1 files changed, 101 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/dawr.c b/arch/powerpc/kernel/dawr.c
new file mode 100644
index 000000000000..5f66b95b6858
--- /dev/null
+++ b/arch/powerpc/kernel/dawr.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * DAWR infrastructure
+ *
+ * Copyright 2019, Michael Neuling, IBM Corporation.
+ */
+
+#include <linux/types.h>
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <asm/debugfs.h>
+#include <asm/machdep.h>
+#include <asm/hvcall.h>
+
+bool dawr_force_enable;
+EXPORT_SYMBOL_GPL(dawr_force_enable);
+
+int set_dawr(struct arch_hw_breakpoint *brk)
+{
+	unsigned long dawr, dawrx, mrd;
+
+	dawr = brk->address;
+
+	dawrx  = (brk->type & (HW_BRK_TYPE_READ | HW_BRK_TYPE_WRITE))
+		<< (63 - 58);
+	dawrx |= ((brk->type & (HW_BRK_TYPE_TRANSLATE)) >> 2) << (63 - 59);
+	dawrx |= (brk->type & (HW_BRK_TYPE_PRIV_ALL)) >> 3;
+	/*
+	 * DAWR length is stored in field MDR bits 48:53.  Matches range in
+	 * doublewords (64 bits) baised by -1 eg. 0b000000=1DW and
+	 * 0b111111=64DW.
+	 * brk->len is in bytes.
+	 * This aligns up to double word size, shifts and does the bias.
+	 */
+	mrd = ((brk->len + 7) >> 3) - 1;
+	dawrx |= (mrd & 0x3f) << (63 - 53);
+
+	if (ppc_md.set_dawr)
+		return ppc_md.set_dawr(dawr, dawrx);
+
+	mtspr(SPRN_DAWR, dawr);
+	mtspr(SPRN_DAWRX, dawrx);
+
+	return 0;
+}
+
+static void set_dawr_cb(void *info)
+{
+	set_dawr(info);
+}
+
+static ssize_t dawr_write_file_bool(struct file *file,
+				    const char __user *user_buf,
+				    size_t count, loff_t *ppos)
+{
+	struct arch_hw_breakpoint null_brk = {0, 0, 0};
+	size_t rc;
+
+	/* Send error to user if they hypervisor won't allow us to write DAWR */
+	if (!dawr_force_enable &&
+	    firmware_has_feature(FW_FEATURE_LPAR) &&
+	    set_dawr(&null_brk) != H_SUCCESS)
+		return -ENODEV;
+
+	rc = debugfs_write_file_bool(file, user_buf, count, ppos);
+	if (rc)
+		return rc;
+
+	/* If we are clearing, make sure all CPUs have the DAWR cleared */
+	if (!dawr_force_enable)
+		smp_call_function(set_dawr_cb, &null_brk, 0);
+
+	return rc;
+}
+
+static const struct file_operations dawr_enable_fops = {
+	.read =		debugfs_read_file_bool,
+	.write =	dawr_write_file_bool,
+	.open =		simple_open,
+	.llseek =	default_llseek,
+};
+
+static int __init dawr_force_setup(void)
+{
+	if (cpu_has_feature(CPU_FTR_DAWR)) {
+		/* Don't setup sysfs file for user control on P8 */
+		dawr_force_enable = true;
+		return 0;
+	}
+
+	if (PVR_VER(mfspr(SPRN_PVR)) == PVR_POWER9) {
+		/* Turn DAWR off by default, but allow admin to turn it on */
+		debugfs_create_file_unsafe("dawr_enable_dangerous", 0600,
+					   powerpc_debugfs_root,
+					   &dawr_force_enable,
+					   &dawr_enable_fops);
+	}
+	return 0;
+}
+arch_initcall(dawr_force_setup);