[GIT pull] x86/cache updates for 4.18

From: Thomas Gleixner
Date: Mon Jun 04 2018 - 06:40:19 EST

Linus,

please pull the latest x86-cache-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-cache-for-linus

An update for the Intel Resource Director Technolgy (RDT) which adds a
feedback driven software controller to runtime adjust the bandwidth
allocation MSRs. This makes the allocations more accurate and allows to use
bandwidth values in understandable units (MB/s) instead of using percentage
based allocations as the original, still available, interface. The software
controller can be enabled with a new mount option for the resctrl
filesystem.

Thanks,

tglx

------------------>
Vikas Shivappa (6):
x86/intel_rdt/mba_sc: Documentation for MBA software controller(mba_sc)
x86/intel_rdt/mba_sc: Enable/disable MBA software controller
x86/intel_rdt/mba_sc: Add initialization support
x86/intel_rdt/mba_sc: Add schemata support
x86/intel_rdt/mba_sc: Prepare for feedback loop
x86/intel_rdt/mba_sc: Feedback loop to dynamically update mem bandwidth


Documentation/x86/intel_rdt_ui.txt | 75 ++++++++++--
arch/x86/kernel/cpu/intel_rdt.c | 50 +++++---
arch/x86/kernel/cpu/intel_rdt.h | 18 +++
arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c | 24 +++-
arch/x86/kernel/cpu/intel_rdt_monitor.c | 170 ++++++++++++++++++++++++++--
arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 33 ++++++
6 files changed, 337 insertions(+), 33 deletions(-)

diff --git a/Documentation/x86/intel_rdt_ui.txt b/Documentation/x86/intel_rdt_ui.txt
index 71c30984e94d..a16aa2113840 100644
--- a/Documentation/x86/intel_rdt_ui.txt
+++ b/Documentation/x86/intel_rdt_ui.txt
@@ -17,12 +17,14 @@ MBA (Memory Bandwidth Allocation) - "mba"

To use the feature mount the file system:

- # mount -t resctrl resctrl [-o cdp[,cdpl2]] /sys/fs/resctrl
+ # mount -t resctrl resctrl [-o cdp[,cdpl2][,mba_MBps]] /sys/fs/resctrl

mount options are:

"cdp": Enable code/data prioritization in L3 cache allocations.
"cdpl2": Enable code/data prioritization in L2 cache allocations.
+"mba_MBps": Enable the MBA Software Controller(mba_sc) to specify MBA
+ bandwidth in MBps

L2 and L3 CDP are controlled seperately.

@@ -270,10 +272,11 @@ and 0xA are not. On a system with a 20-bit mask each bit represents 5%
of the capacity of the cache. You could partition the cache into four
equal parts with masks: 0x1f, 0x3e0, 0x7c00, 0xf8000.

-Memory bandwidth(b/w) percentage
---------------------------------
-For Memory b/w resource, user controls the resource by indicating the
-percentage of total memory b/w.
+Memory bandwidth Allocation and monitoring
+------------------------------------------
+
+For Memory bandwidth resource, by default the user controls the resource
+by indicating the percentage of total memory bandwidth.

