[PATCH v2 1/6] KVM: arm64: ptdump: Remove shadow ptdump files

[Wei-Lin Chang]

Previously we exposed shadow page tables by creating a debugfs ptdump
file whenever a nested mmu instance gets bound to a new context, and
deleting the debugfs file whose context was getting unbound.

This turned out to be buggy, as the instance<->context binding process
is done with the mmu_lock held, and debugfs creation/deletion can sleep.

Revert most of commit 19e15dc73f0f ("KVM: arm64: nv: Expose shadow page
tables in debugfs"), keep the "nested" debugfs directory for use in a
later patch where we'll expose the shadow ptdump in another way.

Fixes: 19e15dc73f0f ("KVM: arm64: nv: Expose shadow page tables in debugfs")
Reported-by: Itaru Kitayama <itaru.kitayama at fujitsu.com>
Closes: https://lore.kernel.org/kvmarm/aiuF0KSvvv-ZozI1@sm-arm-grace07/
Signed-off-by: Wei-Lin Chang <weilin.chang at arm.com>
---
 arch/arm64/include/asm/kvm_host.h |  5 +----
 arch/arm64/include/asm/kvm_mmu.h  |  4 ----
 arch/arm64/kvm/nested.c           |  6 +-----
 arch/arm64/kvm/ptdump.c           | 23 -----------------------
 4 files changed, 2 insertions(+), 36 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 2faa60df847d..94bced53a323 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -217,10 +217,6 @@ struct kvm_s2_mmu {
 	 */
 	bool	nested_stage2_enabled;
 
-#ifdef CONFIG_PTDUMP_STAGE2_DEBUGFS
-	struct dentry *shadow_pt_debugfs_dentry;
-#endif
-
 	/*
 	 * true when this MMU needs to be unmapped before being used for a new
 	 * purpose.
@@ -424,6 +420,7 @@ struct kvm_arch {
 	/* Nested virtualization info */
 	struct dentry *debugfs_nv_dentry;
 #endif
+
 };
 
 struct kvm_vcpu_fault_info {
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 6eae7e7e2a68..c1e535e3d931 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -392,12 +392,8 @@ static inline bool kvm_supports_cacheable_pfnmap(void)
 
 #ifdef CONFIG_PTDUMP_STAGE2_DEBUGFS
 void kvm_s2_ptdump_create_debugfs(struct kvm *kvm);
-void kvm_nested_s2_ptdump_create_debugfs(struct kvm_s2_mmu *mmu);
-void kvm_nested_s2_ptdump_remove_debugfs(struct kvm_s2_mmu *mmu);
 #else
 static inline void kvm_s2_ptdump_create_debugfs(struct kvm *kvm) {}
-static inline void kvm_nested_s2_ptdump_create_debugfs(struct kvm_s2_mmu *mmu) {}
-static inline void kvm_nested_s2_ptdump_remove_debugfs(struct kvm_s2_mmu *mmu) {}
 #endif /* CONFIG_PTDUMP_STAGE2_DEBUGFS */
 
 #endif /* __ASSEMBLER__ */
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index faa4a48f265d..6435efd65cb5 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -834,10 +834,8 @@ static struct kvm_s2_mmu *get_s2_mmu_nested(struct kvm_vcpu *vcpu)
 	kvm->arch.nested_mmus_next = (i + 1) % kvm->arch.nested_mmus_size;
 
 	/* Make sure we don't forget to do the laundry */
-	if (kvm_s2_mmu_valid(s2_mmu)) {
-		kvm_nested_s2_ptdump_remove_debugfs(s2_mmu);
+	if (kvm_s2_mmu_valid(s2_mmu))
 		s2_mmu->pending_unmap = true;
-	}
 
 	/*
 	 * The virtual VMID (modulo CnP) will be used as a key when matching
@@ -851,8 +849,6 @@ static struct kvm_s2_mmu *get_s2_mmu_nested(struct kvm_vcpu *vcpu)
 	s2_mmu->tlb_vtcr = vcpu_read_sys_reg(vcpu, VTCR_EL2);
 	s2_mmu->nested_stage2_enabled = vcpu_read_sys_reg(vcpu, HCR_EL2) & HCR_VM;
 
-	kvm_nested_s2_ptdump_create_debugfs(s2_mmu);
-
 out:
 	atomic_inc(&s2_mmu->refcnt);
 
diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
index c9140e22abcf..7c32f1f7772c 100644
--- a/arch/arm64/kvm/ptdump.c
+++ b/arch/arm64/kvm/ptdump.c
@@ -17,7 +17,6 @@
 
 #define MARKERS_LEN		2
 #define KVM_PGTABLE_MAX_LEVELS	(KVM_PGTABLE_LAST_LEVEL + 1)
-#define S2FNAMESZ		sizeof("0x0123456789abcdef-0x0123456789abcdef-s2-disabled")
 
 struct kvm_ptdump_guest_state {
 	struct kvm_s2_mmu	*mmu;
@@ -273,28 +272,6 @@ static const struct file_operations kvm_pgtable_levels_fops = {
 	.release	= kvm_pgtable_debugfs_close,
 };
 
-void kvm_nested_s2_ptdump_create_debugfs(struct kvm_s2_mmu *mmu)
-{
-	struct dentry *dent;
-	char file_name[S2FNAMESZ];
-
-	snprintf(file_name, sizeof(file_name), "0x%016llx-0x%016llx-s2-%sabled",
-		 mmu->tlb_vttbr,
-		 mmu->tlb_vtcr,
-		 mmu->nested_stage2_enabled ? "en" : "dis");
-
-	dent = debugfs_create_file(file_name, 0400,
-				   mmu->arch->debugfs_nv_dentry, mmu,
-				   &kvm_ptdump_guest_fops);
-
-	mmu->shadow_pt_debugfs_dentry = dent;
-}
-
-void kvm_nested_s2_ptdump_remove_debugfs(struct kvm_s2_mmu *mmu)
-{
-	debugfs_remove(mmu->shadow_pt_debugfs_dentry);
-}
-
 void kvm_s2_ptdump_create_debugfs(struct kvm *kvm)
 {
 	debugfs_create_file("stage2_page_tables", 0400, kvm->debugfs_dentry,
-- 
2.43.0