cxl: Prevent adapter reset if an active context exists
This patch prevents resetting the cxl adapter via sysfs in presence of
one or more active cxl_context on it. This protects against an
unrecoverable error caused by PSL owning a dirty cache line even after
reset and host tries to touch the same cache line. In case a force reset
of the card is required irrespective of any active contexts, the int
value -1 can be stored in the 'reset' sysfs attribute of the card.
The patch introduces a new atomic_t member named contexts_num inside
struct cxl that holds the number of active context attached to the card
, which is checked against '0' before proceeding with the reset. To
prevent against a race condition where a context is activated just after
reset check is performed, the contexts_num is atomically set to '-1'
after reset-check to indicate that no more contexts can be activated on
the card anymore.
Before activating a context we atomically test if contexts_num is
non-negative and if so, increment its value by one. In case the value of
contexts_num is negative then it indicates that the card is about to be
reset and context activation is error-ed out at that point.
Fixes: 62fa19d4b4fd ("cxl: Add ability to reset the card")
Cc: stable@vger.kernel.org # v4.0+
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/drivers/misc/cxl/main.c b/drivers/misc/cxl/main.c
index d9be23b2..62e0dfb 100644
--- a/drivers/misc/cxl/main.c
+++ b/drivers/misc/cxl/main.c
@@ -243,8 +243,10 @@ struct cxl *cxl_alloc_adapter(void)
if (dev_set_name(&adapter->dev, "card%i", adapter->adapter_num))
goto err2;
- return adapter;
+ /* start with context lock taken */
+ atomic_set(&adapter->contexts_num, -1);
+ return adapter;
err2:
cxl_remove_adapter_nr(adapter);
err1:
@@ -286,6 +288,44 @@ int cxl_afu_select_best_mode(struct cxl_afu *afu)
return 0;
}
+int cxl_adapter_context_get(struct cxl *adapter)
+{
+ int rc;
+
+ rc = atomic_inc_unless_negative(&adapter->contexts_num);
+ return rc >= 0 ? 0 : -EBUSY;
+}
+
+void cxl_adapter_context_put(struct cxl *adapter)
+{
+ atomic_dec_if_positive(&adapter->contexts_num);
+}
+
+int cxl_adapter_context_lock(struct cxl *adapter)
+{
+ int rc;
+ /* no active contexts -> contexts_num == 0 */
+ rc = atomic_cmpxchg(&adapter->contexts_num, 0, -1);
+ return rc ? -EBUSY : 0;
+}
+
+void cxl_adapter_context_unlock(struct cxl *adapter)
+{
+ int val = atomic_cmpxchg(&adapter->contexts_num, -1, 0);
+
+ /*
+ * contexts lock taken -> contexts_num == -1
+ * If not true then show a warning and force reset the lock.
+ * This will happen when context_unlock was requested without
+ * doing a context_lock.
+ */
+ if (val != -1) {
+ atomic_set(&adapter->contexts_num, 0);
+ WARN(1, "Adapter context unlocked with %d active contexts",
+ val);
+ }
+}
+
static int __init init_cxl(void)
{
int rc = 0;