powerpc/mm: Add support for handling > 512TB address in SLB miss

For addresses above 512TB we allocate additional mmu contexts. To make
it all easy, addresses above 512TB are handled with IR/DR=1 and with
stack frame setup.

The mmu_context_t is also updated to track the new extended_ids. To
support upto 4PB we need a total 8 contexts.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
[mpe: Minor formatting tweaks and comment wording, switch BUG to WARN
      in get_ea_context().]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/book3s/64/hash-4k.h

@@ -11,6 +11,12 @@
 #define H_PUD_INDEX_SIZE  9
 #define H_PGD_INDEX_SIZE  9
 
+/*
+ * Each context is 512TB. But on 4k we restrict our max TASK size to 64TB
+ * Hence also limit max EA bits to 64TB.
+ */
+#define MAX_EA_BITS_PER_CONTEXT		46
+
 #ifndef __ASSEMBLY__
 #define H_PTE_TABLE_SIZE	(sizeof(pte_t) << H_PTE_INDEX_SIZE)
 #define H_PMD_TABLE_SIZE	(sizeof(pmd_t) << H_PMD_INDEX_SIZE)

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

@@ -7,6 +7,12 @@
 #define H_PUD_INDEX_SIZE  7
 #define H_PGD_INDEX_SIZE  8
 
+/*
+ * Each context is 512TB size. SLB miss for first context/default context
+ * is handled in the hotpath.
+ */
+#define MAX_EA_BITS_PER_CONTEXT		49
+
 /*
  * 64k aligned address free up few of the lower bits of RPN for us
  * We steal that here. For more deatils look at pte_pfn/pfn_pte()

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

@@ -91,7 +91,18 @@ struct slice_mask {
 };
 
 typedef struct {
+	union {
+		/*
+		 * We use id as the PIDR content for radix. On hash we can use
+		 * more than one id. The extended ids are used when we start
+		 * having address above 512TB. We allocate one extended id
+		 * for each 512TB. The new id is then used with the 49 bit
+		 * EA to build a new VA. We always use ESID_BITS_1T_MASK bits
+		 * from EA and new context ids to build the new VAs.
+		 */
 		mm_context_id_t id;
+		mm_context_id_t extended_id[TASK_SIZE_USER64/TASK_CONTEXT_SIZE];
+	};
 	u16 user_psize;		/* page size index */
 
 	/* Number of bits in the mm_cpumask */
@@ -196,5 +207,25 @@ extern void radix_init_pseries(void);
 static inline void radix_init_pseries(void) { };
 #endif
 
+static inline int get_ea_context(mm_context_t *ctx, unsigned long ea)
+{
+	int index = ea >> MAX_EA_BITS_PER_CONTEXT;
+
+	if (likely(index < ARRAY_SIZE(ctx->extended_id)))
+		return ctx->extended_id[index];
+
+	/* should never happen */
+	WARN_ON(1);
+	return 0;
+}
+
+static inline unsigned long get_user_vsid(mm_context_t *ctx,
+					  unsigned long ea, int ssize)
+{
+	unsigned long context = get_ea_context(ctx, ea);
+
+	return get_vsid(context, ea, ssize);
+}
+
 #endif /* __ASSEMBLY__ */
 #endif /* _ASM_POWERPC_BOOK3S_64_MMU_H_ */

arch/powerpc/include/asm/mmu_context.h

@@ -60,12 +60,51 @@ extern int hash__alloc_context_id(void);
 extern void hash__reserve_context_id(int id);
 extern void __destroy_context(int context_id);
 static inline void mmu_context_init(void) { }
+
+static inline int alloc_extended_context(struct mm_struct *mm,
+					 unsigned long ea)
+{
+	int context_id;
+
+	int index = ea >> MAX_EA_BITS_PER_CONTEXT;
+
+	context_id = hash__alloc_context_id();
+	if (context_id < 0)
+		return context_id;
+
+	VM_WARN_ON(mm->context.extended_id[index]);
+	mm->context.extended_id[index] = context_id;
+	return context_id;
+}
+
+static inline bool need_extra_context(struct mm_struct *mm, unsigned long ea)
+{
+	int context_id;
+
+	context_id = get_ea_context(&mm->context, ea);
+	if (!context_id)
+		return true;
+	return false;
+}
+
 #else
 extern void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next,
 			       struct task_struct *tsk);
 extern unsigned long __init_new_context(void);
 extern void __destroy_context(unsigned long context_id);
 extern void mmu_context_init(void);
+static inline int alloc_extended_context(struct mm_struct *mm,
+					 unsigned long ea)
+{
+	/* non book3s_64 should never find this called */
+	WARN_ON(1);
+	return -ENOMEM;
+}
+
+static inline bool need_extra_context(struct mm_struct *mm, unsigned long ea)
+{
+	return false;
+}
 #endif
 
