[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>

1 files changed, 16 insertions, 12 deletions

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;
         }