[PATCH v10 5/5] KVM: arm64: Register ptdump with debugfs on guest creation
Sebastian Ene
sebastianene at google.com
Mon Sep 9 05:47:21 PDT 2024
While arch/*/mem/ptdump handles the kernel pagetable dumping code,
introduce KVM/ptdump to show 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. Introduce the PTDUMP_STAGE2_DEBUGFS config.
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 at google.com>
Reviewed-by: Vincent Donnefort <vdonnefort at google.com>
---
arch/arm64/include/asm/kvm_host.h | 6 +
arch/arm64/kvm/Kconfig | 17 ++
arch/arm64/kvm/Makefile | 1 +
arch/arm64/kvm/arm.c | 1 +
arch/arm64/kvm/ptdump.c | 268 ++++++++++++++++++++++++++++++
5 files changed, 293 insertions(+)
create mode 100644 arch/arm64/kvm/ptdump.c
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index a33f5996ca9f..4acd589f086b 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -1473,4 +1473,10 @@ void kvm_set_vm_id_reg(struct kvm *kvm, u32 reg, u64 val);
(pa + pi + pa3) == 1; \
})
+#ifdef CONFIG_PTDUMP_STAGE2_DEBUGFS
+void kvm_s2_ptdump_create_debugfs(struct kvm *kvm);
+#else
+static inline void kvm_s2_ptdump_create_debugfs(struct kvm *kvm) {}
+#endif /* CONFIG_PTDUMP_STAGE2_DEBUGFS */
+
#endif /* __ARM64_KVM_HOST_H__ */
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 8304eb342be9..ead632ad01b4 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -66,4 +66,21 @@ 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 KVM
+ depends on DEBUG_KERNEL
+ depends on DEBUG_FS
+ depends on GENERIC_PTDUMP
+ select PTDUMP_CORE
+ 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 86a629aaf0a1..e4233b323a73 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile
@@ -27,6 +27,7 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \
kvm-$(CONFIG_HW_PERF_EVENTS) += pmu-emul.o pmu.o
kvm-$(CONFIG_ARM64_PTR_AUTH) += pauth.o
+kvm-$(CONFIG_PTDUMP_STAGE2_DEBUGFS) += ptdump.o
always-y := hyp_constants.h hyp-constants.s
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 9bef7638342e..b9fd928d3477 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -228,6 +228,7 @@ vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
void kvm_arch_create_vm_debugfs(struct kvm *kvm)
{
kvm_sys_regs_create_debugfs(kvm);
+ kvm_s2_ptdump_create_debugfs(kvm);
}
static void kvm_destroy_mpidr_data(struct kvm *kvm)
diff --git a/arch/arm64/kvm/ptdump.c b/arch/arm64/kvm/ptdump.c
new file mode 100644
index 000000000000..e29604a864b7
--- /dev/null
+++ b/arch/arm64/kvm/ptdump.c
@@ -0,0 +1,268 @@
+// 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, 2024
+ * Author: Sebastian Ene <sebastianene at google.com>
+ */
+#include <linux/debugfs.h>
+#include <linux/kvm_host.h>
+#include <linux/seq_file.h>
+
+#include <asm/kvm_host.h>
+#include <asm/kvm_pgtable.h>
+#include <asm/ptdump.h>
+
+#define MARKERS_LEN 2
+#define KVM_PGTABLE_MAX_LEVELS (KVM_PGTABLE_LAST_LEVEL + 1)
+
+struct kvm_ptdump_guest_state {
+ struct kvm *kvm;
+ struct ptdump_pg_state parser_state;
+ struct addr_marker ipa_marker[MARKERS_LEN];
