[PATCH v1 03/11] KVM: arm64: Use guard()/scoped_guard() in arm64 KVM EL1 code
Vincent Donnefort
vdonnefort at google.com
Mon Jun 15 05:59:10 PDT 2026
On Fri, Jun 12, 2026 at 07:59:17AM +0100, tabba at google.com wrote:
> Convert the manual mutex_lock()/spin_lock() pairs in
> arch/arm64/kvm/{pkvm,arm,mmu,reset,psci}.c to guard(mutex),
> guard(spinlock) and scoped_guard(), dropping unlock-only goto labels in
> favour of direct returns. Centralised cleanup gotos that still serve
> other resources are preserved.
>
> reset.c uses scoped_guard() rather than guard() so the lock covers only
> the small read/update window inside kvm_reset_vcpu(), leaving the rest
> of the function outside the critical section.
I believe in that case unless it really helps with cleaning resources, there's
not much point using scoped_guard().
I would keep it as is.
>
> Signed-off-by: Fuad Tabba <tabba at google.com>
> ---
> arch/arm64/kvm/arm.c | 14 +++-----
> arch/arm64/kvm/mmu.c | 80 +++++++++++++++---------------------------
> arch/arm64/kvm/pkvm.c | 26 ++++++--------
> arch/arm64/kvm/psci.c | 17 ++++-----
> arch/arm64/kvm/reset.c | 8 ++---
> 5 files changed, 53 insertions(+), 92 deletions(-)
>
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 9453321ef8c6..c9f36932c980 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -793,9 +793,7 @@ int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
> int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
> struct kvm_mp_state *mp_state)
> {
> - int ret = 0;
> -
> - spin_lock(&vcpu->arch.mp_state_lock);
> + guard(spinlock)(&vcpu->arch.mp_state_lock);
>
> switch (mp_state->mp_state) {
> case KVM_MP_STATE_RUNNABLE:
> @@ -808,12 +806,10 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
> kvm_arm_vcpu_suspend(vcpu);
> break;
> default:
> - ret = -EINVAL;
> + return -EINVAL;
> }
>
> - spin_unlock(&vcpu->arch.mp_state_lock);
> -
> - return ret;
> + return 0;
> }
>
> /**
> @@ -1726,15 +1722,13 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
> /*
> * Handle the "start in power-off" case.
> */
> - spin_lock(&vcpu->arch.mp_state_lock);
> + guard(spinlock)(&vcpu->arch.mp_state_lock);
>
> if (power_off)
> __kvm_arm_vcpu_power_off(vcpu);
> else
> WRITE_ONCE(vcpu->arch.mp_state.mp_state, KVM_MP_STATE_RUNNABLE);
>
> - spin_unlock(&vcpu->arch.mp_state_lock);
> -
> return 0;
> }
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 4da9281312eb..d18f4ce7ceae 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -391,13 +391,13 @@ static void stage2_flush_vm(struct kvm *kvm)
> */
> void __init free_hyp_pgds(void)
> {
> - mutex_lock(&kvm_hyp_pgd_mutex);
> - if (hyp_pgtable) {
> - kvm_pgtable_hyp_destroy(hyp_pgtable);
> - kfree(hyp_pgtable);
> - hyp_pgtable = NULL;
> - }
> - mutex_unlock(&kvm_hyp_pgd_mutex);
> + guard(mutex)(&kvm_hyp_pgd_mutex);
> + if (!hyp_pgtable)
> + return;
> +
> + kvm_pgtable_hyp_destroy(hyp_pgtable);
> + kfree(hyp_pgtable);
> + hyp_pgtable = NULL;
> }
>
> static bool kvm_host_owns_hyp_mappings(void)
> @@ -424,16 +424,11 @@ static bool kvm_host_owns_hyp_mappings(void)
> int __create_hyp_mappings(unsigned long start, unsigned long size,
> unsigned long phys, enum kvm_pgtable_prot prot)
> {
> - int err;
> -
> if (WARN_ON(!kvm_host_owns_hyp_mappings()))
> return -EINVAL;
>
> - mutex_lock(&kvm_hyp_pgd_mutex);
> - err = kvm_pgtable_hyp_map(hyp_pgtable, start, size, phys, prot);
> - mutex_unlock(&kvm_hyp_pgd_mutex);
> -
> - return err;
> + guard(mutex)(&kvm_hyp_pgd_mutex);
