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

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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: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240214131827.2856277-27-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Marc Zyngier 2024-02-14 13:18:27 +00:00 • committed by Oliver Upton
parent b80b701d5a
commit 891766581d
2 changed files with 84 additions and 0 deletions
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3
arch/arm64/include/asm/kvm_host.h
View file

@ -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;

81
arch/arm64/kvm/sys_regs.c
View file

@ -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);
}