[PATCH v7 19/25] ACPI / APEI: Only use queued estatus entry during _in_nmi_notify_one()

James Morse
2018-12-03T18:07:46Z

Each struct ghes has an worst-case sized buffer for storing the
estatus. If an error is being processed by ghes_proc() in process
context this buffer will be in use. If the error source then triggers
an NMI-like notification, the same buffer will be used by
_in_nmi_notify_one() to stage the estatus data, before
__process_error() copys it into a queued estatus entry.

Merge __process_error()s work into _in_nmi_notify_one() so that
the queued estatus entry is used from the beginning. Use the new
ghes_peek_estatus() to know how much memory to allocate from
the ghes_estatus_pool before reading the records.

Reported-by: Borislav Petkov <bp@suse.de>
Signed-off-by: James Morse <james.morse@arm.com>

Change since v6:
* Added a comment explaining the 'ack-error, then goto no_work'.
* Added missing esatus-clearing, which is necessary after reading the GAS,
---
drivers/acpi/apei/ghes.c | 59 ++++++++++++++++++++++++----------------
1 file changed, 35 insertions(+), 24 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 07a12aac4c1a..849da0d43a21 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -856,43 +856,43 @@ static void ghes_print_queued_estatus(void)
}
}

-/* Save estatus for further processing in IRQ context */
-static void __process_error(struct ghes *ghes,
- struct acpi_hest_generic_status *src_estatus)
+static int _in_nmi_notify_one(struct ghes *ghes, int fixmap_idx)
{
- u32 len, node_len;
+ struct acpi_hest_generic_status *estatus, tmp_header;
struct ghes_estatus_node *estatus_node;
- struct acpi_hest_generic_status *estatus;
+ u32 len, node_len;
+ u64 buf_paddr;
+ int sev, rc;

if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG))
- return;
+ return -EOPNOTSUPP;

- if (ghes_estatus_cached(src_estatus))
- return;
+ rc = __ghes_peek_estatus(ghes, fixmap_idx, &tmp_header, &buf_paddr);
+ if (rc) {
+ ghes_clear_estatus(&tmp_header, buf_paddr, fixmap_idx);
+ return rc;
+ }

- len = cper_estatus_len(src_estatus);
- node_len = GHES_ESTATUS_NODE_LEN(len);
+ rc = __ghes_check_estatus(ghes, &tmp_header);
+ if (rc) {
+ ghes_clear_estatus(&tmp_header, buf_paddr, fixmap_idx);
+ return rc;
+ }

+ len = cper_estatus_len(&tmp_header);
+ node_len = GHES_ESTATUS_NODE_LEN(len);
estatus_node = (void *)gen_pool_alloc(ghes_estatus_pool, node_len);
if (!estatus_node)
- return;
+ return -ENOMEM;

estatus_node->ghes = ghes;
estatus_node->generic = ghes->generic;
estatus = GHES_ESTATUS_FROM_NODE(estatus_node);
- memcpy(estatus, src_estatus, len);
- llist_add(&estatus_node->llnode, &ghes_estatus_llist);
-}
-
-static int _in_nmi_notify_one(struct ghes *ghes, int fixmap_idx)
-{
- struct acpi_hest_generic_status *estatus = ghes->estatus;
- u64 buf_paddr;
- int sev;

- if (ghes_read_estatus(ghes, estatus, &buf_paddr, fixmap_idx)) {
+ if (__ghes_read_estatus(estatus, buf_paddr, len, fixmap_idx)) {
ghes_clear_estatus(estatus, buf_paddr, fixmap_idx);
- return -ENOENT;
+ rc = -ENOENT;
+ goto no_work;
}

sev = ghes_severity(estatus->error_severity);
@@ -901,14 +901,25 @@ static int _in_nmi_notify_one(struct ghes *ghes, int fixmap_idx)
__ghes_panic(ghes, estatus);
}

- __process_error(ghes, estatus);
ghes_clear_estatus(estatus, buf_paddr, fixmap_idx);

if (is_hest_type_generic_v2(ghes) && ghes_ack_error(ghes->generic_v2))
pr_warn_ratelimited(FW_WARN GHES_PFX
"Failed to ack error status block!\n");

- return 0;
+ /* This error has been reported before, don't process it again. */
+ if (ghes_estatus_cached(estatus))
+ goto no_work;
+
+ llist_add(&estatus_node->llnode, &ghes_estatus_llist);
+
+ return rc;
+
+no_work:
+ gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node,
+ node_len);
+
+ return rc;
}

static int ghes_estatus_queue_notified(struct list_head *rcu_list,
--
2.19.2