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Subject[patch 25/37] Silent data corruption caused by XPC
-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Robin Holt <holt@sgi.com>

Jack Steiner identified a problem where XPC can cause a silent
data corruption. On module load, the placement may cause the
xpc_remote_copy_buffer to span two physical pages. DMA transfers are
done to the start virtual address translated to physical.

This patch changes the buffer from a statically allocated buffer to a
kmalloc'd buffer. Dean Nelson reviewed this before posting. I have
tested it in the configuration that was showing the memory corruption
and verified it works. I also added a BUG_ON statement to help catch
this if a similar situation is encountered.

Signed-off-by: Robin Holt <holt@sgi.com>
Signed-off-by: Dean Nelson <dcn@sgi.com>
Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/ia64/sn/kernel/xpc_channel.c | 4 ++--
arch/ia64/sn/kernel/xpc_main.c | 28 ++++++++++++++++------------
arch/ia64/sn/kernel/xpc_partition.c | 24 ++++++++----------------
include/asm-ia64/sn/xp.h | 22 ++++++++++++++++++----
include/asm-ia64/sn/xpc.h | 4 +++-
5 files changed, 47 insertions(+), 35 deletions(-)

--- linux-2.6.17.11.orig/arch/ia64/sn/kernel/xpc_channel.c
+++ linux-2.6.17.11/arch/ia64/sn/kernel/xpc_channel.c
@@ -279,8 +279,8 @@ xpc_pull_remote_cachelines(struct xpc_pa
return part->reason;
}

- bte_ret = xp_bte_copy((u64) src, (u64) ia64_tpa((u64) dst),
- (u64) cnt, (BTE_NORMAL | BTE_WACQUIRE), NULL);
+ bte_ret = xp_bte_copy((u64) src, (u64) dst, (u64) cnt,
+ (BTE_NORMAL | BTE_WACQUIRE), NULL);
if (bte_ret == BTE_SUCCESS) {
return xpcSuccess;
}
--- linux-2.6.17.11.orig/arch/ia64/sn/kernel/xpc_main.c
+++ linux-2.6.17.11/arch/ia64/sn/kernel/xpc_main.c
@@ -1052,6 +1052,8 @@ xpc_do_exit(enum xpc_retval reason)
if (xpc_sysctl) {
unregister_sysctl_table(xpc_sysctl);
}
+
+ kfree(xpc_remote_copy_buffer_base);
}


@@ -1212,24 +1214,20 @@ xpc_init(void)
partid_t partid;
struct xpc_partition *part;
pid_t pid;
+ size_t buf_size;


if (!ia64_platform_is("sn2")) {
return -ENODEV;
}

- /*
- * xpc_remote_copy_buffer is used as a temporary buffer for bte_copy'ng
- * various portions of a partition's reserved page. Its size is based
- * on the size of the reserved page header and part_nasids mask. So we
- * need to ensure that the other items will fit as well.
- */
- if (XPC_RP_VARS_SIZE > XPC_RP_HEADER_SIZE + XP_NASID_MASK_BYTES) {
- dev_err(xpc_part, "xpc_remote_copy_buffer is not big enough\n");
- return -EPERM;
- }
- DBUG_ON((u64) xpc_remote_copy_buffer !=
- L1_CACHE_ALIGN((u64) xpc_remote_copy_buffer));
+
+ buf_size = max(XPC_RP_VARS_SIZE,
+ XPC_RP_HEADER_SIZE + XP_NASID_MASK_BYTES);
+ xpc_remote_copy_buffer = xpc_kmalloc_cacheline_aligned(buf_size,
+ GFP_KERNEL, &xpc_remote_copy_buffer_base);
+ if (xpc_remote_copy_buffer == NULL)
+ return -ENOMEM;

snprintf(xpc_part->bus_id, BUS_ID_SIZE, "part");
snprintf(xpc_chan->bus_id, BUS_ID_SIZE, "chan");
@@ -1293,6 +1291,8 @@ xpc_init(void)
if (xpc_sysctl) {
unregister_sysctl_table(xpc_sysctl);
}
+
+ kfree(xpc_remote_copy_buffer_base);
return -EBUSY;
}

@@ -1311,6 +1311,8 @@ xpc_init(void)
if (xpc_sysctl) {
unregister_sysctl_table(xpc_sysctl);
}
+
+ kfree(xpc_remote_copy_buffer_base);
return -EBUSY;
}

@@ -1362,6 +1364,8 @@ xpc_init(void)
if (xpc_sysctl) {
unregister_sysctl_table(xpc_sysctl);
}
+
+ kfree(xpc_remote_copy_buffer_base);
return -EBUSY;
}

--- linux-2.6.17.11.orig/arch/ia64/sn/kernel/xpc_partition.c
+++ linux-2.6.17.11/arch/ia64/sn/kernel/xpc_partition.c
@@ -71,19 +71,15 @@ struct xpc_partition xpc_partitions[XP_M
* Generic buffer used to store a local copy of portions of a remote
* partition's reserved page (either its header and part_nasids mask,
* or its vars).
- *
- * xpc_discovery runs only once and is a seperate thread that is
- * very likely going to be processing in parallel with receiving
- * interrupts.
*/
-char ____cacheline_aligned xpc_remote_copy_buffer[XPC_RP_HEADER_SIZE +
- XP_NASID_MASK_BYTES];
+char *xpc_remote_copy_buffer;
+void *xpc_remote_copy_buffer_base;


