From: Wei-Lin Chang Date: Tue, 17 Mar 2026 18:26:38 +0000 (+0000) Subject: KVM: arm64: nv: Expose shadow page tables in debugfs X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=19e15dc73f0fc74eaf63ad9b3a50648450269b4d;p=thirdparty%2Fkernel%2Fstable.git KVM: arm64: nv: Expose shadow page tables in debugfs Exposing shadow page tables in debugfs improves the debugability and testability of NV. With this patch a new directory "nested" is created for each VM created if the host is NV capable. Within the directory each valid s2 mmu will have its shadow page table exposed as a readable file with the file name formatted as 0x-0x-s2-{en,dis}abled. The creation and removal of the files happen at the points when an s2 mmu becomes valid, or the context it represents change. In the future the "nested" directory can also hold other NV related information. This is gated behind CONFIG_PTDUMP_STAGE2_DEBUGFS. Suggested-by: Marc Zyngier Reviewed-by: Sebastian Ene Signed-off-by: Wei-Lin Chang Reviewed-by: Joey Gouly Link: https://patch.msgid.link/20260317182638.1592507-3-weilin.chang@arm.com [maz: minor refactor, full 16 chars addresses] Signed-off-by: Marc Zyngier --- diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 2ca264b3db5fa..70d9f6855cce3 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -217,6 +217,10 @@ 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. @@ -405,6 +409,11 @@ struct kvm_arch { * the associated pKVM instance in the hypervisor. */ struct kvm_protected_vm pkvm; + +#ifdef CONFIG_PTDUMP_STAGE2_DEBUGFS + /* 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 d968aca0461a2..01e9c72d6aa7a 100644 --- a/arch/arm64/include/asm/kvm_mmu.h +++ b/arch/arm64/include/asm/kvm_mmu.h @@ -393,8 +393,12 @@ 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 12c9f6e8dfdab..34bab84b18fe3 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -730,8 +730,10 @@ 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)) + if (kvm_s2_mmu_valid(s2_mmu)) { + kvm_nested_s2_ptdump_remove_debugfs(s2_mmu); s2_mmu->pending_unmap = true; + } /* * The virtual VMID (modulo CnP) will be used as a key when matching @@ -745,6 +747,8 @@ 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 8713001e992dd..f5753ac37a05c 100644 --- a/arch/arm64/kvm/ptdump.c +++ b/arch/arm64/kvm/ptdump.c @@ -10,12 +10,14 @@ #include #include +#include #include #include #include #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; @@ -277,6 +279,28 @@ 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, @@ -285,4 +309,6 @@ void kvm_s2_ptdump_create_debugfs(struct kvm *kvm) &kvm->arch.mmu, &kvm_pgtable_range_fops); debugfs_create_file("stage2_levels", 0400, kvm->debugfs_dentry, &kvm->arch.mmu, &kvm_pgtable_levels_fops); + if (cpus_have_final_cap(ARM64_HAS_NESTED_VIRT)) + kvm->arch.debugfs_nv_dentry = debugfs_create_dir("nested", kvm->debugfs_dentry); }