[Xen-devel] [PATCH v2 4/4] docs: add document to introduce CDP command

[He Chen <he.chen@xxxxxxxxxxxxxxx>]

Add CDP command in xl interface man page and add description of CDP
in xl-psr.markdown.

Signed-off-by: He Chen <he.chen@xxxxxxxxxxxxxxx>
---
 docs/man/xl.pod.1         | 14 ++++++++++++++
 docs/misc/xl-psr.markdown | 44 +++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/docs/man/xl.pod.1 b/docs/man/xl.pod.1
index f22c3f3..3801039 100644
--- a/docs/man/xl.pod.1
+++ b/docs/man/xl.pod.1
@@ -1530,6 +1530,12 @@ applications. In the Xen implementation, CAT is used to 
control cache allocation
 on VM basis. To enforce cache on a specific domain, just set capacity bitmasks
 (CBM) for the domain.
 
+Intel Broadwell and later server platforms also offer Code/Data Prioritization
+(CDP) for cache allocation, which support specify code or data cache for
+applications. CDP is used on VM basis in the Xen implementation. To specify
+code or data CBM for the domain, CDP feature must be enabled and CBM type
+options need to be specified when setting CBM.
+
 =over 4
 
 =item B<psr-cat-cbm-set> [I<OPTIONS>] I<domain-id> I<cbm>
@@ -1545,6 +1551,14 @@ B<OPTIONS>
 
 Specify the socket to process, otherwise all sockets are processed.
 
+=item B<-c>, B<--code>
+
+Set code CBM with CDP enabled.
+
+=item B<-d>, B<--data>
+
+Set data CBM with CDP enabled.
+
 =back
 
 =item B<psr-cat-show> [I<domain-id>]
diff --git a/docs/misc/xl-psr.markdown b/docs/misc/xl-psr.markdown
index 3545912..4c77737 100644
--- a/docs/misc/xl-psr.markdown
+++ b/docs/misc/xl-psr.markdown
@@ -14,7 +14,7 @@ tracks cache utilization of memory accesses according to the 
RMID and reports
 monitored data via a counter register.
 
 For more detailed information please refer to Intel SDM chapter
-"17.14 - Platform Shared Resource Monitoring: Cache Monitoring Technology".
+"17.15 - Platform Shared Resource Monitoring: Cache Monitoring Technology".
 
 In Xen's implementation, each domain in the system can be assigned a RMID
 independently, while RMID=0 is reserved for monitoring domains that don't
@@ -91,17 +91,44 @@ For example, assuming a system with 8 portions and 3 
domains:
    first domain exclusive access to half the cache, and the other two exclusive
    access to one quarter each.
 
-For more detailed information please refer to Intel SDM chapter
-"17.15 - Platform Shared Resource Control: Cache Allocation Technology".
-
 In Xen's implementation, CBM can be configured with libxl/xl interfaces but
 COS is maintained in hypervisor only. The cache partition granularity is per
 domain, each domain has COS=0 assigned by default, the corresponding CBM is
 all-ones, which means all the cache resource can be used by default.
 
+Code/Data Prioritization (CDP) Technology is an extension of CAT, which is
+available on Intel Broadwell and later server platforms. CDP enables isolation
+and separate prioritization of code and data fetches to the L3 cache in a
+software configurable manner, which can enable workload prioritization and
+tuning of cache capacity to the characteristics of the workload. CDP extends
+Cache Allocation Technology (CAT) by providing separate code and data masks
+per Class of Service (COS).
+
+CDP is disabled on the processor by default. If the CAT MSRs are used without
+enabling CDP, the processor operates in a traditional CAT-only mode.
+
+When CDP is enabled,
+
+ * the CAT mask MSRs are re-mapped into interleaved pairs of mask MSRs for
+   data or code fetches.
+
+ * the range of COS for CAT is re-indexed, with the lower-half of the COS
+   range available for CDP.
+
+CDP allows OS or Hypervisor to partition cache allocation more fine-grained,
+code cache and data cache can be specified respectively. To enable CDP on
+platform, all sockets in the platform must have CDP either enabled or
+disabled, not a mix. With CDP enabled, one COS corresponds to two CBMs (code
+CBM & data CBM), which means the number of available COS will reduce to half
+when CDP is on.
+
+For more detailed information please refer to Intel SDM chapter
+"17.16 - Platform Shared Resource Control: Cache Allocation Technology".
+
 ### xl interfaces
 
-System CAT information such as maximum COS and CBM length can be obtained by:
+System CAT information such as maximum COS, CBM length and CDP status can be
+obtained by:
 
 `xl psr-hwinfo --cat`
 
@@ -119,6 +146,13 @@ A cbm is valid only when:
 In a multi-socket system, the same cbm will be set on each socket by default.
 Per socket cbm can be specified with the `--socket SOCKET` option.
 
+To specify code CBM for the domain, `-c` or `--code` option is needed.
+
+To specify data CBM for the domain, `-d` or `--data` option is needed.
+
+If neither `-c` nor `-d` option is specified when CDP is on, the same code CBM
+and data CBM will be set for the domain.
+
 Setting the CBM may not be successful if insufficient COS is available. In
 such case unused COS(es) may be freed by setting CBM of all related domains to
 its default value(all-ones).
-- 
1.9.1


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