[PATCH v2 11/11] arm64: ptdump: Add support for guest stage-2 pagetables dumping

Sebastian Ene
2023-10-19T14:41:56Z

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@google.com>
---
arch/arm64/include/asm/ptdump.h | 21 +++++++--
arch/arm64/kvm/mmu.c | 3 ++
arch/arm64/mm/ptdump.c | 84 +++++++++++++++++++++++++++++++++
arch/arm64/mm/ptdump_debugfs.c | 5 +-
4 files changed, 108 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
index 35b883524462..be86244d532b 100644
--- a/arch/arm64/include/asm/ptdump.h
+++ b/arch/arm64/include/asm/ptdump.h
@@ -5,6 +5,8 @@
#ifndef __ASM_PTDUMP_H
#define __ASM_PTDUMP_H

+#include <asm/kvm_pgtable.h>
+
#ifdef CONFIG_PTDUMP_CORE

#include <linux/mm_types.h>
@@ -30,14 +32,27 @@ struct ptdump_info {
void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
#ifdef CONFIG_PTDUMP_DEBUGFS
#define EFI_RUNTIME_MAP_END DEFAULT_MAP_WINDOW_64
-void __init ptdump_debugfs_register(struct ptdump_info *info, const char *name);
+struct dentry *ptdump_debugfs_register(struct ptdump_info *info,
+ const char *name);
#else
-static inline void ptdump_debugfs_register(struct ptdump_info *info,
- const char *name) { }
+static inline struct dentry *ptdump_debugfs_register(struct ptdump_info *info,
+ const char *name)
+{
+ return NULL;
+}
#endif
void ptdump_check_wx(void);
#endif /* CONFIG_PTDUMP_CORE */

+#ifdef CONFIG_NVHE_EL2_PTDUMP_DEBUGFS
+void ptdump_register_guest_stage2(struct kvm_pgtable *pgt, void *lock);
+void ptdump_unregister_guest_stage2(struct kvm_pgtable *pgt);
+#else
+static inline void ptdump_register_guest_stage2(struct kvm_pgtable *pgt,
+ void *lock) { }
+static inline void ptdump_unregister_guest_stage2(struct kvm_pgtable *pgt) { }
+#endif /* CONFIG_NVHE_EL2_PTDUMP_DEBUGFS */
+
#ifdef CONFIG_DEBUG_WX
#define debug_checkwx() ptdump_check_wx()
#else
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 482280fe22d7..e47988dba34d 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -11,6 +11,7 @@
#include <linux/sched/signal.h>
#include <trace/events/kvm.h>
#include <asm/pgalloc.h>
+#include <asm/ptdump.h>
#include <asm/cacheflush.h>
#include <asm/kvm_arm.h>
#include <asm/kvm_mmu.h>
@@ -908,6 +909,7 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t
if (err)
goto out_free_pgtable;

+ ptdump_register_guest_stage2(pgt, &kvm->mmu_lock);
mmu->last_vcpu_ran = alloc_percpu(typeof(*mmu->last_vcpu_ran));
if (!mmu->last_vcpu_ran) {
err = -ENOMEM;
@@ -1021,6 +1023,7 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
write_unlock(&kvm->mmu_lock);

if (pgt) {
+ ptdump_unregister_guest_stage2(pgt);
kvm_pgtable_stage2_destroy(pgt);
kfree(pgt);
}
diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index 4687840dcb69..facfb15468f5 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -26,6 +26,7 @@
#include <asm/ptdump.h>
#include <asm/kvm_pkvm.h>
#include <asm/kvm_pgtable.h>
+#include <asm/kvm_host.h>

enum address_markers_idx {
@@ -543,6 +544,22 @@ void ptdump_check_wx(void)
#ifdef CONFIG_NVHE_EL2_PTDUMP_DEBUGFS
static struct ptdump_info stage2_kernel_ptdump_info;