 #if defined(CONFIG_KVM_BOOK3S_HV_POSSIBLE) && defined(CONFIG_PPC_RADIX_MMU)

arch/powerpc/include/asm/processor.h

@@ -119,9 +119,15 @@ void release_thread(struct task_struct *);
  */
 #define TASK_SIZE_USER64		TASK_SIZE_512TB
 #define DEFAULT_MAP_WINDOW_USER64	TASK_SIZE_128TB
+#define TASK_CONTEXT_SIZE		TASK_SIZE_512TB
 #else
 #define TASK_SIZE_USER64		TASK_SIZE_64TB
 #define DEFAULT_MAP_WINDOW_USER64	TASK_SIZE_64TB
+/*
+ * We don't need to allocate extended context ids for 4K page size, because
+ * we limit the max effective address on this config to 64TB.
+ */
+#define TASK_CONTEXT_SIZE		TASK_SIZE_64TB
 #endif
 
 /*

arch/powerpc/kernel/exceptions-64s.S

@@ -621,7 +621,10 @@ END_MMU_FTR_SECTION_IFCLR(MMU_FTR_TYPE_RADIX)
 	lwz	r9,PACA_EXSLB+EX_CCR(r13)	/* get saved CR */
 	mtlr	r10
 
-	beq-	8f		/* if bad address, make full stack frame */
+	/*
+	 * Large address, check whether we have to allocate new contexts.
+	 */
+	beq-	8f
 
 	bne-	cr5,2f		/* if unrecoverable exception, oops */
 
@@ -685,7 +688,7 @@ END_MMU_FTR_SECTION_IFCLR(MMU_FTR_TYPE_RADIX)
 	mr	r3,r12
 	mfspr	r11,SPRN_SRR0
 	mfspr	r12,SPRN_SRR1
-	LOAD_HANDLER(r10,bad_addr_slb)
+	LOAD_HANDLER(r10, large_addr_slb)
 	mtspr	SPRN_SRR0,r10
 	ld	r10,PACAKMSR(r13)
 	mtspr	SPRN_SRR1,r10
@@ -700,7 +703,7 @@ EXC_COMMON_BEGIN(unrecov_slb)
 	bl	unrecoverable_exception
 	b	1b
 
-EXC_COMMON_BEGIN(bad_addr_slb)
+EXC_COMMON_BEGIN(large_addr_slb)
 	EXCEPTION_PROLOG_COMMON(0x380, PACA_EXSLB)
 	RECONCILE_IRQ_STATE(r10, r11)
 	ld	r3, PACA_EXSLB+EX_DAR(r13)
@@ -710,7 +713,7 @@ EXC_COMMON_BEGIN(bad_addr_slb)
 	std	r10, _TRAP(r1)
 2:	bl	save_nvgprs
 	addi	r3, r1, STACK_FRAME_OVERHEAD
-	bl	slb_miss_bad_addr
+	bl	slb_miss_large_addr
 	b	ret_from_except
 
 EXC_REAL_BEGIN(hardware_interrupt, 0x500, 0x100)

arch/powerpc/kernel/traps.c

@@ -1495,18 +1495,6 @@ void alignment_exception(struct pt_regs *regs)
 	exception_exit(prev_state);
 }
 
-void slb_miss_bad_addr(struct pt_regs *regs)
-{
-	enum ctx_state prev_state = exception_enter();
-
-	if (user_mode(regs))
-		_exception(SIGSEGV, regs, SEGV_BNDERR, regs->dar);
-	else
-		bad_page_fault(regs, regs->dar, SIGSEGV);
-
-	exception_exit(prev_state);
-}
-
 void StackOverflow(struct pt_regs *regs)
 {
 	printk(KERN_CRIT "Kernel stack overflow in process %p, r1=%lx\n",

arch/powerpc/mm/copro_fault.c

@@ -112,7 +112,7 @@ int copro_calculate_slb(struct mm_struct *mm, u64 ea, struct copro_slb *slb)
 			return 1;
 		psize = get_slice_psize(mm, ea);
 		ssize = user_segment_size(ea);
-		vsid = get_vsid(mm->context.id, ea, ssize);
+		vsid = get_user_vsid(&mm->context, ea, ssize);
 		vsidkey = SLB_VSID_USER;
 		break;
 	case VMALLOC_REGION_ID:

arch/powerpc/mm/hash_utils_64.c

@@ -1267,7 +1267,7 @@ int hash_page_mm(struct mm_struct *mm, unsigned long ea,
 		}
 		psize = get_slice_psize(mm, ea);
 		ssize = user_segment_size(ea);
-		vsid = get_vsid(mm->context.id, ea, ssize);
+		vsid = get_user_vsid(&mm->context, ea, ssize);
 		break;
 	case VMALLOC_REGION_ID:
 		vsid = get_kernel_vsid(ea, mmu_kernel_ssize);
@@ -1532,7 +1532,7 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
 
