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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/13/25 16:35, Keith Busch wrote: >> Ok, I found the code and it doesn't exec (e.g. >> https://github.com/google/crosvm/blob/b339d3d7/src/crosvm/sys/linux/jail_warden.rs#L122), >> so that's not an option. Well, if I understand correctly from a >> cursory look at the code, crosvm is creating a jailed child process >> early, and then spawns further jails through it; so it's just this >> first process that has to cheat. >> >> One possibility on the KVM side is to delay creating the vhost_task >> until the first KVM_RUN. I don't like it but... > > This option is actually kind of appealing in that we don't need to > change any application side to filter out kernel tasks, as well as not > having a new kernel dependency to even report these types of tasks as > kernel threads. > > I gave it a quick try. I'm not very familiar with the code here, so not > sure if this is thread safe or not, but it did successfully get crosvm > booting again. That looks good to me too. Would you like to send it with a commit message and SoB? Thanks, Paolo > --- > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 2401606db2604..422b6b06de4fe 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -7415,6 +7415,8 @@ int kvm_mmu_post_init_vm(struct kvm *kvm) > { > if (nx_hugepage_mitigation_hard_disabled) > return 0; > + if (kvm->arch.nx_huge_page_recovery_thread) > + return 0; > > kvm->arch.nx_huge_page_last = get_jiffies_64(); > kvm->arch.nx_huge_page_recovery_thread = vhost_task_create( > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index c79a8cc57ba42..263363c46626b 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -11463,6 +11463,10 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu) > struct kvm_run *kvm_run = vcpu->run; > int r; > > + r = kvm_mmu_post_init_vm(vcpu->kvm); > + if (r) > + return r; > + > vcpu_load(vcpu); > kvm_sigset_activate(vcpu); > kvm_run->flags = 0; > @@ -12740,11 +12744,6 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) > return ret; > } > > -int kvm_arch_post_init_vm(struct kvm *kvm) > -{ > - return kvm_mmu_post_init_vm(kvm); > -} > - > static void kvm_unload_vcpu_mmu(struct kvm_vcpu *vcpu) > { > vcpu_load(vcpu); > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 401439bb21e3e..a219bd2d8aec8 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -1596,7 +1596,6 @@ int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu); > bool kvm_arch_dy_runnable(struct kvm_vcpu *vcpu); > bool kvm_arch_dy_has_pending_interrupt(struct kvm_vcpu *vcpu); > bool kvm_arch_vcpu_preempted_in_kernel(struct kvm_vcpu *vcpu); > -int kvm_arch_post_init_vm(struct kvm *kvm); > void kvm_arch_pre_destroy_vm(struct kvm *kvm); > void kvm_arch_create_vm_debugfs(struct kvm *kvm); > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index de2c11dae2316..adacc6eaa7d9d 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1065,15 +1065,6 @@ static int kvm_create_vm_debugfs(struct kvm *kvm, const char *fdname) > return ret; > } > > -/* > - * Called after the VM is otherwise initialized, but just before adding it to > - * the vm_list. > - */ > -int __weak kvm_arch_post_init_vm(struct kvm *kvm) > -{ > - return 0; > -} > - > /* > * Called just after removing the VM from the vm_list, but before doing any > * other destruction. > @@ -1194,10 +1185,6 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname) > if (r) > goto out_err_no_debugfs; > > - r = kvm_arch_post_init_vm(kvm); > - if (r) > - goto out_err; > - > mutex_lock(&kvm_lock); > list_add(&kvm->vm_list, &vm_list); > mutex_unlock(&kvm_lock); > @@ -1207,8 +1194,6 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname) > > return kvm; > > -out_err: > - kvm_destroy_vm_debugfs(kvm); > out_err_no_debugfs: > kvm_coalesced_mmio_free(kvm); > out_no_coalesced_mmio: > -- >