KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 224 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-efi.c b/drivers/rtc/rtc-efi.c
new file mode 100644
index 000000000..b4f44999e
--- /dev/null
+++ b/drivers/rtc/rtc-efi.c
@@ -0,0 +1,224 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * rtc-efi: RTC Class Driver for EFI-based systems
+ *
+ * Copyright (C) 2009 Hewlett-Packard Development Company, L.P.
+ *
+ * Author: dann frazier <dannf@dannf.org>
+ * Based on efirtc.c by Stephane Eranian
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/stringify.h>
+#include <linux/time.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/efi.h>
+
+#define EFI_ISDST (EFI_TIME_ADJUST_DAYLIGHT|EFI_TIME_IN_DAYLIGHT)
+
+/*
+ * returns day of the year [0-365]
+ */
+static inline int
+compute_yday(efi_time_t *eft)
+{
+	/* efi_time_t.month is in the [1-12] so, we need -1 */
+	return rtc_year_days(eft->day, eft->month - 1, eft->year);
+}
+
+/*
+ * returns day of the week [0-6] 0=Sunday
+ */
+static int
+compute_wday(efi_time_t *eft, int yday)
+{
+	int ndays = eft->year * (365 % 7)
+		    + (eft->year - 1) / 4
+		    - (eft->year - 1) / 100
+		    + (eft->year - 1) / 400
+		    + yday;
+
+	/*
+	 * 1/1/0000 may or may not have been a Sunday (if it ever existed at
+	 * all) but assuming it was makes this calculation work correctly.
+	 */
+	return ndays % 7;
+}
+
+static void
+convert_to_efi_time(struct rtc_time *wtime, efi_time_t *eft)
+{
+	eft->year	= wtime->tm_year + 1900;
+	eft->month	= wtime->tm_mon + 1;
+	eft->day	= wtime->tm_mday;
+	eft->hour	= wtime->tm_hour;
+	eft->minute	= wtime->tm_min;
+	eft->second	= wtime->tm_sec;
+	eft->nanosecond = 0;
+	eft->daylight	= wtime->tm_isdst ? EFI_ISDST : 0;
+	eft->timezone	= EFI_UNSPECIFIED_TIMEZONE;
+}
+
+static bool
+convert_from_efi_time(efi_time_t *eft, struct rtc_time *wtime)
+{
+	memset(wtime, 0, sizeof(*wtime));
+
+	if (eft->second >= 60)
+		return false;
+	wtime->tm_sec  = eft->second;
+
+	if (eft->minute >= 60)
+		return false;
+	wtime->tm_min  = eft->minute;
+
+	if (eft->hour >= 24)
+		return false;
+	wtime->tm_hour = eft->hour;
+
+	if (!eft->day || eft->day > 31)
+		return false;
+	wtime->tm_mday = eft->day;
+
+	if (!eft->month || eft->month > 12)
+		return false;
+	wtime->tm_mon  = eft->month - 1;
+
+	if (eft->year < 1900 || eft->year > 9999)
+		return false;
+	wtime->tm_year = eft->year - 1900;
+
+	/* day in the year [1-365]*/
+	wtime->tm_yday = compute_yday(eft);
+
+	/* day of the week [0-6], Sunday=0 */
+	wtime->tm_wday = compute_wday(eft, wtime->tm_yday);
+
+	switch (eft->daylight & EFI_ISDST) {
+	case EFI_ISDST:
+		wtime->tm_isdst = 1;
+		break;
+	case EFI_TIME_ADJUST_DAYLIGHT:
+		wtime->tm_isdst = 0;
+		break;
+	default:
+		wtime->tm_isdst = -1;
+	}
+
+	return true;
+}
+
+static int efi_read_time(struct device *dev, struct rtc_time *tm)
+{
+	efi_status_t status;
+	efi_time_t eft;
+	efi_time_cap_t cap;
+
+	status = efi.get_time(&eft, &cap);
+
+	if (status != EFI_SUCCESS) {
+		/* should never happen */
+		dev_err_once(dev, "can't read time\n");
+		return -EINVAL;
+	}
+
+	if (!convert_from_efi_time(&eft, tm))
+		return -EIO;
+
+	return 0;
+}
+
+static int efi_set_time(struct device *dev, struct rtc_time *tm)
+{
+	efi_status_t status;
+	efi_time_t eft;
+
+	convert_to_efi_time(tm, &eft);
+
+	status = efi.set_time(&eft);
+
+	return status == EFI_SUCCESS ? 0 : -EINVAL;
+}
+
+static int efi_procfs(struct device *dev, struct seq_file *seq)
+{
+	efi_time_t        eft;
+	efi_time_cap_t    cap;
+
+	memset(&eft, 0, sizeof(eft));
+	memset(&cap, 0, sizeof(cap));
+
+	efi.get_time(&eft, &cap);
+
+	seq_printf(seq,
+		   "Time\t\t: %u:%u:%u.%09u\n"
+		   "Date\t\t: %u-%u-%u\n"
+		   "Daylight\t: %u\n",
+		   eft.hour, eft.minute, eft.second, eft.nanosecond,
+		   eft.year, eft.month, eft.day,
+		   eft.daylight);
+
+	if (eft.timezone == EFI_UNSPECIFIED_TIMEZONE)
+		seq_puts(seq, "Timezone\t: unspecified\n");
+	else
+		/* XXX fixme: convert to string? */
+		seq_printf(seq, "Timezone\t: %u\n", eft.timezone);
+
+	/*
+	 * now prints the capabilities
+	 */
+	seq_printf(seq,
+		   "Resolution\t: %u\n"
+		   "Accuracy\t: %u\n"
+		   "SetstoZero\t: %u\n",
+		   cap.resolution, cap.accuracy, cap.sets_to_zero);
+
+	return 0;
+}
+
+static const struct rtc_class_ops efi_rtc_ops = {
+	.read_time	= efi_read_time,
+	.set_time	= efi_set_time,
+	.proc		= efi_procfs,
+};
+
+static int __init efi_rtc_probe(struct platform_device *dev)
+{
+	struct rtc_device *rtc;
+	efi_time_t eft;
+	efi_time_cap_t cap;
+
+	/* First check if the RTC is usable */
+	if (efi.get_time(&eft, &cap) != EFI_SUCCESS)
+		return -ENODEV;
+
+	rtc = devm_rtc_allocate_device(&dev->dev);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	platform_set_drvdata(dev, rtc);
+
+	rtc->ops = &efi_rtc_ops;
+	clear_bit(RTC_FEATURE_ALARM, rtc->features);
+
+	device_init_wakeup(&dev->dev, true);
+
+	return devm_rtc_register_device(rtc);
+}
+
+static struct platform_driver efi_rtc_driver = {
+	.driver = {
+		.name = "rtc-efi",
+	},
+};
+
+module_platform_driver_probe(efi_rtc_driver, efi_rtc_probe);
+
+MODULE_AUTHOR("dann frazier <dannf@dannf.org>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("EFI RTC driver");
+MODULE_ALIAS("platform:rtc-efi");