+ struct ptdump_pg_level level[KVM_PGTABLE_MAX_LEVELS];
+ struct ptdump_range range[MARKERS_LEN];
+};
+
+static const struct ptdump_prot_bits stage2_pte_bits[] = {
+ {
+ .mask = PTE_VALID,
+ .val = PTE_VALID,
+ .set = " ",
+ .clear = "F",
+ }, {
+ .mask = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | PTE_VALID,
+ .val = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_R | PTE_VALID,
+ .set = "R",
+ .clear = " ",
+ }, {
+ .mask = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | PTE_VALID,
+ .val = KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W | PTE_VALID,
+ .set = "W",
+ .clear = " ",
+ }, {
+ .mask = KVM_PTE_LEAF_ATTR_HI_S2_XN | PTE_VALID,
+ .val = PTE_VALID,
+ .set = " ",
+ .clear = "X",
+ }, {
+ .mask = KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID,
+ .val = KVM_PTE_LEAF_ATTR_LO_S2_AF | PTE_VALID,
+ .set = "AF",
+ .clear = " ",
+ }, {
+ .mask = PTE_TABLE_BIT | PTE_VALID,
+ .val = PTE_VALID,
+ .set = "BLK",
+ .clear = " ",
+ },
+};
+
+static int kvm_ptdump_visitor(const struct kvm_pgtable_visit_ctx *ctx,
+ enum kvm_pgtable_walk_flags visit)
+{
+ struct ptdump_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_build_levels(struct ptdump_pg_level *level, u32 start_lvl)
+{
+ u32 i;
+ u64 mask;
+
+ if (WARN_ON_ONCE(start_lvl >= KVM_PGTABLE_LAST_LEVEL))
+ return -EINVAL;
+
+ mask = 0;
+ for (i = 0; i < ARRAY_SIZE(stage2_pte_bits); i++)
+ mask |= stage2_pte_bits[i].mask;
+
+ for (i = start_lvl; i < KVM_PGTABLE_MAX_LEVELS; i++) {
+ snprintf(level[i].name, sizeof(level[i].name), "%u", i);
+
+ level[i].num = ARRAY_SIZE(stage2_pte_bits);
+ level[i].bits = stage2_pte_bits;
+ level[i].mask = mask;
+ }
+
+ return 0;
+}
+
+static struct kvm_ptdump_guest_state *kvm_ptdump_parser_create(struct kvm *kvm)
+{
+ struct kvm_ptdump_guest_state *st;
+ struct kvm_s2_mmu *mmu = &kvm->arch.mmu;
+ struct kvm_pgtable *pgtable = mmu->pgt;
+ int ret;
+
+ st = kzalloc(sizeof(struct kvm_ptdump_guest_state), GFP_KERNEL_ACCOUNT);
+ if (!st)
+ return ERR_PTR(-ENOMEM);
+
+ ret = kvm_ptdump_build_levels(&st->level[0], pgtable->start_level);
+ if (ret) {
+ kfree(st);
+ return ERR_PTR(ret);
+ }
+
+ st->ipa_marker[0].name = "Guest IPA";
+ st->ipa_marker[1].start_address = BIT(pgtable->ia_bits);
+ st->range[0].end = BIT(pgtable->ia_bits);
+
+ st->kvm = kvm;
+ st->parser_state = (struct ptdump_pg_state) {
+ .marker = &st->ipa_marker[0],
+ .level = -1,
+ .pg_level = &st->level[0],
+ .ptdump.range = &st->range[0],
+ .start_address = 0,
+ };
+
+ return st;
+}
+
+static int kvm_ptdump_guest_show(struct seq_file *m, void *unused)
+{
+ int ret;
+ struct kvm_ptdump_guest_state *st = m->private;
+ struct kvm *kvm = st->kvm;
+ struct kvm_s2_mmu *mmu = &kvm->arch.mmu;
+ struct ptdump_pg_state *parser_state = &st->parser_state;
+ struct kvm_pgtable_walker walker = (struct kvm_pgtable_walker) {
+ .cb = kvm_ptdump_visitor,
+ .arg = parser_state,
+ .flags = KVM_PGTABLE_WALK_LEAF,
+ };
+
+ parser_state->seq = m;
+
+ write_lock(&kvm->mmu_lock);
+ ret = kvm_pgtable_walk(mmu->pgt, 0, BIT(mmu->pgt->ia_bits), &walker);
