On 12/10/16 15:17, Vaibhav Jain wrote:
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.

Signed-off-by: Vaibhav Jain <vaib...@linux.vnet.ibm.com>

All the changes look good to me.

Reviewed-by: Andrew Donnellan <andrew.donnel...@au1.ibm.com>

diff --git a/Documentation/ABI/testing/sysfs-class-cxl 
index 4ba0a2a..dae2b38 100644
--- a/Documentation/ABI/testing/sysfs-class-cxl
+++ b/Documentation/ABI/testing/sysfs-class-cxl
@@ -220,8 +220,11 @@ What:           /sys/class/cxl/<card>/reset
 Date:           October 2014
 Contact:        linuxppc-dev@lists.ozlabs.org
 Description:    write only
-                Writing 1 will issue a PERST to card which may cause the card
-                to reload the FPGA depending on load_image_on_perst.
+                Writing 1 will issue a PERST to card provided there are no
+               contexts active on any one of the card AFUs. This may cause
+               the card to reload the FPGA depending on load_image_on_perst.
+               Writing -1 will do a force PERST irrespective of any active
+               contexts on the card AFUs.

Ugh, spaces vs tabs bites again :(

Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnel...@au1.ibm.com  IBM Australia Limited

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