The minimum bandwidth percentage value for each cpu model is predefined
and can be looked up through "info/MB/min_bandwidth". The bandwidth
@@ -285,7 +288,47 @@ to the next control step available on the hardware.
The bandwidth throttling is a core specific mechanism on some of Intel
SKUs. Using a high bandwidth and a low bandwidth setting on two threads
sharing a core will result in both threads being throttled to use the
-low bandwidth.
+low bandwidth. The fact that Memory bandwidth allocation(MBA) is a core
+specific mechanism where as memory bandwidth monitoring(MBM) is done at
+the package level may lead to confusion when users try to apply control
+via the MBA and then monitor the bandwidth to see if the controls are
+effective. Below are such scenarios:
+
+1. User may *not* see increase in actual bandwidth when percentage
+ values are increased:
+
+This can occur when aggregate L2 external bandwidth is more than L3
+external bandwidth. Consider an SKL SKU with 24 cores on a package and
+where L2 external is 10GBps (hence aggregate L2 external bandwidth is
+240GBps) and L3 external bandwidth is 100GBps. Now a workload with '20
+threads, having 50% bandwidth, each consuming 5GBps' consumes the max L3
+bandwidth of 100GBps although the percentage value specified is only 50%
+<< 100%. Hence increasing the bandwidth percentage will not yeild any
+more bandwidth. This is because although the L2 external bandwidth still
+has capacity, the L3 external bandwidth is fully used. Also note that
+this would be dependent on number of cores the benchmark is run on.
+
+2. Same bandwidth percentage may mean different actual bandwidth
+ depending on # of threads:
+
+For the same SKU in #1, a 'single thread, with 10% bandwidth' and '4
+thread, with 10% bandwidth' can consume upto 10GBps and 40GBps although
+they have same percentage bandwidth of 10%. This is simply because as
+threads start using more cores in an rdtgroup, the actual bandwidth may
+increase or vary although user specified bandwidth percentage is same.
+
+In order to mitigate this and make the interface more user friendly,
+resctrl added support for specifying the bandwidth in MBps as well. The
+kernel underneath would use a software feedback mechanism or a "Software
+Controller(mba_sc)" which reads the actual bandwidth using MBM counters
+and adjust the memowy bandwidth percentages to ensure
+
+ "actual bandwidth < user specified bandwidth".
+
+By default, the schemata would take the bandwidth percentage values
+where as user can switch to the "MBA software controller" mode using
+a mount option 'mba_MBps'. The schemata format is specified in the below
+sections.

L3 schemata file details (code and data prioritization disabled)
----------------------------------------------------------------
@@ -308,13 +351,20 @@ schemata format is always:

L2:<cache_id0>=<cbm>;<cache_id1>=<cbm>;...

-Memory b/w Allocation details
------------------------------
+Memory bandwidth Allocation (default mode)
+------------------------------------------

Memory b/w domain is L3 cache.

MB:<cache_id0>=bandwidth0;<cache_id1>=bandwidth1;...

+Memory bandwidth Allocation specified in MBps
+---------------------------------------------
+
+Memory bandwidth domain is L3 cache.
+
+ MB:<cache_id0>=bw_MBps0;<cache_id1>=bw_MBps1;...
+
Reading/writing the schemata file
---------------------------------
Reading the schemata file will show the state of all resources
@@ -358,6 +408,15 @@ allocations can overlap or not. The allocations specifies the maximum
b/w that the group may be able to use and the system admin can configure
the b/w accordingly.

+If the MBA is specified in MB(megabytes) then user can enter the max b/w in MB
+rather than the percentage values.
+
+# echo "L3:0=3;1=c\nMB:0=1024;1=500" > /sys/fs/resctrl/p0/schemata
+# echo "L3:0=3;1=3\nMB:0=1024;1=500" > /sys/fs/resctrl/p1/schemata
+
+In the above example the tasks in "p1" and "p0" on socket 0 would use a max b/w
+of 1024MB where as on socket 1 they would use 500MB.
+
Example 2
---------
Again two sockets, but this time with a more realistic 20-bit mask.
diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
index 589b948e6e01..24bfa63e86cf 100644
--- a/arch/x86/kernel/cpu/intel_rdt.c
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -33,8 +33,8 @@
#include <asm/intel_rdt_sched.h>
#include "intel_rdt.h"

-#define MAX_MBA_BW 100u
#define MBA_IS_LINEAR 0x4
+#define MBA_MAX_MBPS U32_MAX

/* Mutex to protect rdtgroup access. */
DEFINE_MUTEX(rdtgroup_mutex);
@@ -178,7 +178,7 @@ struct rdt_resource rdt_resources_all[] = {
.msr_update = mba_wrmsr,
.cache_level = 3,
.parse_ctrlval = parse_bw,
- .format_str = "%d=%*d",
+ .format_str = "%d=%*u",
.fflags = RFTYPE_RES_MB,
},
};
@@ -230,6 +230,14 @@ static inline void cache_alloc_hsw_probe(void)
rdt_alloc_capable = true;
}

