Hi Seb,

Thanks for the respin.

On Tue, Aug 27, 2024 at 08:45:47AM +0000, Sebastian Ene wrote:

While arch/*/mem/ptdump handles the kernel pagetable dumping code,
introduce KVM/ptdump to show the guest stage-2 pagetables. The
separation is necessary because most of the definitions from the
stage-2 pagetable reside in the KVM path and we will be invoking
functionality specific to KVM.

When a guest is created, register a new file entry under the guest
debugfs dir which allows userspace to show the contents of the guest
stage-2 pagetables when accessed.

Signed-off-by: Sebastian Ene <redacted>

I only have some nits, otherwise:

Reviewed-by: Vincent Donnefort <redacted>

nit: I believe you wanted to follow the alphabetical order, if that is the case,
kvm_host.h then kvm_pgtable.h

+#include <asm/ptdump.h>
+
+

nit: don't think double empty are a rule, I would remove it.

+#define MARKERS_LEN		(2)

nit: The brackets are not necessary for MARKERS_LEN.

+#define KVM_PGTABLE_MAX_LEVELS	(KVM_PGTABLE_LAST_LEVEL + 1)
+
+struct kvm_ptdump_guest_state {
+	struct kvm		*kvm;
+	struct ptdump_pg_state	parser_state;
+	struct addr_marker	ipa_marker[MARKERS_LEN];
+	struct ptdump_pg_level	level[KVM_PGTABLE_MAX_LEVELS];
+	struct ptdump_range	range[MARKERS_LEN];
+};
+
+static const struct ptdump_prot_bits stage2_pte_bits[] = {
+	{
+		.mask	= PTE_VALID,
+		.val	= PTE_VALID,
+		.set	= " ",
+		.clear	= "F",

This is effectively never used because an invalid PTE is 0 and note_page() won't
print it. This probably can be removed?

+	}, {
+		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | PTE_VALID,
+		.val	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | PTE_VALID,
+		.set	= "R",
+		.clear	= " ",
+	}, {
+		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | PTE_VALID,
+		.val	= KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | PTE_VALID,
+		.set	= "W",
+		.clear	= " ",
+	}, {
+		.mask	= KVM_PTE_LEAF_ATTR_HI_S2_XN | PTE_VALID,
+		.val	= PTE_VALID,
+		.set	= " ",
+		.clear	= "X",
+	}, {
+		.mask	= KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID,
+		.val	= KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID,
+		.set	= "AF",
+		.clear	= "  ",
+	}, {
+		.mask	= PTE_TABLE_BIT | PTE_VALID,
+		.val	= PTE_VALID,
+		.set	= "BLK",
+		.clear	= "   ",
+	},
+};
+
+static int kvm_ptdump_visitor(const struct kvm_pgtable_visit_ctx *ctx,
+			      enum kvm_pgtable_walk_flags visit)
+{
+	struct ptdump_pg_state *st = ctx->arg;
+	struct ptdump_state *pt_st = &st->ptdump;
+
+	note_page(pt_st, ctx->addr, ctx->level, ctx->old);
+
+	return 0;
+}
+
+static int kvm_ptdump_build_levels(struct ptdump_pg_level *level, u32 start_lvl)
+{
+	u32 i;
+	u64 mask;
+
+	if (WARN_ON_ONCE(start_lvl >= KVM_PGTABLE_LAST_LEVEL))
+		return -EINVAL;
+
+	mask = 0;
+	for (i = 0; i < ARRAY_SIZE(stage2_pte_bits); i++)
+		mask |= stage2_pte_bits[i].mask;
+
+	for (i = start_lvl; i < KVM_PGTABLE_MAX_LEVELS; i++) {
+		snprintf(level[i].name, sizeof(level[i].name), "%d", i);

%u, i being unsigned.

+
+		level[i].num	= ARRAY_SIZE(stage2_pte_bits);
+		level[i].bits	= stage2_pte_bits;
+		level[i].mask	= mask;
+	}
+
+	return 0;
+}
+
+static struct kvm_ptdump_guest_state *kvm_ptdump_parser_create(struct kvm *kvm)
+{
+	struct kvm_ptdump_guest_state *st;
+	struct kvm_s2_mmu *mmu = &kvm->arch.mmu;
+	struct kvm_pgtable *pgtable = mmu->pgt;
+	int ret;
+
+	st = kzalloc(sizeof(struct kvm_ptdump_guest_state), GFP_KERNEL_ACCOUNT);
+	if (!st)
+		return ERR_PTR(-ENOMEM);
+
+	ret = kvm_ptdump_build_levels(&st->level[0], pgtable->start_level);
+	if (ret) {
+		kfree(st);
+		return ERR_PTR(ret);
+	}
+
+	st->ipa_marker[0].name		= "Guest IPA";
+	st->ipa_marker[1].start_address = BIT(pgtable->ia_bits);
+	st->range[0].end		= BIT(pgtable->ia_bits);
+
+	st->kvm				= kvm;
+	st->parser_state = (struct ptdump_pg_state) {
+		.marker		= &st->ipa_marker[0],
+		.level		= -1,
+		.pg_level	= &st->level[0],
+		.ptdump.range	= &st->range[0],
+		.start_address	= 0,
+	};
+
+	return st;
+}
+
+static int kvm_ptdump_guest_show(struct seq_file *m, void *unused)
+{
+	int ret;
+	struct kvm_ptdump_guest_state *st = m->private;
+	struct kvm *kvm = st->kvm;
+	struct kvm_s2_mmu *mmu = &kvm->arch.mmu;
+	struct ptdump_pg_state *parser_state = &st->parser_state;
+	struct kvm_pgtable_walker walker = (struct kvm_pgtable_walker) {
+		.cb	= kvm_ptdump_visitor,
+		.arg	= parser_state,
+		.flags	= KVM_PGTABLE_WALK_LEAF,
+	};
+
+	parser_state->seq = m;
+
+	write_lock(&kvm->mmu_lock);
+	ret = kvm_pgtable_walk(mmu->pgt, 0, BIT(mmu->pgt->ia_bits), &walker);
+	write_unlock(&kvm->mmu_lock);
+
+	return ret;
+}
+
+static int kvm_ptdump_guest_open(struct inode *m, struct file *file)
+{
+	struct kvm *kvm = m->i_private;
+	struct kvm_ptdump_guest_state *st;
+	int ret;
+
+	if (!kvm_get_kvm_safe(kvm))
+		return -ENOENT;
+
+	st = kvm_ptdump_parser_create(kvm);
+	if (IS_ERR(st)) {
+		ret = PTR_ERR(st);
+		goto free_with_kvm_ref;
+	}
+
+	ret = single_open(file, kvm_ptdump_guest_show, st);
+	if (!ret)
+		return 0;
+
+	kfree(st);
+free_with_kvm_ref:

nit: I believe kfree understands IS_ERR() so you could have a simple "err:"
label covering all the error path.

+	kvm_put_kvm(kvm);
+	return ret;
+}
+
+static int kvm_ptdump_guest_close(struct inode *m, struct file *file)
+{
+	struct kvm *kvm = m->i_private;
+	void *st = ((struct seq_file *)file->private_data)->private;
+
+	kfree(st);
+	kvm_put_kvm(kvm);
+
+	return single_release(m, file);
+}
+
+static const struct file_operations kvm_ptdump_guest_fops = {
+	.open		= kvm_ptdump_guest_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.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);

nit: KVM_PGTABLE_MAX_LEVELS - pgtable->start_level ?

+	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_s2_ptdump_create_debugfs(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);
+}
-- 
2.46.0.295.g3b9ea8a38a-goog