syscall;
@@ -1192,19 +1192,11 @@ SYSCALL_DEFINE0(rt_sigreturn)
 				goto bad;
 		}
 	}
-	if (!tm_restore) {
-		/*
-		 * Unset regs->msr because ucontext MSR TS is not
-		 * set, and recheckpoint was not called. This avoid
-		 * hitting a TM Bad thing at RFID
-		 */
-		regs->msr &= ~MSR_TS_MASK;
-	}
-	/* Fall through, for non-TM restore */
-#endif
 	if (!tm_restore)
-		if (do_setcontext(&rt_sf->uc, regs, 1))
-			goto bad;
+		/* Fall through, for non-TM restore */
+#endif
+	if (do_setcontext(&rt_sf->uc, regs, 1))
+		goto bad;
 
 	/*
 	 * It's not clear whether or why it is desirable to save the
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -740,23 +740,11 @@ SYSCALL_DEFINE0(rt_sigreturn)
 					   &uc_transact->uc_mcontext))
 			goto badframe;
 	}
-#endif
+	else
 	/* Fall through, for non-TM restore */
-	if (!MSR_TM_ACTIVE(msr)) {
-		/*
-		 * Unset MSR[TS] on the thread regs since MSR from user
-		 * context does not have MSR active, and recheckpoint was
-		 * not called since restore_tm_sigcontexts() was not called
-		 * also.
-		 *
-		 * If not unsetting it, the code can RFID to userspace with
-		 * MSR[TS] set, but without CPU in the proper state,
-		 * causing a TM bad thing.
-		 */
-		current->thread.regs->msr &= ~MSR_TS_MASK;
-		if (restore_sigcontext(current, NULL, 1, &uc->uc_mcontext))
-			goto badframe;
-	}
+#endif
+	if (restore_sigcontext(current, NULL, 1, &uc->uc_mcontext))
+		goto badframe;
 
 	if (restore_altstack(&uc->uc_stack))
 		goto badframe;