/*
* Guarantee that the kmalloc'd memory is cacheline aligned.
*/
-static void *
+void *
xpc_kmalloc_cacheline_aligned(size_t size, gfp_t flags, void **base)
{
/* see if kmalloc will give us cachline aligned memory by default */
@@ -148,7 +144,7 @@ xpc_get_rsvd_page_pa(int nasid)
}
}

- bte_res = xp_bte_copy(rp_pa, ia64_tpa(buf), buf_len,
+ bte_res = xp_bte_copy(rp_pa, buf, buf_len,
(BTE_NOTIFY | BTE_WACQUIRE), NULL);
if (bte_res != BTE_SUCCESS) {
dev_dbg(xpc_part, "xp_bte_copy failed %i\n", bte_res);
@@ -447,7 +443,7 @@ xpc_check_remote_hb(void)

/* pull the remote_hb cache line */
bres = xp_bte_copy(part->remote_vars_pa,
- ia64_tpa((u64) remote_vars),
+ (u64) remote_vars,
XPC_RP_VARS_SIZE,
(BTE_NOTIFY | BTE_WACQUIRE), NULL);
if (bres != BTE_SUCCESS) {
@@ -498,8 +494,7 @@ xpc_get_remote_rp(int nasid, u64 *discov


/* pull over the reserved page header and part_nasids mask */
-
- bres = xp_bte_copy(*remote_rp_pa, ia64_tpa((u64) remote_rp),
+ bres = xp_bte_copy(*remote_rp_pa, (u64) remote_rp,
XPC_RP_HEADER_SIZE + xp_nasid_mask_bytes,
(BTE_NOTIFY | BTE_WACQUIRE), NULL);
if (bres != BTE_SUCCESS) {
@@ -554,11 +549,8 @@ xpc_get_remote_vars(u64 remote_vars_pa,
return xpcVarsNotSet;
}

-
/* pull over the cross partition variables */
-
- bres = xp_bte_copy(remote_vars_pa, ia64_tpa((u64) remote_vars),
- XPC_RP_VARS_SIZE,
+ bres = xp_bte_copy(remote_vars_pa, (u64) remote_vars, XPC_RP_VARS_SIZE,
(BTE_NOTIFY | BTE_WACQUIRE), NULL);
if (bres != BTE_SUCCESS) {
return xpc_map_bte_errors(bres);
@@ -1239,7 +1231,7 @@ xpc_initiate_partid_to_nasids(partid_t p

part_nasid_pa = (u64) XPC_RP_PART_NASIDS(part->remote_rp_pa);

- bte_res = xp_bte_copy(part_nasid_pa, ia64_tpa((u64) nasid_mask),
+ bte_res = xp_bte_copy(part_nasid_pa, (u64) nasid_mask,
xp_nasid_mask_bytes, (BTE_NOTIFY | BTE_WACQUIRE), NULL);

return xpc_map_bte_errors(bte_res);
--- linux-2.6.17.11.orig/include/asm-ia64/sn/xp.h
+++ linux-2.6.17.11/include/asm-ia64/sn/xp.h
@@ -60,23 +60,37 @@
* the bte_copy() once in the hope that the failure was due to a temporary
* aberration (i.e., the link going down temporarily).
*
- * See bte_copy for definition of the input parameters.
+ * src - physical address of the source of the transfer.
+ * vdst - virtual address of the destination of the transfer.
+ * len - number of bytes to transfer from source to destination.
+ * mode - see bte_copy() for definition.
+ * notification - see bte_copy() for definition.
*
* Note: xp_bte_copy() should never be called while holding a spinlock.
*/
static inline bte_result_t
-xp_bte_copy(u64 src, u64 dest, u64 len, u64 mode, void *notification)
+xp_bte_copy(u64 src, u64 vdst, u64 len, u64 mode, void *notification)
{
bte_result_t ret;
+ u64 pdst = ia64_tpa(vdst);


- ret = bte_copy(src, dest, len, mode, notification);
+ /*
+ * Ensure that the physically mapped memory is contiguous.
+ *
+ * We do this by ensuring that the memory is from region 7 only.
+ * If the need should arise to use memory from one of the other
+ * regions, then modify the BUG_ON() statement to ensure that the
+ * memory from that region is always physically contiguous.
+ */
+ BUG_ON(REGION_NUMBER(vdst) != RGN_KERNEL);

+ ret = bte_copy(src, pdst, len, mode, notification);
if (ret != BTE_SUCCESS) {
if (!in_interrupt()) {
cond_resched();
}
- ret = bte_copy(src, dest, len, mode, notification);
+ ret = bte_copy(src, pdst, len, mode, notification);
}

return ret;
--- linux-2.6.17.11.orig/include/asm-ia64/sn/xpc.h
+++ linux-2.6.17.11/include/asm-ia64/sn/xpc.h
@@ -684,7 +684,9 @@ extern struct xpc_vars *xpc_vars;
extern struct xpc_rsvd_page *xpc_rsvd_page;
extern struct xpc_vars_part *xpc_vars_part;
extern struct xpc_partition xpc_partitions[XP_MAX_PARTITIONS + 1];
-extern char xpc_remote_copy_buffer[];
+extern char *xpc_remote_copy_buffer;
+extern void *xpc_remote_copy_buffer_base;
+extern void *xpc_kmalloc_cacheline_aligned(size_t, gfp_t, void **);
extern struct xpc_rsvd_page *xpc_rsvd_page_init(void);
extern void xpc_allow_IPI_ops(void);
extern void xpc_restrict_IPI_ops(void);
--
-
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