+bool is_mba_sc(struct rdt_resource *r)
+{
+ if (!r)
+ return rdt_resources_all[RDT_RESOURCE_MBA].membw.mba_sc;
+
+ return r->membw.mba_sc;
+}
+
/*
* rdt_get_mb_table() - get a mapping of bandwidth(b/w) percentage values
* exposed to user interface and the h/w understandable delay values.
@@ -341,7 +349,7 @@ static int get_cache_id(int cpu, int level)
* that can be written to QOS_MSRs.
* There are currently no SKUs which support non linear delay values.
*/
-static u32 delay_bw_map(unsigned long bw, struct rdt_resource *r)
+u32 delay_bw_map(unsigned long bw, struct rdt_resource *r)
{
if (r->membw.delay_linear)
return MAX_MBA_BW - bw;
@@ -431,25 +439,40 @@ struct rdt_domain *rdt_find_domain(struct rdt_resource *r, int id,
return NULL;
}

+void setup_default_ctrlval(struct rdt_resource *r, u32 *dc, u32 *dm)
+{
+ int i;
+
+ /*
+ * Initialize the Control MSRs to having no control.
+ * For Cache Allocation: Set all bits in cbm
+ * For Memory Allocation: Set b/w requested to 100%
+ * and the bandwidth in MBps to U32_MAX
+ */
+ for (i = 0; i < r->num_closid; i++, dc++, dm++) {
+ *dc = r->default_ctrl;
+ *dm = MBA_MAX_MBPS;
+ }
+}
+
static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d)
{
struct msr_param m;
- u32 *dc;
- int i;
+ u32 *dc, *dm;

dc = kmalloc_array(r->num_closid, sizeof(*d->ctrl_val), GFP_KERNEL);
if (!dc)
return -ENOMEM;

- d->ctrl_val = dc;
+ dm = kmalloc_array(r->num_closid, sizeof(*d->mbps_val), GFP_KERNEL);
+ if (!dm) {
+ kfree(dc);
+ return -ENOMEM;
+ }

- /*
- * Initialize the Control MSRs to having no control.
- * For Cache Allocation: Set all bits in cbm
- * For Memory Allocation: Set b/w requested to 100
- */
- for (i = 0; i < r->num_closid; i++, dc++)
- *dc = r->default_ctrl;
+ d->ctrl_val = dc;
+ d->mbps_val = dm;
+ setup_default_ctrlval(r, dc, dm);

m.low = 0;
m.high = r->num_closid;
@@ -588,6 +611,7 @@ static void domain_remove_cpu(int cpu, struct rdt_resource *r)
}

kfree(d->ctrl_val);
+ kfree(d->mbps_val);
kfree(d->rmid_busy_llc);
kfree(d->mbm_total);
kfree(d->mbm_local);
diff --git a/arch/x86/kernel/cpu/intel_rdt.h b/arch/x86/kernel/cpu/intel_rdt.h
index 3fd7a70ee04a..39752825e376 100644
--- a/arch/x86/kernel/cpu/intel_rdt.h
+++ b/arch/x86/kernel/cpu/intel_rdt.h
@@ -28,6 +28,7 @@

#define MBM_CNTR_WIDTH 24
#define MBM_OVERFLOW_INTERVAL 1000
+#define MAX_MBA_BW 100u

#define RMID_VAL_ERROR BIT_ULL(63)
#define RMID_VAL_UNAVAIL BIT_ULL(62)
@@ -180,10 +181,20 @@ struct rftype {
* struct mbm_state - status for each MBM counter in each domain
* @chunks: Total data moved (multiply by rdt_group.mon_scale to get bytes)
* @prev_msr Value of IA32_QM_CTR for this RMID last time we read it
+ * @chunks_bw Total local data moved. Used for bandwidth calculation
+ * @prev_bw_msr:Value of previous IA32_QM_CTR for bandwidth counting
+ * @prev_bw The most recent bandwidth in MBps
+ * @delta_bw Difference between the current and previous bandwidth
+ * @delta_comp Indicates whether to compute the delta_bw
*/
struct mbm_state {
u64 chunks;
u64 prev_msr;
+ u64 chunks_bw;
+ u64 prev_bw_msr;
+ u32 prev_bw;
+ u32 delta_bw;
+ bool delta_comp;
};

