[IA64-SGI] Silent data corruption caused by XPC V2.

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>

5 files changed, 47 insertions, 35 deletions

diff --git a/arch/ia64/sn/kernel/xpc_channel.c b/arch/ia64/sn/kernel/xpc_channel.c
index c2f69f7942af..1f3540826e68 100644
--- a/arch/ia64/sn/kernel/xpc_channel.c
+++ b/arch/ia64/sn/kernel/xpc_channel.c
@@ -279,8 +279,8 @@ xpc_pull_remote_cachelines(struct xpc_partition *part, void *dst,
                 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;
         }
diff --git a/arch/ia64/sn/kernel/xpc_main.c b/arch/ia64/sn/kernel/xpc_main.c
index 5e8e59efb347..4d026f9dd98b 100644
--- a/arch/ia64/sn/kernel/xpc_main.c
+++ b/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;
         }
 
diff --git a/arch/ia64/sn/kernel/xpc_partition.c b/arch/ia64/sn/kernel/xpc_partition.c
index 2a89cfce4954..57c723f5cba4 100644
--- a/arch/ia64/sn/kernel/xpc_partition.c
+++ b/arch/ia64/sn/kernel/xpc_partition.c
@@ -71,19 +71,15 @@ struct xpc_partition xpc_partitions[XP_MAX_PARTITIONS + 1];
  * 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 *discovered_nasids,
 
 
         /* 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, struct xpc_vars *remote_vars)
                 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 partid, void *nasid_mask)
 
         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);
diff --git a/include/asm-ia64/sn/xp.h b/include/asm-ia64/sn/xp.h
index 9bd2f9bf329b..6f807e0193b7 100644
--- a/include/asm-ia64/sn/xp.h
+++ b/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;
diff --git a/include/asm-ia64/sn/xpc.h b/include/asm-ia64/sn/xpc.h
index b72af597878d..35e1386f37ab 100644
--- a/include/asm-ia64/sn/xpc.h
+++ b/include/asm-ia64/sn/xpc.h
@@ -683,7 +683,9 @@ 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);