linux-kernel - [PATCH v4 10/10] arm64: ptdump: Add guest stage-2 pagetables dumping

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Message-ID: <20231218135859.2513568-12-sebastianene@google.com>
Date: Mon, 18 Dec 2023 13:59:00 +0000
From: Sebastian Ene <sebastianene@...gle.com>
To: will@...nel.org, Oliver Upton <oliver.upton@...ux.dev>, 
	James Morse <james.morse@....com>, Suzuki K Poulose <suzuki.poulose@....com>, 
	Zenghui Yu <yuzenghui@...wei.com>, catalin.marinas@....com, mark.rutland@....com, 
	akpm@...ux-foundation.org, maz@...nel.org
Cc: kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, kernel-team@...roid.com, vdonnefort@...gle.com, 
	qperret@...gle.com, smostafa@...gle.com, 
	Sebastian Ene <sebastianene@...gle.com>
Subject: [PATCH v4 10/10] arm64: ptdump: Add guest stage-2 pagetables dumping

Register a debugfs file on guest creation to be able to view their
second translation tables with ptdump. This assumes that the host is in
control of the guest stage-2 and has direct access to the pagetables.

Signed-off-by: Sebastian Ene <sebastianene@...gle.com>
---
 arch/arm64/kvm/debug.c      |  6 ++++++
 arch/arm64/kvm/kvm_ptdump.h |  3 +++
 arch/arm64/kvm/ptdump.c     | 35 ++++++++++++++++++++++++++++++++---
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index 8725291cb..7c4c2902d 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -13,6 +13,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_arm.h>
 #include <asm/kvm_emulate.h>
+#include <kvm_ptdump.h>
 
 #include "trace.h"
 
@@ -342,3 +343,8 @@ void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu)
 	vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_SPE);
 	vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_TRBE);
 }
+
+int kvm_arch_create_vm_debugfs(struct kvm *kvm)
+{
+	return kvm_ptdump_register_guest(kvm);
+}
diff --git a/arch/arm64/kvm/kvm_ptdump.h b/arch/arm64/kvm/kvm_ptdump.h
index 98b595ce8..5f5a455d0 100644
--- a/arch/arm64/kvm/kvm_ptdump.h
+++ b/arch/arm64/kvm/kvm_ptdump.h
@@ -6,13 +6,16 @@
 #ifndef __KVM_PTDUMP_H
 #define __KVM_PTDUMP_H
 
+#include <linux/kvm_host.h>
 #include <asm/ptdump.h>
 
 
 #ifdef CONFIG_PTDUMP_STAGE2_DEBUGFS
 void kvm_ptdump_register_host(void);
+int kvm_ptdump_register_guest(struct kvm *kvm);
 #else
 static inline void kvm_ptdump_register_host(void) { }
+static inline int kvm_ptdump_register_guest(struct kvm *kvm) { return -1; }
 #endif /* CONFIG_PTDUMP_STAGE2_DEBUGFS */
 
 #endif /* __KVM_PTDUMP_H */
diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
index 4296e739f..62a753d6b 100644
--- a/arch/arm64/kvm/ptdump.c
+++ b/arch/arm64/kvm/ptdump.c
@@ -181,6 +181,8 @@ static int kvm_ptdump_open(struct inode *inode, struct file *file)
 		info = reg->get_ptdump_info(reg);
 		if (!info)
 			return -ENOMEM;
+	} else {
+		info = inode->i_private;
 	}
 
 	if (!reg->show_ptdump_info)
@@ -239,15 +241,14 @@ static int kvm_ptdump_visitor(const struct kvm_pgtable_visit_ctx *ctx,
 	return 0;
 }
 
-static int kvm_ptdump_show(struct seq_file *m, void *)
+static int kvm_ptdump_show_common(struct seq_file *m,
+				  struct kvm_pgtable *pgtable)
 {
 	u64 ipa_size;
 	char ipa_description[32];
 	struct pg_state st;
 	struct addr_marker ipa_addr_markers[3] = {0};
 	struct pg_level pg_level_descr[KVM_PGTABLE_MAX_LEVELS] = {0};
-	struct kvm_pgtable_snapshot *snapshot = m->private;
-	struct kvm_pgtable *pgtable = &snapshot->pgtable;
 	struct kvm_pgtable_walker walker = (struct kvm_pgtable_walker) {
 		.cb	= kvm_ptdump_visitor,
 		.arg	= &st,
@@ -282,6 +283,26 @@ static int kvm_ptdump_show(struct seq_file *m, void *)
 	return kvm_pgtable_walk(pgtable, 0, ipa_size, &walker);
 }
 
+static int kvm_host_ptdump_show(struct seq_file *m, void *)
+{
+	struct kvm_pgtable_snapshot *snapshot = m->private;
+
+	return kvm_ptdump_show_common(m, &snapshot->pgtable);
+}
+
+static int kvm_ptdump_show(struct seq_file *m, void *)
+{
+	struct kvm *guest_kvm = m->private;
+	struct kvm_s2_mmu *mmu = &guest_kvm->arch.mmu;
+	int ret;
+
+	write_lock(&guest_kvm->mmu_lock);
+	ret = kvm_ptdump_show_common(m, mmu->pgt);
+	write_unlock(&guest_kvm->mmu_lock);
+
+	return ret;
+}
+
 static void kvm_ptdump_debugfs_register(struct kvm_ptdump_register *reg,
 					const char *name, struct dentry *parent)
 {
@@ -393,11 +414,19 @@ void kvm_ptdump_register_host(void)
 
 	host_reg.get_ptdump_info = kvm_host_get_ptdump_info;
 	host_reg.put_ptdump_info = kvm_host_put_ptdump_info;
+	host_reg.show_ptdump_info = kvm_host_ptdump_show;
 
 	kvm_ptdump_debugfs_register(&host_reg, "host_page_tables",
 				    kvm_debugfs_dir);
 }
 
+int kvm_ptdump_register_guest(struct kvm *kvm)
+{
+	debugfs_create_file("stage2_page_tables", 0400, kvm->debugfs_dentry,
+			    kvm, &kvm_ptdump_fops);
+	return 0;
+}
+
 static int __init kvm_host_ptdump_init(void)
 {
 	host_reg.priv = (void *)host_s2_pgtable_pages();
-- 
2.43.0.472.g3155946c3a-goog