Pseudo-locking can work when Code and Data Prioritization (CDP) is enabled, but there are a few additional checks and actions involved. At this time it is not clear if users would want to use pseudo-locking and CDP at the same time so the support of this is delayed until we understand the usage better.
Disable pseudo-locking if CDP is enabled. Add the details of things to keep in mind for anybody considering enabling this support. Signed-off-by: Reinette Chatre <reinette.cha...@intel.com> --- arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c | 30 +++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c b/arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c index a0c144b5b09b..f6932a7de6e7 100644 --- a/arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c +++ b/arch/x86/kernel/cpu/intel_rdt_pseudo_lock.c @@ -443,6 +443,36 @@ int rdt_pseudo_lock_fs_init(struct kernfs_node *root) lockdep_assert_held(&rdtgroup_mutex); /* + * Pseudo-locking not supported when CDP is enabled. + * + * Some things to consider if you would like to enable this support + * (using L3 CDP as example): + * - When CDP is enabled two separate resources are exposed, L3DATA + * and L3CODE, but they are actually on the same cache. The + * implication for pseudo-locking is that if a pseudo-locked + * region is created on a domain of one resource (eg. L3CODE), + * then a pseudo-locked region cannot be created on that same + * domain of the other resource (eg. L3DATA). This is because + * the creation of a pseudo-locked region involves a call to + * wbinvd that will affect all cache allocations on particular + * domain. + * - Considering the previous, it may be possible to only expose + * one of the CDP resources to pseudo-locking and hide the other. + * For example, we could consider to only expose L3DATA and since + * the L3 cache is unified it is still possible to place + * instructions there are execute it. + * - If only one region is exposed to pseudo-locking we should still + * keep in mind that availability of a portion of cache for + * pseudo-locking should take into account both resources. Similarly, + * if a pseudo-locked region is created in one resource, the portion + * of cache used by it should be made unavailable to all future + * allocations from both resources. + */ + if (rdt_resources_all[RDT_RESOURCE_L3DATA].alloc_enabled || + rdt_resources_all[RDT_RESOURCE_L2DATA].alloc_enabled) + return 0; + + /* * Not knowing the bits to disable prefetching is not a failure * that should be propagated since we only return prefetching bits * for those platforms pseudo-locking has been tested on. If -- 2.13.6