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/cxl.h | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) (limited to 'drivers/misc/cxl/cxl.h') diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h index 01d372aba131..a144073593fa 100644 --- a/drivers/misc/cxl/cxl.h +++ b/drivers/misc/cxl/cxl.h @@ -618,6 +618,14 @@ struct cxl { bool perst_select_user; bool perst_same_image; bool psl_timebase_synced; + + /* + * number of contexts mapped on to this card. Possible values are: + * >0: Number of contexts mapped and new one can be mapped. + * 0: No active contexts and new ones can be mapped. + * -1: No contexts mapped and new ones cannot be mapped. + */ + atomic_t contexts_num; }; int cxl_pci_alloc_one_irq(struct cxl *adapter); @@ -944,4 +952,20 @@ bool cxl_pci_is_vphb_device(struct pci_dev *dev); /* decode AFU error bits in the PSL register PSL_SERR_An */ void cxl_afu_decode_psl_serr(struct cxl_afu *afu, u64 serr); + +/* + * Increments the number of attached contexts on an adapter. + * In case an adapter_context_lock is taken the return -EBUSY. + */ +int cxl_adapter_context_get(struct cxl *adapter); + +/* Decrements the number of attached contexts on an adapter */ +void cxl_adapter_context_put(struct cxl *adapter); + +/* If no active contexts then prevents contexts from being attached */ +int cxl_adapter_context_lock(struct cxl *adapter); + +/* Unlock the contexts-lock if taken. Warn and force unlock otherwise */ +void cxl_adapter_context_unlock(struct cxl *adapter); + #endif -- cgit v1.2.3