+#define GUEST_NAME_LEN (32U)
+
+struct ptdump_registered_guest {
+ struct list_head reg_list;
+ struct ptdump_info info;
+ struct mm_struct mem;
+ struct kvm_pgtable_snapshot snapshot;
+ struct dentry *dentry;
+ rwlock_t *lock;
+ char reg_name[GUEST_NAME_LEN];
+};
+
+static LIST_HEAD(ptdump_guest_list);
+static DEFINE_MUTEX(ptdump_list_lock);
+static u16 guest_no;
+
static phys_addr_t ptdump_host_pa(void *addr)
{
return __pa(addr);
@@ -740,6 +757,73 @@ static void stage2_ptdump_walk(struct seq_file *s, struct ptdump_info *info)

kvm_pgtable_walk(pgtable, start_ipa, end_ipa, &walker);
}
+
+static void guest_stage2_ptdump_walk(struct seq_file *s,
+ struct ptdump_info *info)
+{
+ struct kvm_pgtable_snapshot *snapshot = info->priv;
+ struct ptdump_registered_guest *guest;
+
+ guest = container_of(snapshot, struct ptdump_registered_guest,
+ snapshot);
+ read_lock(guest->lock);
+ stage2_ptdump_walk(s, info);
+ read_unlock(guest->lock);
+}
+
+void ptdump_register_guest_stage2(struct kvm_pgtable *pgt, void *lock)
+{
+ struct ptdump_registered_guest *guest;
+ struct dentry *d;
+
+ if (pgt == NULL || lock == NULL)
+ return;
+
+ guest = kzalloc(sizeof(struct ptdump_registered_guest), GFP_KERNEL);
+ if (!guest)
+ return;
+
+ memcpy(&guest->snapshot.pgtable, pgt, sizeof(struct kvm_pgtable));
+ guest->info = (struct ptdump_info) {
+ .ptdump_walk = guest_stage2_ptdump_walk,
+ .priv = &guest->snapshot
+ };
+
+ mutex_init(&guest->info.file_lock);
+ guest->lock = lock;
+ mutex_lock(&ptdump_list_lock);
+ snprintf(guest->reg_name, GUEST_NAME_LEN,
+ "%u_guest_stage2_page_tables", guest_no++);
+ d = ptdump_debugfs_register(&guest->info, guest->reg_name);
+ if (!d) {
+ mutex_unlock(&ptdump_list_lock);
+ goto free_entry;
+ }
+
+ guest->dentry = d;
+ list_add(&guest->reg_list, &ptdump_guest_list);
+ mutex_unlock(&ptdump_list_lock);
+ return;
+
+free_entry:
+ kfree(guest);
+}
+
+void ptdump_unregister_guest_stage2(struct kvm_pgtable *pgt)
+{
+ struct ptdump_registered_guest *guest;
+
+ mutex_lock(&ptdump_list_lock);
+ list_for_each_entry(guest, &ptdump_guest_list, reg_list) {
+ if (guest->snapshot.pgtable.pgd == pgt->pgd) {
+ list_del(&guest->reg_list);
+ debugfs_remove(guest->dentry);
+ kfree(guest);
+ break;
+ }
+ }
+ mutex_unlock(&ptdump_list_lock);
+}
#endif /* CONFIG_NVHE_EL2_PTDUMP_DEBUGFS */

static void __init ptdump_register_host_stage2(void)
diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
index 14619452dd8d..356753e27dee 100644
--- a/arch/arm64/mm/ptdump_debugfs.c
+++ b/arch/arm64/mm/ptdump_debugfs.c
@@ -49,7 +49,8 @@ static const struct file_operations ptdump_fops = {
.release = ptdump_release,
};

-void __init ptdump_debugfs_register(struct ptdump_info *info, const char *name)
+struct dentry *ptdump_debugfs_register(struct ptdump_info *info,
+ const char *name)
{
- debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
+ return debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
}
--
2.42.0.655.g421f12c284-goog