powerpc/64s/hash: remove the vmalloc segment from the bolted SLB

Remove the vmalloc segment from bolted SLBEs. This is not required to
be bolted, and seems like it was added to help pre-load the SLB on
context switch. However there are now other segments like the vmemmap
segment and non-zero node memory that often take misses after a context
switch, so it is better to solve this in a more general way.

A subsequent change will track free SLB entries and uses those rather
than round-robin overwrite valid entries, which makes it far less
likely for kernel SLBEs to be evicted after they are installed.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/book3s/64/mmu-hash.h

@@ -30,7 +30,7 @@
  * SLB
  */
 
-#define SLB_NUM_BOLTED		3
+#define SLB_NUM_BOLTED		2
 #define SLB_CACHE_ENTRIES	8
 #define SLB_MIN_SIZE		32
 

arch/powerpc/mm/slb.c

@@ -30,8 +30,7 @@
 
 enum slb_index {
 	LINEAR_INDEX	= 0, /* Kernel linear map  (0xc000000000000000) */
-	VMALLOC_INDEX	= 1, /* Kernel virtual map (0xd000000000000000) */
-	KSTACK_INDEX	= 2, /* Kernel stack map */
+	KSTACK_INDEX	= 1, /* Kernel stack map */
 };
 
 extern void slb_allocate(unsigned long ea);
@@ -133,13 +132,11 @@ static void __slb_flush_and_rebolt(void)
 {
 	/* If you change this make sure you change SLB_NUM_BOLTED
 	 * and PR KVM appropriately too. */
-	unsigned long linear_llp, vmalloc_llp, lflags, vflags;
+	unsigned long linear_llp, lflags;
 	unsigned long ksp_esid_data, ksp_vsid_data;
 
 	linear_llp = mmu_psize_defs[mmu_linear_psize].sllp;
-	vmalloc_llp = mmu_psize_defs[mmu_vmalloc_psize].sllp;
 	lflags = SLB_VSID_KERNEL | linear_llp;
-	vflags = SLB_VSID_KERNEL | vmalloc_llp;
 
 	ksp_esid_data = mk_esid_data(get_paca()->kstack, mmu_kernel_ssize, KSTACK_INDEX);
 	if ((ksp_esid_data & ~0xfffffffUL) <= PAGE_OFFSET) {
@@ -157,14 +154,10 @@ static void __slb_flush_and_rebolt(void)
 	 * the stack between the slbia and rebolting it. */
 	asm volatile("isync\n"
 		     "slbia\n"
-		     /* Slot 1 - first VMALLOC segment */
+		     /* Slot 1 - kernel stack */
 		     "slbmte	%0,%1\n"
-		     /* Slot 2 - kernel stack */
-		     "slbmte	%2,%3\n"
 		     "isync"
-		     :: "r"(mk_vsid_data(VMALLOC_START, mmu_kernel_ssize, vflags)),
-		        "r"(mk_esid_data(VMALLOC_START, mmu_kernel_ssize, VMALLOC_INDEX)),
-		        "r"(ksp_vsid_data),
+		     :: "r"(ksp_vsid_data),
 		        "r"(ksp_esid_data)
 		     : "memory");
 }
@@ -256,10 +249,6 @@ void slb_dump_contents(struct slb_entry *slb_ptr)
 
 void slb_vmalloc_update(void)
 {
-	unsigned long vflags;
-
-	vflags = SLB_VSID_KERNEL | mmu_psize_defs[mmu_vmalloc_psize].sllp;
-	slb_shadow_update(VMALLOC_START, mmu_kernel_ssize, vflags, VMALLOC_INDEX);
 	slb_flush_and_rebolt();
 }
 
@@ -394,7 +383,7 @@ void slb_set_size(u16 size)
 void slb_initialize(void)
 {
 	unsigned long linear_llp, vmalloc_llp, io_llp;
-	unsigned long lflags, vflags;
+	unsigned long lflags;
 	static int slb_encoding_inited;
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
 	unsigned long vmemmap_llp;
@@ -430,14 +419,12 @@ void slb_initialize(void)
 	get_paca()->stab_rr = SLB_NUM_BOLTED - 1;
 
 	lflags = SLB_VSID_KERNEL | linear_llp;
-	vflags = SLB_VSID_KERNEL | vmalloc_llp;
 
 	/* Invalidate the entire SLB (even entry 0) & all the ERATS */
 	asm volatile("isync":::"memory");
 	asm volatile("slbmte  %0,%0"::"r" (0) : "memory");
 	asm volatile("isync; slbia; isync":::"memory");
 	create_shadowed_slbe(PAGE_OFFSET, mmu_kernel_ssize, lflags, LINEAR_INDEX);
-	create_shadowed_slbe(VMALLOC_START, mmu_kernel_ssize, vflags, VMALLOC_INDEX);
 
 	/* For the boot cpu, we're running on the stack in init_thread_union,
 	 * which is in the first segment of the linear mapping, and also