arm64/boot: Disable trapping of PMZR_EL0 writes to EL2grafted

__init_el2_fgt2() writes one mask to both HDFGRTR2_EL2 and HDFGWTR2_EL2.
PMZR_EL0 is write-only, so its trap bit, nPMZR_EL0, exists only in
HDFGWTR2_EL2 and is therefore never set: a PMZR_EL0 write from the host
traps to EL2, where the nVHE hypervisor has no handler and BUG()s. The
kernel never writes PMZR_EL0, but kernel.perf_user_access=1 has the PMU
driver set PMUSERENR_EL0.UEN for a task with a user-read event, so a
write from EL0 reaches the trap and takes the host down without a panic
message.

Accumulate the HDFGWTR2_EL2 bits separately, as __init_el2_fgt() already
does for HDFGWTR_EL2, and set nPMZR_EL0 with the other FEAT_PMUv3p9
bits.

Fixes: 858c7bfcb35e1 ("arm64/boot: Enable EL2 requirements for FEAT_PMUv3p9")
Cc: stable@vger.kernel.org
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Oliver Upton <oupton@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 60 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-starfire.c b/drivers/rtc/rtc-starfire.c
new file mode 100644
index 000000000..fbd1ed41c
--- /dev/null
+++ b/drivers/rtc/rtc-starfire.c
@@ -0,0 +1,60 @@
+/* rtc-starfire.c: Starfire platform RTC driver.
+ *
+ * Author: David S. Miller
+ * License: GPL
+ *
+ * Copyright (C) 2008 David S. Miller <davem@davemloft.net>
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/rtc.h>
+#include <linux/platform_device.h>
+
+#include <asm/oplib.h>
+
+static u32 starfire_get_time(void)
+{
+	static char obp_gettod[32];
+	static u32 unix_tod;
+
+	sprintf(obp_gettod, "h# %08x unix-gettod",
+		(unsigned int) (long) &unix_tod);
+	prom_feval(obp_gettod);
+
+	return unix_tod;
+}
+
+static int starfire_read_time(struct device *dev, struct rtc_time *tm)
+{
+	rtc_time64_to_tm(starfire_get_time(), tm);
+	return 0;
+}
+
+static const struct rtc_class_ops starfire_rtc_ops = {
+	.read_time	= starfire_read_time,
+};
+
+static int __init starfire_rtc_probe(struct platform_device *pdev)
+{
+	struct rtc_device *rtc;
+
+	rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	rtc->ops = &starfire_rtc_ops;
+	rtc->range_max = U32_MAX;
+
+	platform_set_drvdata(pdev, rtc);
+
+	return devm_rtc_register_device(rtc);
+}
+
+static struct platform_driver starfire_rtc_driver = {
+	.driver		= {
+		.name	= "rtc-starfire",
+	},
+};
+
+builtin_platform_driver_probe(starfire_rtc_driver, starfire_rtc_probe);