> + return kvm_pgtable_hyp_map(hyp_pgtable, start, size, phys, prot);
> }
>
> static phys_addr_t kvm_kaddr_to_phys(void *kaddr)
> @@ -481,56 +476,42 @@ static int share_pfn_hyp(u64 pfn)
> {
> struct rb_node **node, *parent;
> struct hyp_shared_pfn *this;
> - int ret = 0;
>
> - mutex_lock(&hyp_shared_pfns_lock);
> + guard(mutex)(&hyp_shared_pfns_lock);
> this = find_shared_pfn(pfn, &node, &parent);
> if (this) {
> this->count++;
> - goto unlock;
> + return 0;
> }
>
> this = kzalloc_obj(*this);
> - if (!this) {
> - ret = -ENOMEM;
> - goto unlock;
> - }
> + if (!this)
> + return -ENOMEM;
>
> this->pfn = pfn;
> this->count = 1;
> rb_link_node(&this->node, parent, node);
> rb_insert_color(&this->node, &hyp_shared_pfns);
> - ret = kvm_call_hyp_nvhe(__pkvm_host_share_hyp, pfn);
> -unlock:
> - mutex_unlock(&hyp_shared_pfns_lock);
> -
> - return ret;
> + return kvm_call_hyp_nvhe(__pkvm_host_share_hyp, pfn);
> }
>
> static int unshare_pfn_hyp(u64 pfn)
> {
> struct rb_node **node, *parent;
> struct hyp_shared_pfn *this;
> - int ret = 0;
>
> - mutex_lock(&hyp_shared_pfns_lock);
> + guard(mutex)(&hyp_shared_pfns_lock);
> this = find_shared_pfn(pfn, &node, &parent);
> - if (WARN_ON(!this)) {
> - ret = -ENOENT;
> - goto unlock;
> - }
> + if (WARN_ON(!this))
> + return -ENOENT;
>
> this->count--;
> if (this->count)
> - goto unlock;
> + return 0;
>
> rb_erase(&this->node, &hyp_shared_pfns);
> kfree(this);
> - ret = kvm_call_hyp_nvhe(__pkvm_host_unshare_hyp, pfn);
> -unlock:
> - mutex_unlock(&hyp_shared_pfns_lock);
> -
> - return ret;
> + return kvm_call_hyp_nvhe(__pkvm_host_unshare_hyp, pfn);
> }
>
> int kvm_share_hyp(void *from, void *to)
> @@ -655,7 +636,7 @@ int hyp_alloc_private_va_range(size_t size, unsigned long *haddr)
> unsigned long base;
> int ret = 0;
>
> - mutex_lock(&kvm_hyp_pgd_mutex);
> + guard(mutex)(&kvm_hyp_pgd_mutex);
>
> /*
> * This assumes that we have enough space below the idmap
> @@ -670,8 +651,6 @@ int hyp_alloc_private_va_range(size_t size, unsigned long *haddr)
> base = io_map_base - size;
> ret = __hyp_alloc_private_va_range(base);
>
> - mutex_unlock(&kvm_hyp_pgd_mutex);
> -
> if (!ret)
> *haddr = base;
>
> @@ -714,17 +693,16 @@ int create_hyp_stack(phys_addr_t phys_addr, unsigned long *haddr)
> size_t size;
> int ret;
>
> - mutex_lock(&kvm_hyp_pgd_mutex);
> - /*
> - * Efficient stack verification using the NVHE_STACK_SHIFT bit implies
> - * an alignment of our allocation on the order of the size.
> - */
> - size = NVHE_STACK_SIZE * 2;
> - base = ALIGN_DOWN(io_map_base - size, size);
> + scoped_guard(mutex, &kvm_hyp_pgd_mutex) {
> + /*
> + * Efficient stack verification using the NVHE_STACK_SHIFT bit implies
> + * an alignment of our allocation on the order of the size.
> + */
> + size = NVHE_STACK_SIZE * 2;
> + base = ALIGN_DOWN(io_map_base - size, size);
>
> - ret = __hyp_alloc_private_va_range(base);
> -
> - mutex_unlock(&kvm_hyp_pgd_mutex);
> + ret = __hyp_alloc_private_va_range(base);
> + }
Not sure about that one, it's not shorter, doesn't remove any label but add
a tab.
>
> if (ret) {
> kvm_err("Cannot allocate hyp stack guard page\n");
> diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c
> index 053e4f733e4b..a39111b70f9f 100644
> --- a/arch/arm64/kvm/pkvm.c
> +++ b/arch/arm64/kvm/pkvm.c
> @@ -190,39 +190,33 @@ bool pkvm_hyp_vm_is_created(struct kvm *kvm)
>
> int pkvm_create_hyp_vm(struct kvm *kvm)
> {
> - int ret = 0;
> -
> /*
> * Synchronise with kvm_arch_prepare_memory_region(), as we
> * prevent memslot modifications on a pVM that has been run.