+ write_unlock(&kvm->mmu_lock);
+
+ return ret;
+}
+
+static int kvm_ptdump_guest_open(struct inode *m, struct file *file)
+{
+ struct kvm *kvm = m->i_private;
+ struct kvm_ptdump_guest_state *st;
+ int ret;
+
+ if (!kvm_get_kvm_safe(kvm))
+ return -ENOENT;
+
+ st = kvm_ptdump_parser_create(kvm);
+ if (IS_ERR(st)) {
+ ret = PTR_ERR(st);
+ goto err_with_kvm_ref;
+ }
+
+ ret = single_open(file, kvm_ptdump_guest_show, st);
+ if (!ret)
+ return 0;
+
+ kfree(st);
+err_with_kvm_ref:
+ kvm_put_kvm(kvm);
+ return ret;
+}
+
+static int kvm_ptdump_guest_close(struct inode *m, struct file *file)
+{
+ struct kvm *kvm = m->i_private;
+ void *st = ((struct seq_file *)file->private_data)->private;
+
+ kfree(st);
+ kvm_put_kvm(kvm);
+
+ return single_release(m, file);
+}
+
+static const struct file_operations kvm_ptdump_guest_fops = {
+ .open = kvm_ptdump_guest_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = kvm_ptdump_guest_close,
+};
+
+static int kvm_pgtable_range_show(struct seq_file *m, void *unused)
+{
+ struct kvm_pgtable *pgtable = m->private;
+
+ seq_printf(m, "%2u\n", pgtable->ia_bits);
+ return 0;
+}
+
+static int kvm_pgtable_levels_show(struct seq_file *m, void *unused)
+{
+ struct kvm_pgtable *pgtable = m->private;
+
+ seq_printf(m, "%1d\n", KVM_PGTABLE_MAX_LEVELS - pgtable->start_level);
+ return 0;
+}
+
+static int kvm_pgtable_debugfs_open(struct inode *m, struct file *file,
+ int (*show)(struct seq_file *, void *))
+{
+ struct kvm *kvm = m->i_private;
+ struct kvm_pgtable *pgtable;
+ int ret;
+
+ if (!kvm_get_kvm_safe(kvm))
+ return -ENOENT;
+
+ pgtable = kvm->arch.mmu.pgt;
+
+ ret = single_open(file, show, pgtable);
+ if (ret < 0)
+ kvm_put_kvm(kvm);
+ return ret;
+}
+
+static int kvm_pgtable_range_open(struct inode *m, struct file *file)
+{
+ return kvm_pgtable_debugfs_open(m, file, kvm_pgtable_range_show);
+}
+
+static int kvm_pgtable_levels_open(struct inode *m, struct file *file)
+{
+ return kvm_pgtable_debugfs_open(m, file, kvm_pgtable_levels_show);
+}
+
+static int kvm_pgtable_debugfs_close(struct inode *m, struct file *file)
+{
+ struct kvm *kvm = m->i_private;
+
+ kvm_put_kvm(kvm);
+ return single_release(m, file);
+}
+
+static const struct file_operations kvm_pgtable_range_fops = {
+ .open = kvm_pgtable_range_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = kvm_pgtable_debugfs_close,
+};
+
+static const struct file_operations kvm_pgtable_levels_fops = {
+ .open = kvm_pgtable_levels_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = kvm_pgtable_debugfs_close,
+};
+
+void kvm_s2_ptdump_create_debugfs(struct kvm *kvm)
+{
+ debugfs_create_file("stage2_page_tables", 0400, kvm->debugfs_dentry,
+ kvm, &kvm_ptdump_guest_fops);
+ debugfs_create_file("ipa_range", 0400, kvm->debugfs_dentry, kvm,
+ &kvm_pgtable_range_fops);
+ debugfs_create_file("stage2_levels", 0400, kvm->debugfs_dentry,
+ kvm, &kvm_pgtable_levels_fops);
+}
--
2.46.0.469.g59c65b2a67-goog
More information about the linux-arm-kernel
mailing list