Commit 7c4f7354 authored by Sebastian Ene's avatar Sebastian Ene Committed by Marc Zyngier
Browse files

KVM: arm64: Register ptdump with debugfs on guest creation 



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.

[maz: moved function prototypes from kvm_host.h to kvm_mmu.h]

Signed-off-by: default avatarSebastian Ene <sebastianene@google.com>
Reviewed-by: default avatarVincent Donnefort <vdonnefort@google.com>
Link: https://lore.kernel.org/r/20240909124721.1672199-6-sebastianene@google.com


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 79c4c728

arch/arm64/include/asm/kvm_mmu.h

+6 −0
Original line number Diff line number Diff line
@@ -352,5 +352,11 @@ static inline bool kvm_is_nested_s2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu) 
	return &kvm->arch.mmu != mmu;

}



#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 /* __ASSEMBLY__ */

#endif /* __ARM64_KVM_MMU_H__ */

arch/arm64/kvm/Kconfig

+17 −0
Original line number Diff line number Diff line
@@ -65,4 +65,21 @@ 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

arch/arm64/kvm/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ 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

arch/arm64/kvm/arm.c

+1 −0
Original line number Diff line number Diff line
@@ -227,6 +227,7 @@ 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)

arch/arm64/kvm/ptdump.c

0 → 100644
+268 −0
Original line number Diff line number Diff line 
// 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@google.com>

 */

#include <linux/debugfs.h>

#include <linux/kvm_host.h>

#include <linux/seq_file.h>



#include <asm/kvm_mmu.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);

}