> */
> - mutex_lock(&kvm->slots_lock);
> - mutex_lock(&kvm->arch.config_lock);
> - if (!pkvm_hyp_vm_is_created(kvm))
> - ret = __pkvm_create_hyp_vm(kvm);
> - mutex_unlock(&kvm->arch.config_lock);
> - mutex_unlock(&kvm->slots_lock);
> + guard(mutex)(&kvm->slots_lock);
> + guard(mutex)(&kvm->arch.config_lock);
>
> - return ret;
> + if (!pkvm_hyp_vm_is_created(kvm))
> + return __pkvm_create_hyp_vm(kvm);
> +
> + return 0;
> }
>
> int pkvm_create_hyp_vcpu(struct kvm_vcpu *vcpu)
> {
> - int ret = 0;
> + guard(mutex)(&vcpu->kvm->arch.config_lock);
>
> - mutex_lock(&vcpu->kvm->arch.config_lock);
> if (!vcpu_get_flag(vcpu, VCPU_PKVM_FINALIZED))
> - ret = __pkvm_create_hyp_vcpu(vcpu);
> - mutex_unlock(&vcpu->kvm->arch.config_lock);
> + return __pkvm_create_hyp_vcpu(vcpu);
>
> - return ret;
> + return 0;
> }
>
> void pkvm_destroy_hyp_vm(struct kvm *kvm)
> {
> - mutex_lock(&kvm->arch.config_lock);
> + guard(mutex)(&kvm->arch.config_lock);
> __pkvm_destroy_hyp_vm(kvm);
> - mutex_unlock(&kvm->arch.config_lock);
> }
>
> int pkvm_init_host_vm(struct kvm *kvm, unsigned long type)
> diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
> index 3b5dbe9a0a0e..e1389c525e9d 100644
> --- a/arch/arm64/kvm/psci.c
> +++ b/arch/arm64/kvm/psci.c
> @@ -62,7 +62,6 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
> struct vcpu_reset_state *reset_state;
> struct kvm *kvm = source_vcpu->kvm;
> struct kvm_vcpu *vcpu = NULL;
> - int ret = PSCI_RET_SUCCESS;
> unsigned long cpu_id;
>
> cpu_id = smccc_get_arg1(source_vcpu);
> @@ -78,14 +77,13 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
> if (!vcpu)
> return PSCI_RET_INVALID_PARAMS;
>
> - spin_lock(&vcpu->arch.mp_state_lock);
> + guard(spinlock)(&vcpu->arch.mp_state_lock);
> +
> if (!kvm_arm_vcpu_stopped(vcpu)) {
> if (kvm_psci_version(source_vcpu) != KVM_ARM_PSCI_0_1)
> - ret = PSCI_RET_ALREADY_ON;
> + return PSCI_RET_ALREADY_ON;
> else
> - ret = PSCI_RET_INVALID_PARAMS;
> -
> - goto out_unlock;
> + return PSCI_RET_INVALID_PARAMS;
> }
>
> reset_state = &vcpu->arch.reset_state;
> @@ -113,9 +111,7 @@ static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
> WRITE_ONCE(vcpu->arch.mp_state.mp_state, KVM_MP_STATE_RUNNABLE);
> kvm_vcpu_wake_up(vcpu);
>
> -out_unlock:
> - spin_unlock(&vcpu->arch.mp_state_lock);
> - return ret;
> + return PSCI_RET_SUCCESS;
> }
>
> static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
> @@ -176,9 +172,8 @@ static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type, u64 flags)
> * re-initialized.
> */
> kvm_for_each_vcpu(i, tmp, vcpu->kvm) {
> - spin_lock(&tmp->arch.mp_state_lock);
> + guard(spinlock)(&tmp->arch.mp_state_lock);
> WRITE_ONCE(tmp->arch.mp_state.mp_state, KVM_MP_STATE_STOPPED);
> - spin_unlock(&tmp->arch.mp_state_lock);
> }
> kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_SLEEP);
>
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index b963fd975aac..60969d90bdd3 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -193,10 +193,10 @@ void kvm_reset_vcpu(struct kvm_vcpu *vcpu)
> bool loaded;
> u32 pstate;
>
> - spin_lock(&vcpu->arch.mp_state_lock);
> - reset_state = vcpu->arch.reset_state;
> - vcpu->arch.reset_state.reset = false;
> - spin_unlock(&vcpu->arch.mp_state_lock);
> + scoped_guard(spinlock, &vcpu->arch.mp_state_lock) {
> + reset_state = vcpu->arch.reset_state;
> + vcpu->arch.reset_state.reset = false;
> + }
Same, I don't find this one really interesting.
>
> preempt_disable();
> loaded = (vcpu->cpu != -1);
> --
> 2.54.0.1136.gdb2ca164c4-goog
>
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