ACPI, APEI, Add ERST record ID cache

APEI ERST firmware interface and implementation has no multiple users
in mind.  For example, if there is four records in storage with ID: 1,
2, 3 and 4, if two ERST readers enumerate the records via
GET_NEXT_RECORD_ID as follow,

reader 1		reader 2
1
			2
3
			4
-1
			-1

where -1 signals there is no more record ID.

Reader 1 has no chance to check record 2 and 4, while reader 2 has no
chance to check record 1 and 3.  And any other GET_NEXT_RECORD_ID will
return -1, that is, other readers will has no chance to check any
record even they are not cleared by anyone.

This makes raw GET_NEXT_RECORD_ID not suitable for used by multiple
users.

To solve the issue, an in-memory ERST record ID cache is designed and
implemented.  When enumerating record ID, the ID returned by
GET_NEXT_RECORD_ID is added into cache in addition to be returned to
caller.  So other readers can check the cache to get all record ID
available.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 26 insertions, 16 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce-apei.c b/arch/x86/kernel/cpu/mcheck/mce-apei.c
index 8209472b27a5..83930deec3c6 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-apei.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-apei.c
@@ -106,24 +106,34 @@ int apei_write_mce(struct mce *m)
 ssize_t apei_read_mce(struct mce *m, u64 *record_id)
 {
         struct cper_mce_record rcd;
-        ssize_t len;
-
-        len = erst_read_next(&rcd.hdr, sizeof(rcd));
-        if (len <= 0)
-                return len;
-        /* Can not skip other records in storage via ERST unless clear them */
-        else if (len != sizeof(rcd) ||
-                 uuid_le_cmp(rcd.hdr.creator_id, CPER_CREATOR_MCE)) {
-                if (printk_ratelimit())
-                        pr_warning(
-                        "MCE-APEI: Can not skip the unknown record in ERST");
-                return -EIO;
-        }
-
+        int rc, pos;
+
+        rc = erst_get_record_id_begin(&pos);
+        if (rc)
+                return rc;
+retry:
+        rc = erst_get_record_id_next(&pos, record_id);
+        if (rc)
+                goto out;
+        /* no more record */
+        if (*record_id == APEI_ERST_INVALID_RECORD_ID)
+                goto out;
+        rc = erst_read(*record_id, &rcd.hdr, sizeof(rcd));
+        /* someone else has cleared the record, try next one */
+        if (rc == -ENOENT)
+                goto retry;
+        else if (rc < 0)
+                goto out;
+        /* try to skip other type records in storage */
+        else if (rc != sizeof(rcd) ||
+                 uuid_le_cmp(rcd.hdr.creator_id, CPER_CREATOR_MCE))
+                goto retry;
         memcpy(m, &rcd.mce, sizeof(*m));
-        *record_id = rcd.hdr.record_id;
+        rc = sizeof(*m);
+out:
+        erst_get_record_id_end();
 
-        return sizeof(*m);
+        return rc;
 }
 
 /* Check whether there is record in ERST */