[PATCH 3/7] platform/x86/intel/bff: Add stub Intel bitfix filter driver

[Tony Luck]

Check if platform supports enhanced 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/platform/x86/intel/bff.c    | 59 +++++++++++++++++++++++++++++
 drivers/platform/x86/intel/Kconfig  | 13 +++++++
 drivers/platform/x86/intel/Makefile |  1 +
 3 files changed, 73 insertions(+)
 create mode 100644 drivers/platform/x86/intel/bff.c

diff --git a/drivers/platform/x86/intel/bff.c b/drivers/platform/x86/intel/bff.c
new file mode 100644
index 000000000000..9522bdb1401d
--- /dev/null
+++ b/drivers/platform/x86/intel/bff.c
@@ -0,0 +1,59 @@
+// 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) "bff: " 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_DETECT))
+		return -ENODEV;
+
+	return 0;
+}
+
+static void __exit bff_exit(void)
+{
+}
+
+module_init(bff_init);
+module_exit(bff_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Intel bitfix filter reset driver");
diff --git a/drivers/platform/x86/intel/Kconfig b/drivers/platform/x86/intel/Kconfig
index 2900407d6095..f4e9af0116ee 100644
--- a/drivers/platform/x86/intel/Kconfig
+++ b/drivers/platform/x86/intel/Kconfig
@@ -251,3 +251,16 @@ config INTEL_VSEC
 
 	  To compile this driver as a module, choose M here: the module will
 	  be called intel_vsec.
+
+config INTEL_BFF_RESET
+	tristate "Intel bitfix filter reset driver"
+	depends on CPU_SUP_INTEL && X86_MCE
+	help
+	  Adds 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.
diff --git a/drivers/platform/x86/intel/Makefile b/drivers/platform/x86/intel/Makefile
index 138b13756158..dc4e374758d5 100644
--- a/drivers/platform/x86/intel/Makefile
+++ b/drivers/platform/x86/intel/Makefile
@@ -27,6 +27,7 @@ intel-target-$(CONFIG_INTEL_ISHTP_ECLITE)	+= ishtp_eclite.o
 intel-target-$(CONFIG_INTEL_OAKTRAIL)		+= oaktrail.o
 intel-target-$(CONFIG_INTEL_SDSI)		+= sdsi.o
 intel-target-$(CONFIG_INTEL_VSEC)		+= vsec.o
+intel-target-$(CONFIG_INTEL_BFF_RESET)		+= bff.o
 
 # Intel PMIC / PMC / P-Unit drivers
 intel-target-$(CONFIG_INTEL_BYTCRC_PWRSRC)	+= bytcrc_pwrsrc.o
-- 
2.55.0