powerpc/64s: move the hash fault handling logic to C

The fault handling still has some complex logic particularly around
hash table handling, in asm. Implement most of this in C.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210130130852.2952424-6-npiggin@gmail.com

1 files changed, 49 insertions, 28 deletions

diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index 73b06adb6eeb..e866cae57e2f 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c
@@ -1512,16 +1512,40 @@ int hash_page(unsigned long ea, unsigned long access, unsigned long trap,
 }
 EXPORT_SYMBOL_GPL(hash_page);
 
-int __hash_page(unsigned long trap, unsigned long ea, unsigned long dsisr,
-		unsigned long msr)
+int do_hash_fault(struct pt_regs *regs, unsigned long ea, unsigned long dsisr)
 {
 	unsigned long access = _PAGE_PRESENT | _PAGE_READ;
 	unsigned long flags = 0;
-	struct mm_struct *mm = current->mm;
-	unsigned int region_id = get_region_id(ea);
+	struct mm_struct *mm;
+	unsigned int region_id;
+	int err;
+
+	if (unlikely(dsisr & (DSISR_BAD_FAULT_64S | DSISR_KEYFAULT)))
+		goto page_fault;
+
+	/*
+	 * If we are in an "NMI" (e.g., an interrupt when soft-disabled), then
+	 * don't call hash_page, just fail the fault. This is required to
+	 * prevent re-entrancy problems in the hash code, namely perf
+	 * interrupts hitting while something holds H_PAGE_BUSY, and taking a
+	 * hash fault. See the comment in hash_preload().
+	 *
+	 * We come here as a result of a DSI at a point where we don't want
+	 * to call hash_page, such as when we are accessing memory (possibly
+	 * user memory) inside a PMU interrupt that occurred while interrupts
+	 * were soft-disabled.  We want to invoke the exception handler for
+	 * the access, or panic if there isn't a handler.
+	 */
+	if (unlikely(in_nmi())) {
+		bad_page_fault(regs, ea, SIGSEGV);
+		return 0;
+	}
 
+	region_id = get_region_id(ea);
 	if ((region_id == VMALLOC_REGION_ID) || (region_id == IO_REGION_ID))
 		mm = &init_mm;
+	else
+		mm = current->mm;
 
 	if (dsisr & DSISR_NOHPTE)
 		flags |= HPTE_NOHPTE_UPDATE;
@@ -1537,13 +1561,31 @@ int __hash_page(unsigned long trap, unsigned long ea, unsigned long dsisr,
 	 * 2) user space access kernel space.
 	 */
 	access |= _PAGE_PRIVILEGED;
-	if ((msr & MSR_PR) || (region_id == USER_REGION_ID))
+	if (user_mode(regs) || (region_id == USER_REGION_ID))
 		access &= ~_PAGE_PRIVILEGED;
 
-	if (trap == 0x400)
+	if (regs->trap == 0x400)
 		access |= _PAGE_EXEC;
 
-	return hash_page_mm(mm, ea, access, trap, flags);
+	err = hash_page_mm(mm, ea, access, regs->trap, flags);
+	if (unlikely(err < 0)) {
+		// failed to instert a hash PTE due to an hypervisor error
+		if (user_mode(regs)) {
+			if (IS_ENABLED(CONFIG_PPC_SUBPAGE_PROT) && err == -2)
+				_exception(SIGSEGV, regs, SEGV_ACCERR, ea);
+			else
+				_exception(SIGBUS, regs, BUS_ADRERR, ea);
+		} else {
+			bad_page_fault(regs, ea, SIGBUS);
+		}
+		err = 0;
+
+	} else if (err) {
+page_fault:
+		err = do_page_fault(regs, ea, dsisr);
+	}
+
+	return err;
 }
 
 #ifdef CONFIG_PPC_MM_SLICES
@@ -1843,27 +1885,6 @@ void flush_hash_range(unsigned long number, int local)
 	}
 }
 
-/*
- * low_hash_fault is called when we the low level hash code failed
- * to instert a PTE due to an hypervisor error
- */
-void low_hash_fault(struct pt_regs *regs, unsigned long address, int rc)
-{
-	enum ctx_state prev_state = exception_enter();
-
-	if (user_mode(regs)) {
-#ifdef CONFIG_PPC_SUBPAGE_PROT
-		if (rc == -2)
-			_exception(SIGSEGV, regs, SEGV_ACCERR, address);
-		else
-#endif
-			_exception(SIGBUS, regs, BUS_ADRERR, address);
-	} else
-		bad_page_fault(regs, address, SIGBUS);
-
-	exception_exit(prev_state);
-}
-
 long hpte_insert_repeating(unsigned long hash, unsigned long vpn,
 			   unsigned long pa, unsigned long rflags,
 			   unsigned long vflags, int psize, int ssize)