/**
@@ -202,6 +213,7 @@ struct mbm_state {
* @cqm_work_cpu:
* worker cpu for CQM h/w counters
* @ctrl_val: array of cache or mem ctrl values (indexed by CLOSID)
+ * @mbps_val: When mba_sc is enabled, this holds the bandwidth in MBps
* @new_ctrl: new ctrl value to be loaded
* @have_new_ctrl: did user provide new_ctrl for this domain
*/
@@ -217,6 +229,7 @@ struct rdt_domain {
int mbm_work_cpu;
int cqm_work_cpu;
u32 *ctrl_val;
+ u32 *mbps_val;
u32 new_ctrl;
bool have_new_ctrl;
};
@@ -259,6 +272,7 @@ struct rdt_cache {
* @min_bw: Minimum memory bandwidth percentage user can request
* @bw_gran: Granularity at which the memory bandwidth is allocated
* @delay_linear: True if memory B/W delay is in linear scale
+ * @mba_sc: True if MBA software controller(mba_sc) is enabled
* @mb_map: Mapping of memory B/W percentage to memory B/W delay
*/
struct rdt_membw {
@@ -266,6 +280,7 @@ struct rdt_membw {
u32 min_bw;
u32 bw_gran;
u32 delay_linear;
+ bool mba_sc;
u32 *mb_map;
};

@@ -445,6 +460,9 @@ void mon_event_read(struct rmid_read *rr, struct rdt_domain *d,
void mbm_setup_overflow_handler(struct rdt_domain *dom,
unsigned long delay_ms);
void mbm_handle_overflow(struct work_struct *work);
+bool is_mba_sc(struct rdt_resource *r);
+void setup_default_ctrlval(struct rdt_resource *r, u32 *dc, u32 *dm);
+u32 delay_bw_map(unsigned long bw, struct rdt_resource *r);
void cqm_setup_limbo_handler(struct rdt_domain *dom, unsigned long delay_ms);
void cqm_handle_limbo(struct work_struct *work);
bool has_busy_rmid(struct rdt_resource *r, struct rdt_domain *d);
diff --git a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
index 23e1d5c249c6..116d57b248d3 100644
--- a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
+++ b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
@@ -53,7 +53,8 @@ static bool bw_validate(char *buf, unsigned long *data, struct rdt_resource *r)
return false;
}

- if (bw < r->membw.min_bw || bw > r->default_ctrl) {
+ if ((bw < r->membw.min_bw || bw > r->default_ctrl) &&
+ !is_mba_sc(r)) {
rdt_last_cmd_printf("MB value %ld out of range [%d,%d]\n", bw,
r->membw.min_bw, r->default_ctrl);
return false;
@@ -179,6 +180,8 @@ static int update_domains(struct rdt_resource *r, int closid)
struct msr_param msr_param;
cpumask_var_t cpu_mask;
struct rdt_domain *d;
+ bool mba_sc;
+ u32 *dc;
int cpu;

if (!zalloc_cpumask_var(&cpu_mask, GFP_KERNEL))
@@ -188,13 +191,20 @@ static int update_domains(struct rdt_resource *r, int closid)
msr_param.high = msr_param.low + 1;
msr_param.res = r;

