parisc: Simplify fast path for non-access data TLB faults

Commit Message

John David Anglin March 9, 2022, 9:23 p.m. UTC

With the latest cache fix for non-access faults and the support for
non-access faults (code 17) in handle_interruption, we can remove
the fast path emulation for fdc, fic, pdc, lpa, probe and probei
instructions.

Signed-off-by: John David Anglin <[e-mail]>
---

Patch

diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S
index 6e9cdb269862..ecf50159359e 100644
--- a/arch/parisc/kernel/entry.S
+++ b/arch/parisc/kernel/entry.S
@@ -1288,74 +1288,12 @@  nadtlb_check_alias_20:
 nadtlb_emulate:
 
 	/*
-	 * Non access misses can be caused by fdc,fic,pdc,lpa,probe and
-	 * probei instructions. We don't want to fault for these
-	 * instructions (not only does it not make sense, it can cause
-	 * deadlocks, since some flushes are done with the mmap
-	 * semaphore held). If the translation doesn't exist, we can't
-	 * insert a translation, so have to emulate the side effects
-	 * of the instruction. Since we don't insert a translation
-	 * we can get a lot of faults during a flush loop, so it makes
-	 * sense to try to do it here with minimum overhead. We only
-	 * emulate fdc,fic,pdc,probew,prober instructions whose base 
-	 * and index registers are not shadowed. We defer everything 
-	 * else to the "slow" path.
+	 * Non-access misses can be caused by fdc,fic,pdc,lpa,probe and
+	 * probei instructions. The kernel no longer faults doing flushes.
+	 * Use of lpa and probe instructions is rare. Given the issue
+	 * with shadow registers, we defer everything to the "slow" path.
 	 */
-
-	mfctl           %cr19,%r9 /* Get iir */
-
-	/* PA 2.0 Arch Ref. Book pg 382 has a good description of the insn bits.
-	   Checks for fdc,fdce,pdc,"fic,4f",prober,probeir,probew, probeiw */
-
-	/* Checks for fdc,fdce,pdc,"fic,4f" only */
-	ldi             0x280,%r16
-	and             %r9,%r16,%r17
-	cmpb,<>,n       %r16,%r17,nadtlb_probe_check
-	bb,>=,n         %r9,26,nadtlb_nullify  /* m bit not set, just nullify */
-	BL		get_register,%r25
-	extrw,u         %r9,15,5,%r8           /* Get index register # */
-	cmpib,COND(=),n        -1,%r1,nadtlb_fault    /* have to use slow path */
-	copy            %r1,%r24
-	BL		get_register,%r25
-	extrw,u         %r9,10,5,%r8           /* Get base register # */
-	cmpib,COND(=),n        -1,%r1,nadtlb_fault    /* have to use slow path */
-	BL		set_register,%r25
-	add,l           %r1,%r24,%r1           /* doesn't affect c/b bits */
-
-nadtlb_nullify:
-	mfctl           %ipsw,%r8
-	ldil            L%PSW_N,%r9
-	or              %r8,%r9,%r8            /* Set PSW_N */
-	mtctl           %r8,%ipsw
-
-	rfir
-	nop
-
-	/* 
-		When there is no translation for the probe address then we
-		must nullify the insn and return zero in the target register.
-		This will indicate to the calling code that it does not have 
-		write/read privileges to this address.
-
-		This should technically work for prober and probew in PA 1.1,
-		and also probe,r and probe,w in PA 2.0
-
-		WARNING: USE ONLY NON-SHADOW REGISTERS WITH PROBE INSN!
-		THE SLOW-PATH EMULATION HAS NOT BEEN WRITTEN YET.
-
-	*/
-nadtlb_probe_check:
-	ldi             0x80,%r16
-	and             %r9,%r16,%r17
-	cmpb,<>,n       %r16,%r17,nadtlb_fault /* Must be probe,[rw]*/
-	BL              get_register,%r25      /* Find the target register */
-	extrw,u         %r9,31,5,%r8           /* Get target register */
-	cmpib,COND(=),n        -1,%r1,nadtlb_fault    /* have to use slow path */
-	BL		set_register,%r25
-	copy            %r0,%r1                /* Write zero to target register */
-	b nadtlb_nullify                       /* Nullify return insn */
-	nop
-
+	b,n		nadtlb_fault
 
 #ifdef CONFIG_64BIT
 itlb_miss_20w: