Patchwork : sparc64: Validate linear D-TLB misses.

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Submitter David Miller
Date Aug. 26, 2009, 3:37 a.m.
Message ID <20090825.203716.227878711.davem@davemloft.net>
Download mbox | patch
Permalink /patch/32104/
State Accepted
Delegated to: David Miller
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Comments

David Miller - Aug. 26, 2009, 3:37 a.m.
From: David Miller <davem@davemloft.net>
Date: Mon, 24 Aug 2009 23:23:49 -0700 (PDT)

> Heyong-ssi, can you try your test case with the following
> updated patch?  It works quite well for me.
> 
> sparc64: Validate linear D-TLB misses.

Ok I added one more safety check, and the following is
what I'm going to push to Linus tonight.

sparc64: Validate linear D-TLB misses.

When page alloc debugging is not enabled, we essentially accept any
virtual address for linear kernel TLB misses.  But with kgdb, kernel
address probing, and other facilities we can try to access arbitrary
crap.

So, make sure the address we miss on will translate to physical memory
that actually exists.

In order to make this work we have to embed the valid address bitmap
into the kernel image.  And in order to make that less expensive we
make an adjustment, in that the max physical memory address is
decreased to "1 << 41", even on the chips that support a 42-bit
physical address space.  We can do this because bit 41 indicates
"I/O space" and thus covers non-memory ranges.

The result of this is that:

1) kpte_linear_bitmap shrinks from 2K to 1K in size

2) we need 64K more for the valid address bitmap

We can't let the valid address bitmap be dynamically allocated
once we start using it to validate TLB misses, otherwise we have
crazy issues to deal with wrt. recursive TLB misses and such.

If we're in a TLB miss it could be the deepest trap level that's legal
inside of the cpu.  So if we TLB miss referencing the bitmap, the cpu
will be out of trap levels and enter RED state.

To guard against out-of-range accesses to the bitmap, we have to check
to make sure no bits in the physical address above bit 40 are set.  We
could export and use last_valid_pfn for this check, but that's just an
unnecessary extra memory reference.

On the plus side of all this, since we load all of these translations
into the special 4MB mapping TSB, and we check the TSB first for TLB
misses, there should be absolutely no real cost for these new checks
in the TLB miss path.

Reported-by: heyongli@gmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 arch/sparc/include/asm/pgtable_64.h |   12 +++++++--
 arch/sparc/kernel/ktlb.S            |   42 ++++++++++++++++++++++++++++++---
 arch/sparc/mm/init_64.c             |   43 +++++++++++++++++++---------------
 arch/sparc/mm/init_64.h             |    7 ++++-
 4 files changed, 76 insertions(+), 28 deletions(-)
Jim Gifford - Aug. 28, 2009, 12:18 a.m.
> 2009/8/27 Jim Gifford <maillist@jg555.com>:
>   
>>
>>
>> Dave, This also seems to fix the error I was having on the Netra X1, so far
>> it's been up 24 hours with no issues.
>>
>>     

Spoke too soon, it's started again. So that patch has only delayed the 
issue.

Aug 24 05:53:19 mail kernel: [   81.739235] EXT3 FS on hda2, internal 
journal
Aug 24 05:53:19 mail kernel: [   82.649915] Adding 1510088k swap on 
/dev/hda4.  Priority:-1 extents:1 across:1510088k
Aug 27 01:58:01 mail kernel: [72307.489683] ------------[ cut here 
]------------
Aug 27 01:58:01 mail kernel: [72307.489738] WARNING: at 
net/sched/sch_generic.c:226 dev_watchdog+0x24c/0x260()
Aug 27 01:58:01 mail kernel: [72307.489754] NETDEV WATCHDOG: eth1 
(tulip): transmit timed out
Aug 27 01:58:01 mail kernel: [72307.489766] Modules linked in: tulip 
bitrev crc32
Aug 27 01:58:01 mail kernel: [72307.489786] Call Trace:
Aug 27 01:58:01 mail kernel: [72307.489808]  [0000000000452308] 
warn_slowpath_fmt+0x28/0x40
Aug 27 01:58:01 mail kernel: [72307.489829]  [000000000060420c] 
dev_watchdog+0x24c/0x260
Aug 27 01:58:01 mail kernel: [72307.489851]  [000000000045c520] 
run_timer_softirq+0x180/0x200
Aug 27 01:58:01 mail kernel: [72307.489875]  [00000000004577e8] 
__do_softirq+0xa8/0x180
Aug 27 01:58:01 mail kernel: [72307.489897]  [000000000042a470] 
do_softirq+0x70/0xa0
Aug 27 01:58:01 mail kernel: [72307.489916]  [0000000000457478] 
irq_exit+0x78/0xa0
Aug 27 01:58:01 mail kernel: [72307.489938]  [000000000042f578] 
timer_interrupt+0x58/0xa0
Aug 27 01:58:01 mail kernel: [72307.489959]  [00000000004209d4] 
tl0_irq14+0x14/0x20
Aug 27 01:58:01 mail kernel: [72307.489976]  [000000000042c408] 
cpu_idle+0x48/0xe0
Aug 27 01:58:01 mail kernel: [72307.490002]  [000000000074e738] 
start_kernel+0x278/0x2b4
Aug 27 01:58:01 mail kernel: [72307.490028]  [000000000065c344] 
tlb_fixup_done+0x80/0x9c
Aug 27 01:58:01 mail kernel: [72307.490041]  [0000000000000000] (null)
Aug 27 01:58:01 mail kernel: [72307.490053] ---[ end trace 
ab817fc60b30ccb6 ]---
Aug 27 01:58:01 mail kernel: [72307.491397] 0000:00:05.0: 
tulip_stop_rxtx() failed (CSR5 0xfc508100 CSR6 0x20e8000)
Aug 27 01:58:09 mail kernel: [72315.487043] 0000:00:05.0: 
tulip_stop_rxtx() failed (CSR5 0xfc508100 CSR6 0x20e8000)
Aug 27 01:58:17 mail kernel: [72323.483023] 0000:00:05.0: 
tulip_stop_rxtx() failed (CSR5 0xfc508100 CSR6 0x20e8000)
Aug 27 01:58:25 mail kernel: [72331.478976] 0000:00:05.0: 
tulip_stop_rxtx() failed (CSR5 0xfc508100 CSR6 0x20e8000)

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David Miller - Aug. 28, 2009, 4:14 a.m.
From: Jim Gifford <maillist@jg555.com>
Date: Thu, 27 Aug 2009 17:18:39 -0700

> Spoke too soon, it's started again. So that patch has only delayed the
> issue.

It wasn't meant to fix your bug so this is no surprise
to me.
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Patch

diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index b049abf..0ff92fa 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -726,11 +726,17 @@  extern unsigned long pte_file(pte_t);
 extern pte_t pgoff_to_pte(unsigned long);
 #define PTE_FILE_MAX_BITS	(64UL - PAGE_SHIFT - 1UL)
 
-extern unsigned long *sparc64_valid_addr_bitmap;
+extern unsigned long sparc64_valid_addr_bitmap[];
 
 /* Needs to be defined here and not in linux/mm.h, as it is arch dependent */
-#define kern_addr_valid(addr)	\
-	(test_bit(__pa((unsigned long)(addr))>>22, sparc64_valid_addr_bitmap))
+static inline bool kern_addr_valid(unsigned long addr)
+{
+	unsigned long paddr = __pa(addr);
+
+	if ((paddr >> 41UL) != 0UL)
+		return false;
+	return test_bit(paddr >> 22, sparc64_valid_addr_bitmap);
+}
 
 extern int page_in_phys_avail(unsigned long paddr);
 
diff --git a/arch/sparc/kernel/ktlb.S b/arch/sparc/kernel/ktlb.S
index cef8def..3ea6e8c 100644
--- a/arch/sparc/kernel/ktlb.S
+++ b/arch/sparc/kernel/ktlb.S
@@ -151,12 +151,46 @@  kvmap_dtlb_4v:
 	 * Must preserve %g1 and %g6 (TAG).
 	 */
 kvmap_dtlb_tsb4m_miss:
-	sethi		%hi(kpte_linear_bitmap), %g2
-	or		%g2, %lo(kpte_linear_bitmap), %g2
+	/* Clear the PAGE_OFFSET top virtual bits, shift
+	 * down to get PFN, and make sure PFN is in range.
+	 */
+	sllx		%g4, 21, %g5
 
-	/* Clear the PAGE_OFFSET top virtual bits, then shift
-	 * down to get a 256MB physical address index.
+	/* Check to see if we know about valid memory at the 4MB
+	 * chunk this physical address will reside within.
 	 */
+	srlx		%g5, 21 + 41, %g2
+	brnz,pn		%g2, kvmap_dtlb_longpath
+	 nop
+
+	/* This unconditional branch and delay-slot nop gets patched
+	 * by the sethi sequence once the bitmap is properly setup.
+	 */
+	.globl		valid_addr_bitmap_insn
+valid_addr_bitmap_insn:
+	ba,pt		%xcc, 2f
+	 nop
+	.subsection	2
+	.globl		valid_addr_bitmap_patch
+valid_addr_bitmap_patch:
+	sethi		%hi(sparc64_valid_addr_bitmap), %g7
+	or		%g7, %lo(sparc64_valid_addr_bitmap), %g7
+	.previous
+
+	srlx		%g5, 21 + 22, %g2
+	srlx		%g2, 6, %g5
+	and		%g2, 63, %g2
+	sllx		%g5, 3, %g5
+	ldx		[%g7 + %g5], %g5
+	mov		1, %g7
+	sllx		%g7, %g2, %g7
+	andcc		%g5, %g7, %g0
+	be,pn		%xcc, kvmap_dtlb_longpath
+
+2:	 sethi		%hi(kpte_linear_bitmap), %g2
+	or		%g2, %lo(kpte_linear_bitmap), %g2
+
+	/* Get the 256MB physical address index. */
 	sllx		%g4, 21, %g5
 	mov		1, %g7
 	srlx		%g5, 21 + 28, %g5
diff --git a/arch/sparc/mm/init_64.c b/arch/sparc/mm/init_64.c
index ed6be6b..a70a5e1 100644
--- a/arch/sparc/mm/init_64.c
+++ b/arch/sparc/mm/init_64.c
@@ -145,7 +145,8 @@  static void __init read_obp_memory(const char *property,
 	     cmp_p64, NULL);
 }
 