+ mba_sc = is_mba_sc(r);
list_for_each_entry(d, &r->domains, list) {
- if (d->have_new_ctrl && d->new_ctrl != d->ctrl_val[closid]) {
+ dc = !mba_sc ? d->ctrl_val : d->mbps_val;
+ if (d->have_new_ctrl && d->new_ctrl != dc[closid]) {
cpumask_set_cpu(cpumask_any(&d->cpu_mask), cpu_mask);
- d->ctrl_val[closid] = d->new_ctrl;
+ dc[closid] = d->new_ctrl;
}
}
- if (cpumask_empty(cpu_mask))
+
+ /*
+ * Avoid writing the control msr with control values when
+ * MBA software controller is enabled
+ */
+ if (cpumask_empty(cpu_mask) || mba_sc)
goto done;
cpu = get_cpu();
/* Update CBM on this cpu if it's in cpu_mask. */
@@ -282,13 +292,17 @@ static void show_doms(struct seq_file *s, struct rdt_resource *r, int closid)
{
struct rdt_domain *dom;
bool sep = false;
+ u32 ctrl_val;

seq_printf(s, "%*s:", max_name_width, r->name);
list_for_each_entry(dom, &r->domains, list) {
if (sep)
seq_puts(s, ";");
+
+ ctrl_val = (!is_mba_sc(r) ? dom->ctrl_val[closid] :
+ dom->mbps_val[closid]);
seq_printf(s, r->format_str, dom->id, max_data_width,
- dom->ctrl_val[closid]);
+ ctrl_val);
sep = true;
}
seq_puts(s, "\n");
diff --git a/arch/x86/kernel/cpu/intel_rdt_monitor.c b/arch/x86/kernel/cpu/intel_rdt_monitor.c
index 681450eee428..b0f3aed76b75 100644
--- a/arch/x86/kernel/cpu/intel_rdt_monitor.c
+++ b/arch/x86/kernel/cpu/intel_rdt_monitor.c
@@ -225,10 +225,18 @@ void free_rmid(u32 rmid)
list_add_tail(&entry->list, &rmid_free_lru);
}

+static u64 mbm_overflow_count(u64 prev_msr, u64 cur_msr)
+{
+ u64 shift = 64 - MBM_CNTR_WIDTH, chunks;
+
+ chunks = (cur_msr << shift) - (prev_msr << shift);
+ return chunks >>= shift;
+}
+
static int __mon_event_count(u32 rmid, struct rmid_read *rr)
{
- u64 chunks, shift, tval;
struct mbm_state *m;
+ u64 chunks, tval;

tval = __rmid_read(rmid, rr->evtid);
if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL)) {
@@ -254,14 +262,12 @@ static int __mon_event_count(u32 rmid, struct rmid_read *rr)
}

if (rr->first) {
- m->prev_msr = tval;
- m->chunks = 0;
+ memset(m, 0, sizeof(struct mbm_state));
+ m->prev_bw_msr = m->prev_msr = tval;
return 0;
}

- shift = 64 - MBM_CNTR_WIDTH;
- chunks = (tval << shift) - (m->prev_msr << shift);
- chunks >>= shift;
+ chunks = mbm_overflow_count(m->prev_msr, tval);
m->chunks += chunks;
m->prev_msr = tval;

@@ -269,6 +275,32 @@ static int __mon_event_count(u32 rmid, struct rmid_read *rr)
return 0;
}

+/*
+ * Supporting function to calculate the memory bandwidth
+ * and delta bandwidth in MBps.
+ */
+static void mbm_bw_count(u32 rmid, struct rmid_read *rr)
+{
+ struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3];
+ struct mbm_state *m = &rr->d->mbm_local[rmid];
+ u64 tval, cur_bw, chunks;
+
+ tval = __rmid_read(rmid, rr->evtid);
+ if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL))
+ return;
+
+ chunks = mbm_overflow_count(m->prev_bw_msr, tval);
+ m->chunks_bw += chunks;
+ m->chunks = m->chunks_bw;
+ cur_bw = (chunks * r->mon_scale) >> 20;
+
+ if (m->delta_comp)
+ m->delta_bw = abs(cur_bw - m->prev_bw);
+ m->delta_comp = false;
+ m->prev_bw = cur_bw;
+ m->prev_bw_msr = tval;
+}
+
/*
* This is called via IPI to read the CQM/MBM counters
* on a domain.
@@ -297,6 +329,118 @@ void mon_event_count(void *info)
}
}

