Revert "powerpc/tm: Abort syscalls in active transactions"

This reverts commit feba40362b.

Although the principle of this change is good, the implementation has a
few issues.

Firstly we can sometimes fail to abort a syscall because r12 may have
been clobbered by C code if we went down the virtual CPU accounting
path, or if syscall tracing was enabled.

Secondly we have decided that it is safer to abort the syscall even
earlier in the syscall entry path, so that we avoid the syscall tracing
path when we are transactional.

So that we have time to thoroughly test those changes we have decided to
revert this for this merge window and will merge the fixed version in
the next window.

NB. Rather than reverting the selftest we just drop tm-syscall from
TEST_PROGS so that it's not run by default.

Fixes: feba40362b ("powerpc/tm: Abort syscalls in active transactions")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/entry_64.S

@@ -34,7 +34,6 @@
 #include <asm/ftrace.h>
 #include <asm/hw_irq.h>
 #include <asm/context_tracking.h>
-#include <asm/tm.h>
 
 /*
  * System calls.
@@ -146,24 +145,6 @@ END_FW_FTR_SECTION_IFSET(FW_FEATURE_SPLPAR)
 	andi.	r11,r10,_TIF_SYSCALL_DOTRACE
 	bne	syscall_dotrace
 .Lsyscall_dotrace_cont:
-#ifdef CONFIG_PPC_TRANSACTIONAL_MEM
-BEGIN_FTR_SECTION
-	b	1f
-END_FTR_SECTION_IFCLR(CPU_FTR_TM)
-	extrdi.	r11, r12, 1, (63-MSR_TS_T_LG) /* transaction active? */
-	beq+	1f
-
-	/* Doom the transaction and don't perform the syscall: */
-	mfmsr	r11
-	li	r12, 1
-	rldimi	r11, r12, MSR_TM_LG, 63-MSR_TM_LG
-	mtmsrd	r11, 0
-	li	r11, (TM_CAUSE_SYSCALL|TM_CAUSE_PERSISTENT)
-	TABORT(R11)
-
-	b	.Lsyscall_exit
-1:
-#endif
 	cmpldi	0,r0,NR_syscalls
 	bge-	syscall_enosys