 	/* Get VSID */
 	ssize = user_segment_size(ea);
-	vsid = get_vsid(mm->context.id, ea, ssize);
+	vsid = get_user_vsid(&mm->context, ea, ssize);
 	if (!vsid)
 		return;
 	/*

arch/powerpc/mm/mmu_context_book3s64.c

@@ -179,6 +179,19 @@ void __destroy_context(int context_id)
 }
 EXPORT_SYMBOL_GPL(__destroy_context);
 
+static void destroy_contexts(mm_context_t *ctx)
+{
+	int index, context_id;
+
+	spin_lock(&mmu_context_lock);
+	for (index = 0; index < ARRAY_SIZE(ctx->extended_id); index++) {
+		context_id = ctx->extended_id[index];
+		if (context_id)
+			ida_remove(&mmu_context_ida, context_id);
+	}
+	spin_unlock(&mmu_context_lock);
+}
+
 #ifdef CONFIG_PPC_64K_PAGES
 static void destroy_pagetable_page(struct mm_struct *mm)
 {
@@ -217,7 +230,7 @@ void destroy_context(struct mm_struct *mm)
 	else
 		subpage_prot_free(mm);
 	destroy_pagetable_page(mm);
-	__destroy_context(mm->context.id);
+	destroy_contexts(&mm->context);
 	mm->context.id = MMU_NO_CONTEXT;
 }
 

arch/powerpc/mm/pgtable-hash64.c

@@ -320,7 +320,7 @@ void hpte_do_hugepage_flush(struct mm_struct *mm, unsigned long addr,
 
 	if (!is_kernel_addr(addr)) {
 		ssize = user_segment_size(addr);
-		vsid = get_vsid(mm->context.id, addr, ssize);
+		vsid = get_user_vsid(&mm->context, addr, ssize);
 		WARN_ON(vsid == 0);
 	} else {
 		vsid = get_kernel_vsid(addr, mmu_kernel_ssize);

arch/powerpc/mm/slb.c

@@ -22,6 +22,7 @@
 #include <asm/cacheflush.h>
 #include <asm/smp.h>
 #include <linux/compiler.h>
+#include <linux/context_tracking.h>
 #include <linux/mm_types.h>
 
 #include <asm/udbg.h>
@@ -340,3 +341,110 @@ void slb_initialize(void)
 
