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, 196 insertions, 0 deletions

diff --git a/arch/x86/kvm/debugfs.c b/arch/x86/kvm/debugfs.c
new file mode 100644
index 000000000..0074a56e4
--- /dev/null
+++ b/arch/x86/kvm/debugfs.c
@@ -0,0 +1,196 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Kernel-based Virtual Machine driver for Linux
+ *
+ * Copyright 2016 Red Hat, Inc. and/or its affiliates.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kvm_host.h>
+#include <linux/debugfs.h>
+#include "lapic.h"
+#include "mmu.h"
+#include "mmu/mmu_internal.h"
+
+static int vcpu_get_timer_advance_ns(void *data, u64 *val)
+{
+	struct kvm_vcpu *vcpu = (struct kvm_vcpu *) data;
+	*val = vcpu->arch.apic->lapic_timer.timer_advance_ns;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(vcpu_timer_advance_ns_fops, vcpu_get_timer_advance_ns, NULL, "%llu\n");
+
+static int vcpu_get_guest_mode(void *data, u64 *val)
+{
+	struct kvm_vcpu *vcpu = (struct kvm_vcpu *) data;
+	*val = vcpu->stat.guest_mode;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(vcpu_guest_mode_fops, vcpu_get_guest_mode, NULL, "%lld\n");
+
+static int vcpu_get_tsc_offset(void *data, u64 *val)
+{
+	struct kvm_vcpu *vcpu = (struct kvm_vcpu *) data;
+	*val = vcpu->arch.tsc_offset;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(vcpu_tsc_offset_fops, vcpu_get_tsc_offset, NULL, "%lld\n");
+
+static int vcpu_get_tsc_scaling_ratio(void *data, u64 *val)
+{
+	struct kvm_vcpu *vcpu = (struct kvm_vcpu *) data;
+	*val = vcpu->arch.tsc_scaling_ratio;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(vcpu_tsc_scaling_fops, vcpu_get_tsc_scaling_ratio, NULL, "%llu\n");
+
+static int vcpu_get_tsc_scaling_frac_bits(void *data, u64 *val)
+{
+	*val = kvm_caps.tsc_scaling_ratio_frac_bits;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(vcpu_tsc_scaling_frac_fops, vcpu_get_tsc_scaling_frac_bits, NULL, "%llu\n");
+
+void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu, struct dentry *debugfs_dentry)
+{
+	debugfs_create_file("guest_mode", 0444, debugfs_dentry, vcpu,
+			    &vcpu_guest_mode_fops);
+	debugfs_create_file("tsc-offset", 0444, debugfs_dentry, vcpu,
+			    &vcpu_tsc_offset_fops);
+
+	if (lapic_in_kernel(vcpu))
+		debugfs_create_file("lapic_timer_advance_ns", 0444,
+				    debugfs_dentry, vcpu,
+				    &vcpu_timer_advance_ns_fops);
+
+	if (kvm_caps.has_tsc_control) {
+		debugfs_create_file("tsc-scaling-ratio", 0444,
+				    debugfs_dentry, vcpu,
+				    &vcpu_tsc_scaling_fops);
+		debugfs_create_file("tsc-scaling-ratio-frac-bits", 0444,
+				    debugfs_dentry, vcpu,
+				    &vcpu_tsc_scaling_frac_fops);
+	}
+}
+
+/*
+ * This covers statistics <1024 (11=log(1024)+1), which should be enough to
+ * cover RMAP_RECYCLE_THRESHOLD.
+ */
+#define  RMAP_LOG_SIZE  11
+
+static const char *kvm_lpage_str[KVM_NR_PAGE_SIZES] = { "4K", "2M", "1G" };
+
+static int kvm_mmu_rmaps_stat_show(struct seq_file *m, void *v)
+{
+	struct kvm_rmap_head *rmap;
+	struct kvm *kvm = m->private;
+	struct kvm_memory_slot *slot;
+	struct kvm_memslots *slots;
+	unsigned int lpage_size, index;
+	/* Still small enough to be on the stack */
+	unsigned int *log[KVM_NR_PAGE_SIZES], *cur;
+	int i, j, k, l, ret;
+
+	if (!kvm_memslots_have_rmaps(kvm))
+		return 0;
+
+	ret = -ENOMEM;
+	memset(log, 0, sizeof(log));
+	for (i = 0; i < KVM_NR_PAGE_SIZES; i++) {
+		log[i] = kcalloc(RMAP_LOG_SIZE, sizeof(unsigned int), GFP_KERNEL);
+		if (!log[i])
+			goto out;
+	}
+
+	mutex_lock(&kvm->slots_lock);
+	write_lock(&kvm->mmu_lock);
+
+	for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) {
+		int bkt;
+
+		slots = __kvm_memslots(kvm, i);
+		kvm_for_each_memslot(slot, bkt, slots)
+			for (k = 0; k < KVM_NR_PAGE_SIZES; k++) {
+				rmap = slot->arch.rmap[k];
+				lpage_size = kvm_mmu_slot_lpages(slot, k + 1);
+				cur = log[k];
+				for (l = 0; l < lpage_size; l++) {
+					index = fls(pte_list_count(&rmap[l]));
+					if (WARN_ON_ONCE(index >= RMAP_LOG_SIZE))
+						index = RMAP_LOG_SIZE - 1;
+					cur[index]++;
+				}
+			}
+	}
+
+	write_unlock(&kvm->mmu_lock);
+	mutex_unlock(&kvm->slots_lock);
+
+	/* index=0 counts no rmap; index=1 counts 1 rmap */
+	seq_printf(m, "Rmap_Count:\t0\t1\t");
+	for (i = 2; i < RMAP_LOG_SIZE; i++) {
+		j = 1 << (i - 1);
+		k = (1 << i) - 1;
+		seq_printf(m, "%d-%d\t", j, k);
+	}
+	seq_printf(m, "\n");
+
+	for (i = 0; i < KVM_NR_PAGE_SIZES; i++) {
+		seq_printf(m, "Level=%s:\t", kvm_lpage_str[i]);
+		cur = log[i];
+		for (j = 0; j < RMAP_LOG_SIZE; j++)
+			seq_printf(m, "%d\t", cur[j]);
+		seq_printf(m, "\n");
+	}
+
+	ret = 0;
+out:
+	for (i = 0; i < KVM_NR_PAGE_SIZES; i++)
+		kfree(log[i]);
+
+	return ret;
+}
+
+static int kvm_mmu_rmaps_stat_open(struct inode *inode, struct file *file)
+{
+	struct kvm *kvm = inode->i_private;
+	int r;
+
+	if (!kvm_get_kvm_safe(kvm))
+		return -ENOENT;
+
+	r = single_open(file, kvm_mmu_rmaps_stat_show, kvm);
+	if (r < 0)
+		kvm_put_kvm(kvm);
+
+	return r;
+}
+
+static int kvm_mmu_rmaps_stat_release(struct inode *inode, struct file *file)
+{
+	struct kvm *kvm = inode->i_private;
+
+	kvm_put_kvm(kvm);
+
+	return single_release(inode, file);
+}
+
+static const struct file_operations mmu_rmaps_stat_fops = {
+	.owner		= THIS_MODULE,
+	.open		= kvm_mmu_rmaps_stat_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= kvm_mmu_rmaps_stat_release,
+};
+
+void kvm_arch_create_vm_debugfs(struct kvm *kvm)
+{
+	debugfs_create_file("mmu_rmaps_stat", 0644, kvm->debugfs_dentry, kvm,
+			    &mmu_rmaps_stat_fops);
+}