+/*
+ * Feedback loop for MBA software controller (mba_sc)
+ *
+ * mba_sc is a feedback loop where we periodically read MBM counters and
+ * adjust the bandwidth percentage values via the IA32_MBA_THRTL_MSRs so
+ * that:
+ *
+ * current bandwdith(cur_bw) < user specified bandwidth(user_bw)
+ *
+ * This uses the MBM counters to measure the bandwidth and MBA throttle
+ * MSRs to control the bandwidth for a particular rdtgrp. It builds on the
+ * fact that resctrl rdtgroups have both monitoring and control.
+ *
+ * The frequency of the checks is 1s and we just tag along the MBM overflow
+ * timer. Having 1s interval makes the calculation of bandwidth simpler.
+ *
+ * Although MBA's goal is to restrict the bandwidth to a maximum, there may
+ * be a need to increase the bandwidth to avoid uncecessarily restricting
+ * the L2 <-> L3 traffic.
+ *
+ * Since MBA controls the L2 external bandwidth where as MBM measures the
+ * L3 external bandwidth the following sequence could lead to such a
+ * situation.
+ *
+ * Consider an rdtgroup which had high L3 <-> memory traffic in initial
+ * phases -> mba_sc kicks in and reduced bandwidth percentage values -> but
+ * after some time rdtgroup has mostly L2 <-> L3 traffic.
+ *
+ * In this case we may restrict the rdtgroup's L2 <-> L3 traffic as its
+ * throttle MSRs already have low percentage values. To avoid
+ * unnecessarily restricting such rdtgroups, we also increase the bandwidth.
+ */
+static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_domain *dom_mbm)
+{
+ u32 closid, rmid, cur_msr, cur_msr_val, new_msr_val;
+ struct mbm_state *pmbm_data, *cmbm_data;
+ u32 cur_bw, delta_bw, user_bw;
+ struct rdt_resource *r_mba;
+ struct rdt_domain *dom_mba;
+ struct list_head *head;
+ struct rdtgroup *entry;
+
+ r_mba = &rdt_resources_all[RDT_RESOURCE_MBA];
+ closid = rgrp->closid;
+ rmid = rgrp->mon.rmid;
+ pmbm_data = &dom_mbm->mbm_local[rmid];
+
+ dom_mba = get_domain_from_cpu(smp_processor_id(), r_mba);
+ if (!dom_mba) {
+ pr_warn_once("Failure to get domain for MBA update\n");
+ return;
+ }
+
+ cur_bw = pmbm_data->prev_bw;
+ user_bw = dom_mba->mbps_val[closid];
+ delta_bw = pmbm_data->delta_bw;
+ cur_msr_val = dom_mba->ctrl_val[closid];
+
+ /*
+ * For Ctrl groups read data from child monitor groups.
+ */
+ head = &rgrp->mon.crdtgrp_list;
+ list_for_each_entry(entry, head, mon.crdtgrp_list) {
+ cmbm_data = &dom_mbm->mbm_local[entry->mon.rmid];
+ cur_bw += cmbm_data->prev_bw;
+ delta_bw += cmbm_data->delta_bw;
+ }
+
+ /*
+ * Scale up/down the bandwidth linearly for the ctrl group. The
+ * bandwidth step is the bandwidth granularity specified by the
+ * hardware.
+ *
+ * The delta_bw is used when increasing the bandwidth so that we
+ * dont alternately increase and decrease the control values
+ * continuously.
+ *
+ * For ex: consider cur_bw = 90MBps, user_bw = 100MBps and if
+ * bandwidth step is 20MBps(> user_bw - cur_bw), we would keep
+ * switching between 90 and 110 continuously if we only check
+ * cur_bw < user_bw.
+ */
+ if (cur_msr_val > r_mba->membw.min_bw && user_bw < cur_bw) {
+ new_msr_val = cur_msr_val - r_mba->membw.bw_gran;
+ } else if (cur_msr_val < MAX_MBA_BW &&
+ (user_bw > (cur_bw + delta_bw))) {
+ new_msr_val = cur_msr_val + r_mba->membw.bw_gran;
+ } else {
+ return;
+ }
+
+ cur_msr = r_mba->msr_base + closid;
+ wrmsrl(cur_msr, delay_bw_map(new_msr_val, r_mba));
+ dom_mba->ctrl_val[closid] = new_msr_val;
+
+ /*
+ * Delta values are updated dynamically package wise for each
+ * rdtgrp everytime the throttle MSR changes value.
+ *
+ * This is because (1)the increase in bandwidth is not perfectly
+ * linear and only "approximately" linear even when the hardware
+ * says it is linear.(2)Also since MBA is a core specific
+ * mechanism, the delta values vary based on number of cores used
+ * by the rdtgrp.
+ */
+ pmbm_data->delta_comp = true;
+ list_for_each_entry(entry, head, mon.crdtgrp_list) {
+ cmbm_data = &dom_mbm->mbm_local[entry->mon.rmid];
+ cmbm_data->delta_comp = true;
+ }
+}
+
static void mbm_update(struct rdt_domain *d, int rmid)
{
struct rmid_read rr;
@@ -314,7 +458,16 @@ static void mbm_update(struct rdt_domain *d, int rmid)
}
if (is_mbm_local_enabled()) {
rr.evtid = QOS_L3_MBM_LOCAL_EVENT_ID;
- __mon_event_count(rmid, &rr);
+
+ /*
+ * Call the MBA software controller only for the
+ * control groups and when user has enabled
+ * the software controller explicitly.
+ */
+ if (!is_mba_sc(NULL))
+ __mon_event_count(rmid, &rr);
+ else
+ mbm_bw_count(rmid, &rr);
}
}