 	asm volatile("isync":::"memory");
 }
+
+static void insert_slb_entry(unsigned long vsid, unsigned long ea,
+			     int bpsize, int ssize)
+{
+	unsigned long flags, vsid_data, esid_data;
+	enum slb_index index;
+	int slb_cache_index;
+
+	/*
+	 * We are irq disabled, hence should be safe to access PACA.
+	 */
+	index = get_paca()->stab_rr;
+
+	/*
+	 * simple round-robin replacement of slb starting at SLB_NUM_BOLTED.
+	 */
+	if (index < (mmu_slb_size - 1))
+		index++;
+	else
+		index = SLB_NUM_BOLTED;
+
+	get_paca()->stab_rr = index;
+
+	flags = SLB_VSID_USER | mmu_psize_defs[bpsize].sllp;
+	vsid_data = (vsid << slb_vsid_shift(ssize)) | flags |
+		    ((unsigned long) ssize << SLB_VSID_SSIZE_SHIFT);
+	esid_data = mk_esid_data(ea, ssize, index);
+
+	asm volatile("slbmte %0, %1" : : "r" (vsid_data), "r" (esid_data)
+		     : "memory");
+
+	/*
+	 * Now update slb cache entries
+	 */
+	slb_cache_index = get_paca()->slb_cache_ptr;
+	if (slb_cache_index < SLB_CACHE_ENTRIES) {
+		/*
+		 * We have space in slb cache for optimized switch_slb().
+		 * Top 36 bits from esid_data as per ISA
+		 */
+		get_paca()->slb_cache[slb_cache_index++] = esid_data >> 28;
+		get_paca()->slb_cache_ptr++;
+	} else {
+		/*
+		 * Our cache is full and the current cache content strictly
+		 * doesn't indicate the active SLB conents. Bump the ptr
+		 * so that switch_slb() will ignore the cache.
+		 */
+		get_paca()->slb_cache_ptr = SLB_CACHE_ENTRIES + 1;
+	}
+}
+
+static void handle_multi_context_slb_miss(int context_id, unsigned long ea)
+{
+	struct mm_struct *mm = current->mm;
+	unsigned long vsid;
+	int bpsize;
+
+	/*
+	 * We are always above 1TB, hence use high user segment size.
+	 */
+	vsid = get_vsid(context_id, ea, mmu_highuser_ssize);
+	bpsize = get_slice_psize(mm, ea);
+	insert_slb_entry(vsid, ea, bpsize, mmu_highuser_ssize);
+}
+
+void slb_miss_large_addr(struct pt_regs *regs)
+{
+	enum ctx_state prev_state = exception_enter();
+	unsigned long ea = regs->dar;
+	int context;
+
+	if (REGION_ID(ea) != USER_REGION_ID)
+		goto slb_bad_addr;
+
+	/*
+	 * Are we beyound what the page table layout supports ?
+	 */
+	if ((ea & ~REGION_MASK) >= H_PGTABLE_RANGE)
+		goto slb_bad_addr;
+
+	/* Lower address should have been handled by asm code */
+	if (ea < (1UL << MAX_EA_BITS_PER_CONTEXT))
+		goto slb_bad_addr;
+
+	/*
+	 * consider this as bad access if we take a SLB miss
+	 * on an address above addr limit.
+	 */
+	if (ea >= current->mm->context.slb_addr_limit)
+		goto slb_bad_addr;
+
+	context = get_ea_context(&current->mm->context, ea);
+	if (!context)
+		goto slb_bad_addr;
+
+	handle_multi_context_slb_miss(context, ea);
+	exception_exit(prev_state);
+	return;
+
+slb_bad_addr:
+	if (user_mode(regs))
+		_exception(SIGSEGV, regs, SEGV_BNDERR, ea);
+	else
+		bad_page_fault(regs, ea, SIGSEGV);
+	exception_exit(prev_state);
+}

arch/powerpc/mm/slb_low.S

@@ -75,10 +75,15 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_68_BIT_VA)
  */
 _GLOBAL(slb_allocate)
 	/*
-	 * check for bad kernel/user address
-	 * (ea & ~REGION_MASK) >= PGTABLE_RANGE
+	 * Check if the address falls within the range of the first context, or
+	 * if we may need to handle multi context. For the first context we
+	 * allocate the slb entry via the fast path below. For large address we
+	 * branch out to C-code and see if additional contexts have been
+	 * allocated.
+	 * The test here is:
+	 *   (ea & ~REGION_MASK) >= (1ull << MAX_EA_BITS_PER_CONTEXT)
 	 */
-	rldicr. r9,r3,4,(63 - H_PGTABLE_EADDR_SIZE - 4)
+	rldicr. r9,r3,4,(63 - MAX_EA_BITS_PER_CONTEXT - 4)
 	bne-	8f
 
 	srdi	r9,r3,60		/* get region */

arch/powerpc/mm/slice.c

@@ -648,6 +648,15 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
 	slice_print_mask(" mask", &potential_mask);
 
  convert:
+	/*
+	 * Try to allocate the context before we do slice convert
+	 * so that we handle the context allocation failure gracefully.
+	 */
+	if (need_extra_context(mm, newaddr)) {
+		if (alloc_extended_context(mm, newaddr) < 0)
+			return -ENOMEM;
+	}
+
 	slice_andnot_mask(&potential_mask, &potential_mask, &good_mask);
 	if (compat_maskp && !fixed)
 		slice_andnot_mask(&potential_mask, &potential_mask, compat_maskp);
@@ -658,10 +667,14 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
 		if (psize > MMU_PAGE_BASE)
 			on_each_cpu(slice_flush_segments, mm, 1);
 	}
+	return newaddr;
 
 return_addr:
+	if (need_extra_context(mm, newaddr)) {
+		if (alloc_extended_context(mm, newaddr) < 0)
+			return -ENOMEM;
+	}
 	return newaddr;
-
 }
 EXPORT_SYMBOL_GPL(slice_get_unmapped_area);
 

arch/powerpc/mm/tlb_hash64.c

@@ -89,7 +89,7 @@ void hpte_need_flush(struct mm_struct *mm, unsigned long addr,
 	/* Build full vaddr */
 	if (!is_kernel_addr(addr)) {
 		ssize = user_segment_size(addr);
-		vsid = get_vsid(mm->context.id, addr, ssize);
+		vsid = get_user_vsid(&mm->context, addr, ssize);
 	} else {
 		vsid = get_kernel_vsid(addr, mmu_kernel_ssize);
 		ssize = mmu_kernel_ssize;