linux-kernel - [PATCH v8 6/6] KVM: arm64: Expose guest stage-2 pagetable config to debugfs

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Message-ID: <20240816123906.3683425-7-sebastianene@google.com>
Date: Fri, 16 Aug 2024 12:39:06 +0000
From: Sebastian Ene <sebastianene@...gle.com>
To: akpm@...ux-foundation.org, alexghiti@...osinc.com, ankita@...dia.com, 
	ardb@...nel.org, catalin.marinas@....com, christophe.leroy@...roup.eu, 
	james.morse@....com, vdonnefort@...gle.com, mark.rutland@....com, 
	maz@...nel.org, oliver.upton@...ux.dev, rananta@...gle.com, 
	ryan.roberts@....com, sebastianene@...gle.com, shahuang@...hat.com, 
	suzuki.poulose@....com, will@...nel.org, yuzenghui@...wei.com
Cc: kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, kernel-team@...roid.com
Subject: [PATCH v8 6/6] KVM: arm64: Expose guest stage-2 pagetable config to debugfs

Make the start level and the IPA bits properties available in the
virtual machine debugfs directory. Make sure that the KVM structure
doesn't disappear behind our back and keep a reference to the KVM struct
while these files are opened.

Signed-off-by: Sebastian Ene <sebastianene@...gle.com>
---
 arch/arm64/kvm/ptdump.c | 48 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
index 79be07ec3c3c..b0d55ea3fb2a 100644
--- a/arch/arm64/kvm/ptdump.c
+++ b/arch/arm64/kvm/ptdump.c
@@ -207,8 +207,56 @@ static const struct file_operations kvm_ptdump_guest_fops = {
 	.release	= kvm_ptdump_guest_close,
 };
 
+static int kvm_pgtable_debugfs_show(struct seq_file *m, void *unused)
+{
+	const struct file *file = m->file;
+	struct kvm_pgtable *pgtable = m->private;
+
+	if (!strcmp(file_dentry(file)->d_iname, "ipa_range"))
+		seq_printf(m, "%2u\n", pgtable->ia_bits);
+	else if (!strcmp(file_dentry(file)->d_iname, "stage2_levels"))
+		seq_printf(m, "%1d\n", KVM_PGTABLE_LAST_LEVEL - pgtable->start_level + 1);
+	return 0;
+}
+
+static int kvm_pgtable_debugfs_open(struct inode *m, struct file *file)
+{
+	struct kvm *kvm = m->i_private;
+	struct kvm_pgtable *pgtable;
+	int ret;
+
+	if (!kvm_get_kvm_safe(kvm))
+		return -ENOENT;
+
+	pgtable = kvm->arch.mmu.pgt;
+
+	ret = single_open(file, kvm_pgtable_debugfs_show, pgtable);
+	if (ret < 0)
+		kvm_put_kvm(kvm);
+	return ret;
+}
+
+static int kvm_pgtable_debugfs_close(struct inode *m, struct file *file)
+{
+	struct kvm *kvm = m->i_private;
+
+	kvm_put_kvm(kvm);
+	return single_release(m, file);
+}
+
+static const struct file_operations kvm_pgtable_debugfs_fops = {
+	.open		= kvm_pgtable_debugfs_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= kvm_pgtable_debugfs_close,
+};
+
 void kvm_ptdump_guest_register(struct kvm *kvm)
 {
 	debugfs_create_file("stage2_page_tables", 0400, kvm->debugfs_dentry,
 			    kvm, &kvm_ptdump_guest_fops);
+	debugfs_create_file("ipa_range", 0400, kvm->debugfs_dentry, kvm,
+			    &kvm_pgtable_debugfs_fops);
+	debugfs_create_file("stage2_levels", 0400, kvm->debugfs_dentry,
+			    kvm, &kvm_pgtable_debugfs_fops);
 }
-- 
2.46.0.184.g6999bdac58-goog