From 70b565bbdb911023373e035225ab10077e4ab937 Mon Sep 17 00:00:00 2001 From: Vaibhav Jain Date: Fri, 14 Oct 2016 15:08:36 +0530 Subject: 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 Reviewed-by: Andrew Donnellan Signed-off-by: Vaibhav Jain Signed-off-by: Michael Ellerman --- drivers/misc/cxl/sysfs.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) (limited to 'drivers/misc/cxl/sysfs.c') diff --git a/drivers/misc/cxl/sysfs.c b/drivers/misc/cxl/sysfs.c index b043c20f158f..a8b6d6a635e9 100644 --- a/drivers/misc/cxl/sysfs.c +++ b/drivers/misc/cxl/sysfs.c @@ -75,12 +75,31 @@ static ssize_t reset_adapter_store(struct device *device, int val; rc = sscanf(buf, "%i", &val); - if ((rc != 1) || (val != 1)) + if ((rc != 1) || (val != 1 && val != -1)) return -EINVAL; - if ((rc = cxl_ops->adapter_reset(adapter))) - return rc; - return count; + /* + * See if we can lock the context mapping that's only allowed + * when there are no contexts attached to the adapter. Once + * taken this will also prevent any context from getting activated. + */ + if (val == 1) { + rc = cxl_adapter_context_lock(adapter); + if (rc) + goto out; + + rc = cxl_ops->adapter_reset(adapter); + /* In case reset failed release context lock */ + if (rc) + cxl_adapter_context_unlock(adapter); + + } else if (val == -1) { + /* Perform a forced adapter reset */ + rc = cxl_ops->adapter_reset(adapter); + } + +out: + return rc ? rc : count; } static ssize_t load_image_on_perst_show(struct device *device, -- cgit v1.2.3