Messages in this thread Patch in this message | | | Date | Wed, 7 Feb 2024 14:48:32 +0000 | Subject | [PATCH v5 3/4] KVM: arm64: Register ptdump with debugfs on guest creation | From | Sebastian Ene <> |
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While arch/*/mem/ptdump handles the kernel pagetable dumping code, introduce KVM/ptdump which shows 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 <sebastianene@google.com> --- arch/arm64/kvm/Kconfig | 13 ++++++ arch/arm64/kvm/Makefile | 1 + arch/arm64/kvm/debug.c | 7 ++++ arch/arm64/kvm/kvm_ptdump.h | 20 ++++++++++ arch/arm64/kvm/ptdump.c | 79 +++++++++++++++++++++++++++++++++++++ 5 files changed, 120 insertions(+) create mode 100644 arch/arm64/kvm/kvm_ptdump.h create mode 100644 arch/arm64/kvm/ptdump.c
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig index 6c3c8ca73e7f..28097dd72174 100644 --- a/arch/arm64/kvm/Kconfig +++ b/arch/arm64/kvm/Kconfig @@ -68,4 +68,17 @@ config PROTECTED_NVHE_STACKTRACE If unsure, or not using protected nVHE (pKVM), say N. +config PTDUMP_STAGE2_DEBUGFS + bool "Present the stage-2 pagetables to debugfs" + depends on PTDUMP_DEBUGFS && KVM + default n + help + Say Y here if you want to show the stage-2 kernel pagetables + layout in a debugfs file. This information is only useful for kernel developers + who are working in architecture specific areas of the kernel. + It is probably not a good idea to enable this feature in a production + kernel. + + If in doubt, say N. + endif # VIRTUALIZATION diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile index c0c050e53157..190eac17538c 100644 --- a/arch/arm64/kvm/Makefile +++ b/arch/arm64/kvm/Makefile @@ -23,6 +23,7 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \ vgic/vgic-its.o vgic/vgic-debug.o kvm-$(CONFIG_HW_PERF_EVENTS) += pmu-emul.o pmu.o +kvm-$(CONFIG_PTDUMP_STAGE2_DEBUGFS) += ptdump.o always-y := hyp_constants.h hyp-constants.s diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c index 8725291cb00a..aef52836cd90 100644 --- a/arch/arm64/kvm/debug.c +++ b/arch/arm64/kvm/debug.c @@ -14,6 +14,8 @@ #include <asm/kvm_arm.h> #include <asm/kvm_emulate.h> +#include <kvm_ptdump.h> + #include "trace.h" /* These are the bits of MDSCR_EL1 we may manipulate */ @@ -342,3 +344,8 @@ 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_guest_register(kvm); +} diff --git a/arch/arm64/kvm/kvm_ptdump.h b/arch/arm64/kvm/kvm_ptdump.h new file mode 100644 index 000000000000..a7c00a28481b --- /dev/null +++ b/arch/arm64/kvm/kvm_ptdump.h @@ -0,0 +1,20 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) Google, 2023 + * Author: Sebastian Ene <sebastianene@google.com> + */ + +#ifndef __KVM_PTDUMP_H +#define __KVM_PTDUMP_H + +#include <linux/kvm_host.h> +#include <asm/ptdump.h> + + +#ifdef CONFIG_PTDUMP_STAGE2_DEBUGFS +int kvm_ptdump_guest_register(struct kvm *kvm); +#else +static inline int kvm_ptdump_guest_register(struct kvm *kvm) { return 0; } +#endif /* CONFIG_PTDUMP_STAGE2_DEBUGFS */ + +#endif /* __KVM_PTDUMP_H */ diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c new file mode 100644 index 000000000000..a4e984da8aa7 --- /dev/null +++ b/arch/arm64/kvm/ptdump.c @@ -0,0 +1,79 @@ +// SPDX-License-Identifier: GPL-2.0-only +// +// Debug helper used to dump the stage-2 pagetables of the system and their +// associated permissions. +// +// Copyright (C) Google, 2023 +// Author: Sebastian Ene <sebastianene@google.com> + +#include <linux/debugfs.h> +#include <linux/kvm_host.h> +#include <linux/seq_file.h> + +#include <asm/kvm_pkvm.h> +#include <kvm_ptdump.h> + + +static int kvm_ptdump_guest_open(struct inode *inode, struct file *file); +static int kvm_ptdump_guest_show(struct seq_file *m, void *); + +static const struct file_operations kvm_ptdump_guest_fops = { + .open = kvm_ptdump_guest_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, +}; + +static int kvm_ptdump_guest_open(struct inode *inode, struct file *file) +{ + return single_open(file, kvm_ptdump_guest_show, inode->i_private); +} + +static int kvm_ptdump_visitor(const struct kvm_pgtable_visit_ctx *ctx, + enum kvm_pgtable_walk_flags visit) +{ + struct 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_show_common(struct seq_file *m, + struct kvm_pgtable *pgtable, + struct pg_state *parser_state) +{ + struct kvm_pgtable_walker walker = (struct kvm_pgtable_walker) { + .cb = kvm_ptdump_visitor, + .arg = parser_state, + .flags = KVM_PGTABLE_WALK_LEAF, + }; + + return kvm_pgtable_walk(pgtable, 0, BIT(pgtable->ia_bits), &walker); +} + +static int kvm_ptdump_guest_show(struct seq_file *m, void *) +{ + struct kvm *guest_kvm = m->private; + struct kvm_s2_mmu *mmu = &guest_kvm->arch.mmu; + struct pg_state parser_state = {0}; + int ret; + + write_lock(&guest_kvm->mmu_lock); + ret = kvm_ptdump_show_common(m, mmu->pgt, &parser_state); + write_unlock(&guest_kvm->mmu_lock); + + return ret; +} + +int kvm_ptdump_guest_register(struct kvm *kvm) +{ + struct dentry *parent; + + parent = debugfs_create_file("stage2_page_tables", 0400, + kvm->debugfs_dentry, kvm, + &kvm_ptdump_guest_fops); + if (IS_ERR(parent)) + return PTR_ERR(parent); + return 0; +} -- 2.43.0.594.gd9cf4e227d-goog
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