-unsigned long *sparc64_valid_addr_bitmap __read_mostly;
+unsigned long sparc64_valid_addr_bitmap[VALID_ADDR_BITMAP_BYTES /
+					sizeof(unsigned long)];
 EXPORT_SYMBOL(sparc64_valid_addr_bitmap);
 
 /* Kernel physical address base and size in bytes.  */
@@ -1874,7 +1875,7 @@  static int pavail_rescan_ents __initdata;
  * memory list again, and make sure it provides at least as much
  * memory as 'pavail' does.
  */
-static void __init setup_valid_addr_bitmap_from_pavail(void)
+static void __init setup_valid_addr_bitmap_from_pavail(unsigned long *bitmap)
 {
 	int i;
 
@@ -1897,8 +1898,7 @@  static void __init setup_valid_addr_bitmap_from_pavail(void)
 
 				if (new_start <= old_start &&
 				    new_end >= (old_start + PAGE_SIZE)) {
-					set_bit(old_start >> 22,
-						sparc64_valid_addr_bitmap);
+					set_bit(old_start >> 22, bitmap);
 					goto do_next_page;
 				}
 			}
@@ -1919,20 +1919,21 @@  static void __init setup_valid_addr_bitmap_from_pavail(void)
 	}
 }
 
+static void __init patch_tlb_miss_handler_bitmap(void)
+{
+	extern unsigned int valid_addr_bitmap_insn[];
+	extern unsigned int valid_addr_bitmap_patch[];
+
+	valid_addr_bitmap_insn[1] = valid_addr_bitmap_patch[1];
+	mb();
+	valid_addr_bitmap_insn[0] = valid_addr_bitmap_patch[0];
+	flushi(&valid_addr_bitmap_insn[0]);
+}
+
 void __init mem_init(void)
 {
 	unsigned long codepages, datapages, initpages;
 	unsigned long addr, last;
-	int i;
-
-	i = last_valid_pfn >> ((22 - PAGE_SHIFT) + 6);
-	i += 1;
-	sparc64_valid_addr_bitmap = (unsigned long *) alloc_bootmem(i << 3);
-	if (sparc64_valid_addr_bitmap == NULL) {
-		prom_printf("mem_init: Cannot alloc valid_addr_bitmap.\n");
-		prom_halt();
-	}
-	memset(sparc64_valid_addr_bitmap, 0, i << 3);
 
 	addr = PAGE_OFFSET + kern_base;
 	last = PAGE_ALIGN(kern_size) + addr;
@@ -1941,15 +1942,19 @@  void __init mem_init(void)
 		addr += PAGE_SIZE;
 	}
 
-	setup_valid_addr_bitmap_from_pavail();
+	setup_valid_addr_bitmap_from_pavail(sparc64_valid_addr_bitmap);
+	patch_tlb_miss_handler_bitmap();
 
 	high_memory = __va(last_valid_pfn << PAGE_SHIFT);
 
 #ifdef CONFIG_NEED_MULTIPLE_NODES
-	for_each_online_node(i) {
-		if (NODE_DATA(i)->node_spanned_pages != 0) {
-			totalram_pages +=
-				free_all_bootmem_node(NODE_DATA(i));
+	{
+		int i;
+		for_each_online_node(i) {
+			if (NODE_DATA(i)->node_spanned_pages != 0) {
+				totalram_pages +=
+					free_all_bootmem_node(NODE_DATA(i));
+			}
 		}
 	}
 #else
diff --git a/arch/sparc/mm/init_64.h b/arch/sparc/mm/init_64.h
index 1606387..c2f772d 100644
--- a/arch/sparc/mm/init_64.h
+++ b/arch/sparc/mm/init_64.h
@@ -5,10 +5,13 @@ 
  * marked non-static so that assembler code can get at them.
  */
 
-#define MAX_PHYS_ADDRESS	(1UL << 42UL)
-#define KPTE_BITMAP_CHUNK_SZ	(256UL * 1024UL * 1024UL)
+#define MAX_PHYS_ADDRESS	(1UL << 41UL)
+#define KPTE_BITMAP_CHUNK_SZ		(256UL * 1024UL * 1024UL)
 #define KPTE_BITMAP_BYTES	\
 	((MAX_PHYS_ADDRESS / KPTE_BITMAP_CHUNK_SZ) / 8)
+#define VALID_ADDR_BITMAP_CHUNK_SZ	(4UL * 1024UL * 1024UL)
+#define VALID_ADDR_BITMAP_BYTES	\
+	((MAX_PHYS_ADDRESS / VALID_ADDR_BITMAP_CHUNK_SZ) / 8)
 
 extern unsigned long kern_linear_pte_xor[2];
 extern unsigned long kpte_linear_bitmap[KPTE_BITMAP_BYTES / sizeof(unsigned long)];