svn commit: r354235 - head/sys/powerpc/booke

[Justin Hibbits]

Author: jhibbits
Date: Fri Nov  1 02:55:58 2019
New Revision: 354235
URL: https://svnweb.freebsd.org/changeset/base/354235

Log:
  powerpc/booke: Fix TLB1 entry accounting
  
  It's possible, with per-CPU mappings, for TLB1 indices to get out of sync.
  This presents a problem when trying to insert an entry into TLB1 of all
  CPUs.  Currently that's done by assuming (hoping) that the TLBs are
  perfectly synced, and inserting to the same index for all CPUs.  However,
  with aforementioned private mappings, this can result in overwriting
  mappings on the other CPUs.
  
  An example:
  
      CPU0                    CPU1
      <setup all mappings>    <idle>
          3 private mappings
        kick off CPU 1
                              initialize shared mappings (3 indices low)
                              Load kernel module, triggers 20 new mappings
        Sync mappings at N-3
                              initialize 3 private mappings.
  
  At this point, CPU 1 has all the correct mappings, while CPU 0 is missing 3
  mappings that were shared across to CPU 1.  When CPU 0 tries to access
  memory in one of the overwritten mappings, it hangs while tripping through
  the TLB miss handler.  Device mappings are not stored in any page table.
  
  This fixes by introducing a '-1' index for tlb1_write_entry_int(), so each
  CPU searches for an available index private to itself.
  
  MFC after:	3 weeks

Modified:
  head/sys/powerpc/booke/pmap.c

Modified: head/sys/powerpc/booke/pmap.c
==============================================================================
--- head/sys/powerpc/booke/pmap.c	Fri Nov  1 02:48:43 2019	(r354234)
+++ head/sys/powerpc/booke/pmap.c	Fri Nov  1 02:55:58 2019	(r354235)
@@ -1881,7 +1881,7 @@ mmu_booke_bootstrap(mmu_t mmu, vm_offset_t start, vm_o
 }
 
 #ifdef SMP
- void
+void
 tlb1_ap_prep(void)
 {
 	tlb_entry_t *e, tmp;
@@ -3776,14 +3776,34 @@ struct tlbwrite_args {
 	unsigned int idx;
 };
 
+static uint32_t
+tlb1_find_free(void)
+{
+	tlb_entry_t e;
+	int i;
+
+	for (i = 0; i < TLB1_ENTRIES; i++) {
+		tlb1_read_entry(&e, i);
+		if ((e.mas1 & MAS1_VALID) == 0)
+			return (i);
+	}
+	return (-1);
+}
+
 static void
 tlb1_write_entry_int(void *arg)
 {
 	struct tlbwrite_args *args = arg;
-	uint32_t mas0;
+	uint32_t idx, mas0;
 
+	idx = args->idx;
+	if (idx == -1) {
+		idx = tlb1_find_free();
+		if (idx == -1)
+			panic("No free TLB1 entries!\n");
+	}
 	/* Select entry */
-	mas0 = MAS0_TLBSEL(1) | MAS0_ESEL(args->idx);
+	mas0 = MAS0_TLBSEL(1) | MAS0_ESEL(idx);
 
 	mtspr(SPR_MAS0, mas0);
 	mtspr(SPR_MAS1, args->e->mas1);
@@ -3897,10 +3917,9 @@ tlb1_set_entry(vm_offset_t va, vm_paddr_t pa, vm_size_
 	uint32_t ts, tid;
 	int tsize, index;
 
+	/* First try to update an existing entry. */
 	for (index = 0; index < TLB1_ENTRIES; index++) {
 		tlb1_read_entry(&e, index);
-		if ((e.mas1 & MAS1_VALID) == 0)
-			break;
 		/* Check if we're just updating the flags, and update them. */
 		if (e.phys == pa && e.virt == va && e.size == size) {
 			e.mas2 = (va & MAS2_EPN_MASK) | flags;
@@ -3908,10 +3927,6 @@ tlb1_set_entry(vm_offset_t va, vm_paddr_t pa, vm_size_
 			return (0);
 		}
 	}
-	if (index >= TLB1_ENTRIES) {
-		printf("tlb1_set_entry: TLB1 full!\n");
-		return (-1);
-	}
 
 	/* Convert size to TSIZE */
 	tsize = size2tsize(size);
@@ -3931,13 +3946,8 @@ tlb1_set_entry(vm_offset_t va, vm_paddr_t pa, vm_size_
 	e.mas3 = (pa & MAS3_RPN) | MAS3_SR | MAS3_SW | MAS3_SX;
 	e.mas7 = (pa >> 32) & MAS7_RPN;
 
-	tlb1_write_entry(&e, index);
+	tlb1_write_entry(&e, -1);
 
-	/*
-	 * XXX in general TLB1 updates should be propagated between CPUs,
-	 * since current design assumes to have the same TLB1 set-up on all
-	 * cores.
-	 */
 	return (0);
 }