[PATCHv3 2/2] kvm: retry nx_huge_page_recovery_thread creation
From: Keith Busch <hidden>
Date: 2025-02-27 23:06:39
Also in:
kvm, virtualization
Subsystem:
kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Sean Christopherson <seanjc@google.com> A VMM may send a signal to its threads while they've entered KVM_RUN. If that thread happens to be trying to make the huge page recovery vhost task, then it fails with -ERESTARTNOINTR. We need to retry if that happens, so call_once needs to be retryable. Make call_once complete only if what it called was successful. [implemented the kvm user side] Signed-off-by: Keith Busch <kbusch@kernel.org> --- arch/x86/kvm/mmu/mmu.c | 10 ++++------ include/linux/call_once.h | 16 +++++++++++----- 2 files changed, 15 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 18ca1ea6dc240..8160870398b90 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c@@ -7460,7 +7460,7 @@ static bool kvm_nx_huge_page_recovery_worker(void *data) return true; } -static void kvm_mmu_start_lpage_recovery(struct once *once) +static int kvm_mmu_start_lpage_recovery(struct once *once) { struct kvm_arch *ka = container_of(once, struct kvm_arch, nx_once); struct kvm *kvm = container_of(ka, struct kvm, arch);
@@ -7472,12 +7472,13 @@ static void kvm_mmu_start_lpage_recovery(struct once *once) kvm, "kvm-nx-lpage-recovery"); if (IS_ERR(nx_thread)) - return; + return PTR_ERR(nx_thread); vhost_task_start(nx_thread); /* Make the task visible only once it is fully started. */ WRITE_ONCE(kvm->arch.nx_huge_page_recovery_thread, nx_thread); + return 0; } int kvm_mmu_post_init_vm(struct kvm *kvm)
@@ -7485,10 +7486,7 @@ int kvm_mmu_post_init_vm(struct kvm *kvm) if (nx_hugepage_mitigation_hard_disabled) return 0; - call_once(&kvm->arch.nx_once, kvm_mmu_start_lpage_recovery); - if (!kvm->arch.nx_huge_page_recovery_thread) - return -ENOMEM; - return 0; + return call_once(&kvm->arch.nx_once, kvm_mmu_start_lpage_recovery); } void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
diff --git a/include/linux/call_once.h b/include/linux/call_once.h
index 6261aa0b3fb00..ddcfd91493eaa 100644
--- a/include/linux/call_once.h
+++ b/include/linux/call_once.h@@ -26,20 +26,26 @@ do { \ __once_init((once), #once, &__key); \ } while (0) -static inline void call_once(struct once *once, void (*cb)(struct once *)) +static inline int call_once(struct once *once, int (*cb)(struct once *)) { + int r; + /* Pairs with atomic_set_release() below. */ if (atomic_read_acquire(&once->state) == ONCE_COMPLETED) - return; + return 0; guard(mutex)(&once->lock); WARN_ON(atomic_read(&once->state) == ONCE_RUNNING); if (atomic_read(&once->state) != ONCE_NOT_STARTED) - return; + return -EINVAL; atomic_set(&once->state, ONCE_RUNNING); - cb(once); - atomic_set_release(&once->state, ONCE_COMPLETED); + r = cb(once); + if (r) + atomic_set(&once->state, ONCE_NOT_STARTED); + else + atomic_set_release(&once->state, ONCE_COMPLETED); + return r; } #endif /* _LINUX_CALL_ONCE_H */
--
2.43.5