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From: Fenghua Yu <fenghua.yu@intel.com>
To: "Thomas Gleixner" <tglx@linutronix.de>,
	"Ingo Molnar" <mingo@redhat.com>, "H Peter Anvin" <hpa@zytor.com>,
	"Tony Luck" <tony.luck@intel.com>
Cc: "Chatre, Reinette" <reinette.chatre@intel.com>,
	"Xiaochen Shen" <xiaochen.shen@intel.com>,
	"Chen Yu" <yu.c.chen@intel.com>,
	"linux-kernel" <linux-kernel@vger.kernel.org>,
	"x86" <x86@kernel.org>, "Fenghua Yu" <fenghua.yu@intel.com>
Subject: [PATCH V2 2/9] x86/intel_rdt: Fix size reporting of MBA resource
Date: Sat, 15 Sep 2018 14:58:20 -0700	[thread overview]
Message-ID: <1537048707-76280-3-git-send-email-fenghua.yu@intel.com> (raw)
In-Reply-To: <1537048707-76280-1-git-send-email-fenghua.yu@intel.com>

From: Reinette Chatre <reinette.chatre@intel.com>

Chen Yu reported a divide-by-zero error when accessing the 'size'
resctrl file when a MBA resource is enabled.

divide error: 0000 [#1] SMP PTI
CPU: 93 PID: 1929 Comm: cat Not tainted 4.19.0-rc2-debug-rdt+ #25
RIP: 0010:rdtgroup_cbm_to_size+0x7e/0xa0
Call Trace:
rdtgroup_size_show+0x11a/0x1d0
seq_read+0xd8/0x3b0

Quoting Chen Yu's report: This is because for MB resource,
the r->cache.cbm_len is zero, thus calculating size in
rdtgroup_cbm_to_size() will trigger the exception.

Fix this issue in the 'size' file by getting correct memory bandwidth
value which is in MBps when MBA software controller is enabled or in
percentage when MBA software controller is disabled.

Fixes: d9b48c86eb38 ("x86/intel_rdt: Display resource groups' allocations in bytes")
Link: https://lkml.kernel.org/r/20180904174614.26682-1-yu.c.chen@intel.com
Reported-by: Chen Yu <yu.c.chen@intel.com>
Tested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
---
 arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index b799c00bef09..32e8bbdf2400 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -1155,8 +1155,8 @@ static int rdtgroup_size_show(struct kernfs_open_file *of,
 	struct rdt_resource *r;
 	struct rdt_domain *d;
 	unsigned int size;
-	bool sep = false;
-	u32 cbm;
+	bool sep;
+	u32 ctrl;
 
 	rdtgrp = rdtgroup_kn_lock_live(of->kn);
 	if (!rdtgrp) {
@@ -1174,6 +1174,7 @@ static int rdtgroup_size_show(struct kernfs_open_file *of,
 	}
 
 	for_each_alloc_enabled_rdt_resource(r) {
+		sep = false;
 		seq_printf(s, "%*s:", max_name_width, r->name);
 		list_for_each_entry(d, &r->domains, list) {
 			if (sep)
@@ -1181,8 +1182,13 @@ static int rdtgroup_size_show(struct kernfs_open_file *of,
 			if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
 				size = 0;
 			} else {
-				cbm = d->ctrl_val[rdtgrp->closid];
-				size = rdtgroup_cbm_to_size(r, d, cbm);
+				ctrl = (!is_mba_sc(r) ?
+						d->ctrl_val[rdtgrp->closid] :
+						d->mbps_val[rdtgrp->closid]);
+				if (r->rid == RDT_RESOURCE_MBA)
+					size = ctrl;
+				else
+					size = rdtgroup_cbm_to_size(r, d, ctrl);
 			}
 			seq_printf(s, "%d=%u", d->id, size);
 			sep = true;
-- 
2.19.0


  parent reply	other threads:[~2018-09-15 22:02 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-15 21:58 [PATCH V2 0/9] x86/intel_rdt: MBA integration fixes Fenghua Yu
2018-09-15 21:58 ` [PATCH V2 1/9] x86/intel_rdt: Fix data type in parsing callbacks Fenghua Yu
2018-09-18 21:42   ` [tip:x86/urgent] " tip-bot for Xiaochen Shen
2018-09-15 21:58 ` Fenghua Yu [this message]
2018-09-18 21:43   ` [tip:x86/urgent] x86/intel_rdt: Fix size reporting of MBA resource tip-bot for Reinette Chatre
2018-09-15 21:58 ` [PATCH V2 3/9] x86/intel_rdt: Global closid helper to support future fixes Fenghua Yu
2018-09-18 21:43   ` [tip:x86/urgent] " tip-bot for Reinette Chatre
2018-09-15 21:58 ` [PATCH V2 4/9] x86/intel_rdt: Fix invalid mode warning when multiple resources are managed Fenghua Yu
2018-09-18 21:44   ` [tip:x86/urgent] " tip-bot for Reinette Chatre
2018-09-15 21:58 ` [PATCH V2 5/9] x86/intel_rdt: Fix unchecked MSR access Fenghua Yu
2018-09-18 21:45   ` [tip:x86/urgent] " tip-bot for Reinette Chatre
2018-09-15 21:58 ` [PATCH V2 6/9] x86/intel_rdt: Do not allow pseudo-locking of MBA resource Fenghua Yu
2018-09-18 21:45   ` [tip:x86/urgent] " tip-bot for Reinette Chatre
2018-09-15 21:58 ` [PATCH V2 7/9] x86/intel_rdt: Fix incorrect loop end condition Fenghua Yu
2018-09-18 21:46   ` [tip:x86/urgent] " tip-bot for Reinette Chatre
2018-09-15 21:58 ` [PATCH V2 8/9] x86/intel_rdt: Fix exclusive mode handling of MBA resource Fenghua Yu
2018-09-18 21:46   ` [tip:x86/urgent] " tip-bot for Reinette Chatre
2018-09-15 21:58 ` [PATCH V2 9/9] x86/intel_rdt: Fix incorrect loop end condition Fenghua Yu
2018-09-18 21:47   ` [tip:x86/urgent] " tip-bot for Reinette Chatre
  -- strict thread matches above, loose matches on Subject: below --
2018-09-04 17:46 [PATCH][RFC] x86/intel_rdt: Do not display size for non-CAT resource Chen Yu
2018-09-04 20:24 ` Reinette Chatre
2018-09-04 22:36   ` Reinette Chatre
2018-09-05  6:28     ` Yu Chen
2018-09-05 20:52       ` Reinette Chatre

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