From: Reinette Chatre <reinette.chatre@intel.com>
To: tglx@linutronix.de, fenghua.yu@intel.com, tony.luck@intel.com
Cc: gavin.hindman@intel.com, vikas.shivappa@linux.intel.com,
dave.hansen@intel.com, mingo@redhat.com, hpa@zytor.com,
x86@kernel.org, linux-kernel@vger.kernel.org,
Reinette Chatre <reinette.chatre@intel.com>
Subject: [RFC PATCH V2 10/22] x86/intel_rdt: Disable pseudo-locking if CDP enabled
Date: Tue, 13 Feb 2018 07:46:54 -0800 [thread overview]
Message-ID: <e55972642c15170c9cce78cf24dabde3df8d6c6b.1518443616.git.reinette.chatre@intel.com> (raw)
In-Reply-To: <cover.1518443616.git.reinette.chatre@intel.com>
In-Reply-To: <cover.1518443616.git.reinette.chatre@intel.com>
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.chatre@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
next prev parent reply other threads:[~2018-02-13 23:52 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-13 15:46 [RFC PATCH V2 00/22] Intel(R) Resource Director Technology Cache Pseudo-Locking enabling Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 01/22] x86/intel_rdt: Documentation for Cache Pseudo-Locking Reinette Chatre
2018-02-19 20:35 ` Thomas Gleixner
2018-02-19 22:15 ` Reinette Chatre
2018-02-19 22:19 ` Thomas Gleixner
2018-02-19 22:24 ` Reinette Chatre
2018-02-19 21:27 ` Randy Dunlap
2018-02-19 22:21 ` Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 02/22] x86/intel_rdt: Make useful functions available internally Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 03/22] x86/intel_rdt: Introduce hooks to create pseudo-locking files Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 04/22] x86/intel_rdt: Introduce test to determine if closid is in use Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 05/22] x86/intel_rdt: Print more accurate pseudo-locking availability Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 06/22] x86/intel_rdt: Create pseudo-locked regions Reinette Chatre
2018-02-19 20:57 ` Thomas Gleixner
2018-02-19 23:02 ` Reinette Chatre
2018-02-19 23:16 ` Thomas Gleixner
2018-02-20 3:21 ` Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 07/22] x86/intel_rdt: Connect pseudo-locking directory to operations Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 08/22] x86/intel_rdt: Introduce pseudo-locking resctrl files Reinette Chatre
2018-02-19 21:01 ` Thomas Gleixner
2018-02-13 15:46 ` [RFC PATCH V2 09/22] x86/intel_rdt: Discover supported platforms via prefetch disable bits Reinette Chatre
2018-02-13 15:46 ` Reinette Chatre [this message]
2018-02-13 15:46 ` [RFC PATCH V2 11/22] x86/intel_rdt: Associate pseudo-locked regions with its domain Reinette Chatre
2018-02-19 21:19 ` Thomas Gleixner
2018-02-19 23:00 ` Reinette Chatre
2018-02-19 23:19 ` Thomas Gleixner
2018-02-20 3:17 ` Reinette Chatre
2018-02-20 10:00 ` Thomas Gleixner
2018-02-20 16:02 ` Reinette Chatre
2018-02-20 17:18 ` Thomas Gleixner
2018-02-13 15:46 ` [RFC PATCH V2 12/22] x86/intel_rdt: Support CBM checking from value and character buffer Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 13/22] x86/intel_rdt: Support schemata write - pseudo-locking core Reinette Chatre
2018-02-20 17:15 ` Thomas Gleixner
2018-02-20 18:47 ` Reinette Chatre
2018-02-20 23:21 ` Thomas Gleixner
2018-02-21 1:58 ` Mike Kravetz
2018-02-21 6:10 ` Reinette Chatre
2018-02-21 8:34 ` Thomas Gleixner
2018-02-21 5:58 ` Reinette Chatre
2018-02-27 0:34 ` Reinette Chatre
2018-02-27 10:36 ` Thomas Gleixner
2018-02-27 15:38 ` Thomas Gleixner
2018-02-27 19:52 ` Reinette Chatre
2018-02-27 21:33 ` Reinette Chatre
2018-02-28 18:39 ` Thomas Gleixner
2018-02-28 19:17 ` Reinette Chatre
2018-02-28 19:40 ` Thomas Gleixner
2018-02-27 21:01 ` Reinette Chatre
2018-02-28 17:57 ` Thomas Gleixner
2018-02-28 17:59 ` Thomas Gleixner
2018-02-28 18:34 ` Reinette Chatre
2018-02-28 18:42 ` Thomas Gleixner
2018-02-13 15:46 ` [RFC PATCH V2 14/22] x86/intel_rdt: Enable testing for pseudo-locked region Reinette Chatre
2018-02-13 15:46 ` [RFC PATCH V2 15/22] x86/intel_rdt: Prevent new allocations from pseudo-locked regions Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 16/22] x86/intel_rdt: Create debugfs files for pseudo-locking testing Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 17/22] x86/intel_rdt: Create character device exposing pseudo-locked region Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 18/22] x86/intel_rdt: More precise L2 hit/miss measurements Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 19/22] x86/intel_rdt: Support L3 cache performance event of Broadwell Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 20/22] x86/intel_rdt: Limit C-states dynamically when pseudo-locking active Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 21/22] mm/hugetlb: Enable large allocations through gigantic page API Reinette Chatre
2018-02-13 15:47 ` [RFC PATCH V2 22/22] x86/intel_rdt: Support contiguous memory of all sizes Reinette Chatre
2018-02-14 18:12 ` [RFC PATCH V2 00/22] Intel(R) Resource Director Technology Cache Pseudo-Locking enabling Mike Kravetz
2018-02-14 18:31 ` Reinette Chatre
2018-02-15 20:39 ` Reinette Chatre
2018-02-15 21:10 ` Mike Kravetz
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