Commit 89176658 authored by Marc Zyngier's avatar Marc Zyngier Committed by Oliver Upton
Browse files

KVM: arm64: Add debugfs file for guest's ID registers 



Debugging ID register setup can be a complicated affair. Give the
kernel hacker a way to dump that state in an easy to parse way.

Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240214131827.2856277-27-maz@kernel.org


Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
parent b80b701d

arch/arm64/include/asm/kvm_host.h

+3 −0
Original line number Diff line number Diff line
@@ -319,6 +319,9 @@ struct kvm_arch { 
	/* PMCR_EL0.N value for the guest */

	u8 pmcr_n;



	/* Iterator for idreg debugfs */

	u8	idreg_debugfs_iter;



	/* Hypercall features firmware registers' descriptor */

	struct kvm_smccc_features smccc_feat;

	struct maple_tree smccc_filter;

arch/arm64/kvm/sys_regs.c

+81 −0
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include <linux/bitfield.h>

#include <linux/bsearch.h>

#include <linux/cacheinfo.h>

#include <linux/debugfs.h>

#include <linux/kvm_host.h>

#include <linux/mm.h>

#include <linux/printk.h>
@@ -3422,6 +3423,81 @@ static bool emulate_sys_reg(struct kvm_vcpu *vcpu, 
	return false;

}



static void *idregs_debug_start(struct seq_file *s, loff_t *pos)

{

	struct kvm *kvm = s->private;

	u8 *iter;



	mutex_lock(&kvm->arch.config_lock);



	iter = &kvm->arch.idreg_debugfs_iter;

	if (*iter == (u8)~0) {

		*iter = *pos;

		if (*iter >= KVM_ARM_ID_REG_NUM)

			iter = NULL;

	} else {

		iter = ERR_PTR(-EBUSY);

	}



	mutex_unlock(&kvm->arch.config_lock);



	return iter;

}



static void *idregs_debug_next(struct seq_file *s, void *v, loff_t *pos)

{

	struct kvm *kvm = s->private;



	(*pos)++;



	if ((kvm->arch.idreg_debugfs_iter + 1) < KVM_ARM_ID_REG_NUM) {

		kvm->arch.idreg_debugfs_iter++;



		return &kvm->arch.idreg_debugfs_iter;

	}



	return NULL;

}



static void idregs_debug_stop(struct seq_file *s, void *v)

{

	struct kvm *kvm = s->private;



	if (IS_ERR(v))

		return;



	mutex_lock(&kvm->arch.config_lock);



	kvm->arch.idreg_debugfs_iter = ~0;



	mutex_unlock(&kvm->arch.config_lock);

}



static int idregs_debug_show(struct seq_file *s, void *v)

{

	struct kvm *kvm = s->private;

	const struct sys_reg_desc *desc;



	desc = first_idreg + kvm->arch.idreg_debugfs_iter;



	if (!desc->name)

		return 0;



	seq_printf(s, "%20s:\t%016llx\n",

		   desc->name, IDREG(kvm, IDX_IDREG(kvm->arch.idreg_debugfs_iter)));



	return 0;

}



static const struct seq_operations idregs_debug_sops = {

	.start	= idregs_debug_start,

	.next	= idregs_debug_next,

	.stop	= idregs_debug_stop,

	.show	= idregs_debug_show,

};



DEFINE_SEQ_ATTRIBUTE(idregs_debug);



static void kvm_reset_id_regs(struct kvm_vcpu *vcpu)

{

	const struct sys_reg_desc *idreg = first_idreg;
@@ -3441,6 +3517,11 @@ static void kvm_reset_id_regs(struct kvm_vcpu *vcpu) 
		id = reg_to_encoding(idreg);

	}



	kvm->arch.idreg_debugfs_iter = ~0;



	debugfs_create_file("idregs", 0444, kvm->debugfs_dentry, kvm,

			    &idregs_debug_fops);



	set_bit(KVM_ARCH_FLAG_ID_REGS_INITIALIZED, &kvm->arch.flags);

}