[PATCH v2 3/7] EDAC/intel-bff: Add stub Intel bitfix filter driver

[Tony Luck]

Check if the platform supports threshold based cache error reporting and
the bitfix filter reset feature.

Co-developed-by: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>
Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
 drivers/edac/intel-bff.c | 54 ++++++++++++++++++++++++++++++++++++++++
 MAINTAINERS              |  6 +++++
 drivers/edac/Kconfig     | 13 ++++++++++
 drivers/edac/Makefile    |  2 ++
 4 files changed, 75 insertions(+)
 create mode 100644 drivers/edac/intel-bff.c

diff --git a/drivers/edac/intel-bff.c b/drivers/edac/intel-bff.c
new file mode 100644
index 000000000000..905cbe58bc53
--- /dev/null
+++ b/drivers/edac/intel-bff.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2026 Intel Corporation. */
+
+/*
+ * Intel driver to reset bitfix filters when they overflow.
+ *
+ * Each bitfix filter has limited slots to track corrected errors.
+ * These slots can be filled by transient corrected errors (e.g.,
+ * bit flips from particle strikes) that don't represent permanent
+ * hardware defects.
+ *
+ * When the filter overflows (yellow status), reset it to reclaim
+ * slots occupied by transient corrected errors. If the overflow
+ * repeats frequently after reset, it indicates persistent hardware
+ * defects that need attention: the system should be scheduled for
+ * servicing.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/cpufeature.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include <asm/cpufeatures.h>
+#include <asm/mce.h>
+#include <asm/msr.h>
+#include <asm/msr-index.h>
+
+static int __init bff_init(void)
+{
+	u64 core_caps, mcg_cap;
+
+	if (!cpu_feature_enabled(X86_FEATURE_MCA))
+		return -ENODEV;
+	rdmsrq(MSR_IA32_MCG_CAP, mcg_cap);
+	if (!(mcg_cap & MCG_TES_P))
+		return -ENODEV;
+
+	if (!cpu_feature_enabled(X86_FEATURE_CORE_CAPABILITIES))
+		return -ENODEV;
+	rdmsrq(MSR_IA32_CORE_CAPS, core_caps);
+	if (!(core_caps & MSR_IA32_CORE_CAPS_BFF_RESET))
+		return -ENODEV;
+
+	return 0;
+}
+
+module_init(bff_init);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Tony Luck");
+MODULE_DESCRIPTION("Intel bitfix filter reset driver");
diff --git a/MAINTAINERS b/MAINTAINERS
index 8014b9f8253e..edc50f7cb025 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9405,6 +9405,12 @@ L:	linux-edac@xxxxxxxxxxxxxxx
 S:	Maintained
 F:	drivers/edac/igen6_edac.c
 
+EDAC-INTEL-BFF-RESET
+M:	Tony Luck <tony.luck@xxxxxxxxx>
+L:	linux-edac@xxxxxxxxxxxxxxx
+S:	Maintained
+F:	drivers/edac/intel-bff.c
+
 EDAC-MPC85XX
 M:	Johannes Thumshirn <morbidrsa@xxxxxxxxx>
 L:	linux-edac@xxxxxxxxxxxxxxx
diff --git a/drivers/edac/Kconfig b/drivers/edac/Kconfig
index a44b85c440ca..f7964cd9545e 100644
--- a/drivers/edac/Kconfig
+++ b/drivers/edac/Kconfig
@@ -280,6 +280,19 @@ config EDAC_IMH
 	  first used on the Diamond Rapids servers but may appear on
 	  others in the future.
 
+config EDAC_INTEL_BFF_RESET
+	tristate "Intel bitfix filter reset driver"
+	depends on X86_64 && X86_MCE_INTEL
+	help
+	  Support for Intel systems that implement bitfix filters to
+	  suppress repeated logging and signaling of the same corrected
+	  error. Those filters can become clogged with transient errors
+	  over time. Clearing the filter may make space for additional
+	  hard errors.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called intel_bff.
+
 config EDAC_PND2
 	tristate "Intel Pondicherry2"
 	depends on PCI && X86_64 && X86_MCE_INTEL
diff --git a/drivers/edac/Makefile b/drivers/edac/Makefile
index a37534300ab9..c2bae03f247b 100644
--- a/drivers/edac/Makefile
+++ b/drivers/edac/Makefile
@@ -66,6 +66,8 @@ obj-$(CONFIG_EDAC_I10NM)		+= i10nm_edac.o skx_edac_common.o
 imh_edac-y				:= imh_base.o
 obj-$(CONFIG_EDAC_IMH)			+= imh_edac.o skx_edac_common.o
 
+obj-$(CONFIG_EDAC_INTEL_BFF_RESET)	+= intel-bff.o
+
 obj-$(CONFIG_EDAC_HIGHBANK_MC)		+= highbank_mc_edac.o
 obj-$(CONFIG_EDAC_HIGHBANK_L2)		+= highbank_l2_edac.o
 
-- 
2.55.0