KVM: PPC: Book3S PR: Rework SLB switching code

On LPAR guest systems Linux enables the shadow SLB to indicate to the
hypervisor a number of SLB entries that always have to be available.

Today we go through this shadow SLB and disable all ESID's valid bits.
However, pHyp doesn't like this approach very much and honors us with
fancy machine checks.

Fortunately the shadow SLB descriptor also has an entry that indicates
the number of valid entries following. During the lifetime of a guest
we can just swap that value to 0 and don't have to worry about the
SLB restoration magic.

While we're touching the code, let's also make it more readable (get
rid of rldicl), allow it to deal with a dynamic number of bolted
SLB entries and only do shadow SLB swizzling on LPAR systems.

Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/kernel/paca.c

@@ -98,6 +98,9 @@ static inline void free_lppacas(void) { }
 /*
  * 3 persistent SLBs are registered here.  The buffer will be zero
  * initially, hence will all be invaild until we actually write them.
+ *
+ * If you make the number of persistent SLB entries dynamic, please also
+ * update PR KVM to flush and restore them accordingly.
  */
 static struct slb_shadow *slb_shadow;
 

arch/powerpc/kvm/book3s_64_slb.S

@@ -17,29 +17,9 @@
  * Authors: Alexander Graf <agraf@suse.de>
  */
 
-#define SHADOW_SLB_ESID(num)	(SLBSHADOW_SAVEAREA + (num * 0x10))
-#define SHADOW_SLB_VSID(num)	(SLBSHADOW_SAVEAREA + (num * 0x10) + 0x8)
-#define UNBOLT_SLB_ENTRY(num) \
-	li	r11, SHADOW_SLB_ESID(num);	\
-	LDX_BE	r9, r12, r11;			\
-	/* Invalid? Skip. */;			\
-	rldicl. r0, r9, 37, 63;			\
-	beq	slb_entry_skip_ ## num;		\
-	xoris	r9, r9, SLB_ESID_V@h;		\
-	STDX_BE	r9, r12, r11;			\
-  slb_entry_skip_ ## num:
-
-#define REBOLT_SLB_ENTRY(num) \
-	li	r8, SHADOW_SLB_ESID(num);	\
-	li	r7, SHADOW_SLB_VSID(num);	\
-	LDX_BE	r10, r11, r8;			\
-	cmpdi	r10, 0;				\
-	beq	slb_exit_skip_ ## num;		\
-	oris	r10, r10, SLB_ESID_V@h;		\
-	LDX_BE	r9, r11, r7;			\
-	slbmte	r9, r10;			\
-	STDX_BE	r10, r11, r8;			\
-slb_exit_skip_ ## num:
+#define SHADOW_SLB_ENTRY_LEN	0x10
+#define OFFSET_ESID(x)		(SHADOW_SLB_ENTRY_LEN * x)
+#define OFFSET_VSID(x)		((SHADOW_SLB_ENTRY_LEN * x) + 8)
 
 /******************************************************************************
  *                                                                            *
@@ -63,20 +43,15 @@ slb_exit_skip_ ## num:
 	 * SVCPU[LR]  = guest LR
 	 */
 
-	/* Remove LPAR shadow entries */
+BEGIN_FW_FTR_SECTION
 
-#if SLB_NUM_BOLTED == 3
+	/* Declare SLB shadow as 0 entries big */
 
-	ld	r12, PACA_SLBSHADOWPTR(r13)
+	ld	r11, PACA_SLBSHADOWPTR(r13)
+	li	r8, 0
+	stb	r8, 3(r11)
 
-	/* Remove bolted entries */
-	UNBOLT_SLB_ENTRY(0)
-	UNBOLT_SLB_ENTRY(1)
-	UNBOLT_SLB_ENTRY(2)
-
-#else
-#error unknown number of bolted entries
-#endif
+END_FW_FTR_SECTION_IFSET(FW_FEATURE_LPAR)
 
 	/* Flush SLB */
 
@@ -99,7 +74,7 @@ slb_loop_enter:
 
 	ld	r10, 0(r11)
 
-	rldicl. r0, r10, 37, 63
+	andis.	r9, r10, SLB_ESID_V@h
 	beq	slb_loop_enter_skip
 
 	ld	r9, 8(r11)
@@ -136,24 +111,42 @@ slb_do_enter:
 	 *
 	 */
 
-	/* Restore bolted entries from the shadow and fix it along the way */
+	/* Remove all SLB entries that are in use. */
 
 	li	r0, r0
 	slbmte	r0, r0
 	slbia
-	isync
 
-#if SLB_NUM_BOLTED == 3
+	/* Restore bolted entries from the shadow */
 
 	ld	r11, PACA_SLBSHADOWPTR(r13)
 
-	REBOLT_SLB_ENTRY(0)
-	REBOLT_SLB_ENTRY(1)
-	REBOLT_SLB_ENTRY(2)
-
-#else
-#error unknown number of bolted entries
-#endif
+BEGIN_FW_FTR_SECTION
+
+	/* Declare SLB shadow as SLB_NUM_BOLTED entries big */
+
+	li	r8, SLB_NUM_BOLTED
+	stb	r8, 3(r11)
+
+END_FW_FTR_SECTION_IFSET(FW_FEATURE_LPAR)
+
+	/* Manually load all entries from shadow SLB */
+
+	li	r8, SLBSHADOW_SAVEAREA
+	li	r7, SLBSHADOW_SAVEAREA + 8
+
+	.rept	SLB_NUM_BOLTED
+	LDX_BE	r10, r11, r8
+	cmpdi	r10, 0
+	beq	1f
+	LDX_BE	r9, r11, r7
+	slbmte	r9, r10
+1:	addi	r7, r7, SHADOW_SLB_ENTRY_LEN
+	addi	r8, r8, SHADOW_SLB_ENTRY_LEN
+	.endr
+
+	isync
+	sync
 
 slb_do_exit:
 

arch/powerpc/mm/slb.c

@@ -97,7 +97,7 @@ static inline void create_shadowed_slbe(unsigned long ea, int ssize,
 static void __slb_flush_and_rebolt(void)
 {
 	/* If you change this make sure you change SLB_NUM_BOLTED
-	 * appropriately too. */
+	 * and PR KVM appropriately too. */
 	unsigned long linear_llp, vmalloc_llp, lflags, vflags;
 	unsigned long ksp_esid_data, ksp_vsid_data;