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, 154 insertions, 0 deletions

diff --git a/arch/mips/sgi-ip27/ip27-timer.c b/arch/mips/sgi-ip27/ip27-timer.c
new file mode 100644
index 000000000..5f4da05cb
--- /dev/null
+++ b/arch/mips/sgi-ip27/ip27-timer.c
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 1999, 2000, 05, 06 Ralf Baechle (ralf@linux-mips.org)
+ * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
+ */
+#include <linux/bcd.h>
+#include <linux/clockchips.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/sched_clock.h>
+#include <linux/interrupt.h>
+#include <linux/kernel_stat.h>
+#include <linux/param.h>
+#include <linux/smp.h>
+#include <linux/time.h>
+#include <linux/timex.h>
+#include <linux/mm.h>
+#include <linux/platform_device.h>
+
+#include <asm/time.h>
+#include <asm/sgialib.h>
+#include <asm/sn/klconfig.h>
+#include <asm/sn/arch.h>
+#include <asm/sn/addrs.h>
+#include <asm/sn/agent.h>
+
+#include "ip27-common.h"
+
+static int rt_next_event(unsigned long delta, struct clock_event_device *evt)
+{
+	unsigned int cpu = smp_processor_id();
+	int slice = cputoslice(cpu);
+	unsigned long cnt;
+
+	cnt = LOCAL_HUB_L(PI_RT_COUNT);
+	cnt += delta;
+	LOCAL_HUB_S(PI_RT_COMPARE_A + PI_COUNT_OFFSET * slice, cnt);
+
+	return LOCAL_HUB_L(PI_RT_COUNT) >= cnt ? -ETIME : 0;
+}
+
+static DEFINE_PER_CPU(struct clock_event_device, hub_rt_clockevent);
+static DEFINE_PER_CPU(char [11], hub_rt_name);
+
+static irqreturn_t hub_rt_counter_handler(int irq, void *dev_id)
+{
+	unsigned int cpu = smp_processor_id();
+	struct clock_event_device *cd = &per_cpu(hub_rt_clockevent, cpu);
+	int slice = cputoslice(cpu);
+
+	/*
+	 * Ack
+	 */
+	LOCAL_HUB_S(PI_RT_PEND_A + PI_COUNT_OFFSET * slice, 0);
+	cd->event_handler(cd);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * This is a hack; we really need to figure these values out dynamically
+ *
+ * Since 800 ns works very well with various HUB frequencies, such as
+ * 360, 380, 390 and 400 MHZ, we use 800 ns rtc cycle time.
+ *
+ * Ralf: which clock rate is used to feed the counter?
+ */
+#define NSEC_PER_CYCLE		800
+#define CYCLES_PER_SEC		(NSEC_PER_SEC / NSEC_PER_CYCLE)
+
+void hub_rt_clock_event_init(void)
+{
+	unsigned int cpu = smp_processor_id();
+	struct clock_event_device *cd = &per_cpu(hub_rt_clockevent, cpu);
+	unsigned char *name = per_cpu(hub_rt_name, cpu);
+
+	sprintf(name, "hub-rt %d", cpu);
+	cd->name		= name;
+	cd->features		= CLOCK_EVT_FEAT_ONESHOT;
+	clockevent_set_clock(cd, CYCLES_PER_SEC);
+	cd->max_delta_ns	= clockevent_delta2ns(0xfffffffffffff, cd);
+	cd->max_delta_ticks	= 0xfffffffffffff;
+	cd->min_delta_ns	= clockevent_delta2ns(0x300, cd);
+	cd->min_delta_ticks	= 0x300;
+	cd->rating		= 200;
+	cd->irq			= IP27_RT_TIMER_IRQ;
+	cd->cpumask		= cpumask_of(cpu);
+	cd->set_next_event	= rt_next_event;
+	clockevents_register_device(cd);
+
+	enable_percpu_irq(IP27_RT_TIMER_IRQ, IRQ_TYPE_NONE);
+}
+
+static void __init hub_rt_clock_event_global_init(void)
+{
+	irq_set_handler(IP27_RT_TIMER_IRQ, handle_percpu_devid_irq);
+	irq_set_percpu_devid(IP27_RT_TIMER_IRQ);
+	WARN_ON(request_percpu_irq(IP27_RT_TIMER_IRQ, hub_rt_counter_handler,
+				   "hub-rt", &hub_rt_clockevent));
+}
+
+static u64 hub_rt_read(struct clocksource *cs)
+{
+	return REMOTE_HUB_L(cputonasid(0), PI_RT_COUNT);
+}
+
+struct clocksource hub_rt_clocksource = {
+	.name	= "HUB-RT",
+	.rating = 200,
+	.read	= hub_rt_read,
+	.mask	= CLOCKSOURCE_MASK(52),
+	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static u64 notrace hub_rt_read_sched_clock(void)
+{
+	return REMOTE_HUB_L(cputonasid(0), PI_RT_COUNT);
+}
+
+static void __init hub_rt_clocksource_init(void)
+{
+	struct clocksource *cs = &hub_rt_clocksource;
+
+	clocksource_register_hz(cs, CYCLES_PER_SEC);
+
+	sched_clock_register(hub_rt_read_sched_clock, 52, CYCLES_PER_SEC);
+}
+
+void __init plat_time_init(void)
+{
+	hub_rt_clocksource_init();
+	hub_rt_clock_event_global_init();
+	hub_rt_clock_event_init();
+}
+
+void hub_rtc_init(nasid_t nasid)
+{
+
+	/*
+	 * We only need to initialize the current node.
+	 * If this is not the current node then it is a cpuless
+	 * node and timeouts will not happen there.
+	 */
+	if (get_nasid() == nasid) {
+		LOCAL_HUB_S(PI_RT_EN_A, 1);
+		LOCAL_HUB_S(PI_RT_EN_B, 1);
+		LOCAL_HUB_S(PI_PROF_EN_A, 0);
+		LOCAL_HUB_S(PI_PROF_EN_B, 0);
+		LOCAL_HUB_S(PI_RT_COUNT, 0);
+		LOCAL_HUB_S(PI_RT_PEND_A, 0);
+		LOCAL_HUB_S(PI_RT_PEND_B, 0);
+	}
+}