@@ -385,6 +538,9 @@ void mbm_handle_overflow(struct work_struct *work)
head = &prgrp->mon.crdtgrp_list;
list_for_each_entry(crgrp, head, mon.crdtgrp_list)
mbm_update(d, crgrp->mon.rmid);
+
+ if (is_mba_sc(NULL))
+ update_mba_bw(prgrp, d);
}

schedule_delayed_work_on(cpu, &d->mbm_over, delay);
diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index fca759d272a1..749856a2e736 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -1005,6 +1005,11 @@ static void l2_qos_cfg_update(void *arg)
wrmsrl(IA32_L2_QOS_CFG, *enable ? L2_QOS_CDP_ENABLE : 0ULL);
}

+static inline bool is_mba_linear(void)
+{
+ return rdt_resources_all[RDT_RESOURCE_MBA].membw.delay_linear;
+}
+
static int set_cache_qos_cfg(int level, bool enable)
{
void (*update)(void *arg);
@@ -1041,6 +1046,28 @@ static int set_cache_qos_cfg(int level, bool enable)
return 0;
}

+/*
+ * Enable or disable the MBA software controller
+ * which helps user specify bandwidth in MBps.
+ * MBA software controller is supported only if
+ * MBM is supported and MBA is in linear scale.
+ */
+static int set_mba_sc(bool mba_sc)
+{
+ struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA];
+ struct rdt_domain *d;
+
+ if (!is_mbm_enabled() || !is_mba_linear() ||
+ mba_sc == is_mba_sc(r))
+ return -EINVAL;
+
+ r->membw.mba_sc = mba_sc;
+ list_for_each_entry(d, &r->domains, list)
+ setup_default_ctrlval(r, d->ctrl_val, d->mbps_val);
+
+ return 0;
+}
+
static int cdp_enable(int level, int data_type, int code_type)
{
struct rdt_resource *r_ldata = &rdt_resources_all[data_type];
@@ -1123,6 +1150,10 @@ static int parse_rdtgroupfs_options(char *data)
ret = cdpl2_enable();
if (ret)
goto out;
+ } else if (!strcmp(token, "mba_MBps")) {
+ ret = set_mba_sc(true);
+ if (ret)
+ goto out;
} else {
ret = -EINVAL;
goto out;
@@ -1445,6 +1476,8 @@ static void rdt_kill_sb(struct super_block *sb)
cpus_read_lock();
mutex_lock(&rdtgroup_mutex);

+ set_mba_sc(false);
+
/*Put everything back to default values. */
for_each_alloc_enabled_rdt_resource(r)
reset_all_ctrls(r);