[PATCH v1 2/4] KVM: stats: Update doc for histogram statistics

[Jing Zhang <jingzhangos@google.com>]

Add documentations for linear and logarithmic histogram statistics.
Add binary stats capability text which is missing during merge of
the binary stats patch.

Signed-off-by: Jing Zhang <jingzhangos@google.com>
---
 Documentation/virt/kvm/api.rst | 36 +++++++++++++++++++++++++++++++---
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 3b6e3b1628b4..948d33c26704 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5171,6 +5171,9 @@ by a string of size ``name_size``.
 	#define KVM_STATS_TYPE_CUMULATIVE	(0x0 << KVM_STATS_TYPE_SHIFT)
 	#define KVM_STATS_TYPE_INSTANT		(0x1 << KVM_STATS_TYPE_SHIFT)
 	#define KVM_STATS_TYPE_PEAK		(0x2 << KVM_STATS_TYPE_SHIFT)
+	#define KVM_STATS_TYPE_LINEAR_HIST	(0x3 << KVM_STATS_TYPE_SHIFT)
+	#define KVM_STATS_TYPE_LOG_HIST		(0x4 << KVM_STATS_TYPE_SHIFT)
+	#define KVM_STATS_TYPE_MAX		KVM_STATS_TYPE_LOG_HIST
 
 	#define KVM_STATS_UNIT_SHIFT		4
 	#define KVM_STATS_UNIT_MASK		(0xF << KVM_STATS_UNIT_SHIFT)
@@ -5178,11 +5181,13 @@ by a string of size ``name_size``.
 	#define KVM_STATS_UNIT_BYTES		(0x1 << KVM_STATS_UNIT_SHIFT)
 	#define KVM_STATS_UNIT_SECONDS		(0x2 << KVM_STATS_UNIT_SHIFT)
 	#define KVM_STATS_UNIT_CYCLES		(0x3 << KVM_STATS_UNIT_SHIFT)
+	#define KVM_STATS_UNIT_MAX		KVM_STATS_UNIT_CYCLES
 
 	#define KVM_STATS_BASE_SHIFT		8
 	#define KVM_STATS_BASE_MASK		(0xF << KVM_STATS_BASE_SHIFT)
 	#define KVM_STATS_BASE_POW10		(0x0 << KVM_STATS_BASE_SHIFT)
 	#define KVM_STATS_BASE_POW2		(0x1 << KVM_STATS_BASE_SHIFT)
+	#define KVM_STATS_BASE_MAX		KVM_STATS_BASE_POW2
 
 	struct kvm_stats_desc {
 		__u32 flags;
@@ -5214,6 +5219,22 @@ Bits 0-3 of ``flags`` encode the type:
     represents a peak value for a measurement, for example the maximum number
     of items in a hash table bucket, the longest time waited and so on.
     The corresponding ``size`` field for this type is always 1.
+  * ``KVM_STATS_TYPE_LINEAR_HIST``
+    The statistics data is in the form of linear histogram. The number of
+    buckets is specified by the ``size`` field. The size of buckets is specified
+    by the ``hist_param`` field. The range of the Nth bucket (1 <= N < ``size``)
+    is [``hist_param``*(N-1), ``hist_param``*N), while the range of the last
+    bucket is [``hist_param``*(``size``-1), +INF). (+INF means positive infinity
+    value.) The bucket value indicates how many times the statistics data is in
+    the bucket's range.
+  * ``KVM_STATS_TYPE_LOG_HIST``
+    The statistics data is in the form of logarithmic histogram. The number of
+    buckets is specified by the ``size`` field. The base of logarithm is
+    specified by the ``hist_param`` field. The range of the Nth bucket (1 < N <
+    ``size``) is [pow(``hist_param``, N-2), pow(``hist_param``, N-1)). The range
+    of the first bucket is [0, 1), while the range of the last bucket is
+    [pow(``hist_param``, ``size``-2), +INF). The bucket value indicates how many
+    times the statistics data is in the bucket's range.
 
 Bits 4-7 of ``flags`` encode the unit:
   * ``KVM_STATS_UNIT_NONE``
@@ -5246,9 +5267,10 @@ unsigned 64bit data.
 The ``offset`` field is the offset from the start of Data Block to the start of
 the corresponding statistics data.
 
-The ``unused`` field is reserved for future support for other types of
-statistics data, like log/linear histogram. Its value is always 0 for the types
-defined above.
+The ``hist_param`` field is used as a parameter for histogram statistics data.
+For linear histogram statistics data, it indicates the size of a bucket. For
+logarithmic histogram statistics data, it indicates the base of the logarithm.
+Only base of 2 is supported fo logarithmic histogram.
 
 The ``name`` field is the name string of the statistics data. The name string
 starts at the end of ``struct kvm_stats_desc``.  The maximum length including
@@ -7182,3 +7204,11 @@ The argument to KVM_ENABLE_CAP is also a bitmask, and must be a subset
 of the result of KVM_CHECK_EXTENSION.  KVM will forward to userspace
 the hypercalls whose corresponding bit is in the argument, and return
 ENOSYS for the others.
+
+8.35 KVM_CAP_STATS_BINARY_FD
+----------------------------
+
+:Architectures: all
+
+This capability indicates the feature that userspace can get a file descriptor
+for every VM and VCPU to read statistics data in binary format.
-- 
2.32.0.93.g670b81a890-goog