linux-kernel - [RFC PATCH 15/20] x86/intel_rdt: Prevent new allocations from pseudo-locked regions

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Date:   Mon, 13 Nov 2017 08:39:38 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     tglx@...utronix.de, fenghua.yu@...el.com, tony.luck@...el.com
Cc:     vikas.shivappa@...ux.intel.com, dave.hansen@...el.com,
        mingo@...hat.com, hpa@...or.com, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Reinette Chatre <reinette.chatre@...el.com>
Subject: [RFC PATCH 15/20] x86/intel_rdt: Prevent new allocations from pseudo-locked regions

When a user requests a new cache allocation we need to enforce that it
does not intersect with an existing pseudo-locked region. An allocation
with a bitmask intersection with a pseudo-locked region will enable
cache allocations to that region and thus evict pseudo-locked data.

Signed-off-by: Reinette Chatre <reinette.chatre@...el.com>
---
 arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
index 50d3743ed79e..fb3ecc864b2a 100644
--- a/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
+++ b/arch/x86/kernel/cpu/intel_rdt_ctrlmondata.c
@@ -136,8 +136,10 @@ static bool cbm_validate(char *buf, unsigned long *data, struct rdt_resource *r)
 }
 
 /*
- * Read one cache bit mask (hex). Check that it is valid for the current
- * resource type.
+ * Read one cache bit mask (hex). Check that it is valid and available for
+ * the current resource type. While CAT allows CBM to overlap amongst
+ * classes of service we do not allow a CBM to overlap with a region that has
+ * been pseudo-locked.
  */
 int parse_cbm(char *buf, struct rdt_resource *r, struct rdt_domain *d)
 {
@@ -150,6 +152,8 @@ int parse_cbm(char *buf, struct rdt_resource *r, struct rdt_domain *d)
 
 	if(!cbm_validate(buf, &data, r))
 		return -EINVAL;
+	if (cbm_pseudo_locked(data, d))
+		return -EINVAL;
 	d->new_ctrl = data;
 	d->have_new_ctrl = true;
 
-- 
2.13.5