Re: [PART1 RFC v3 02/12] KVM: x86: Introducing kvm_x86_ops VM init/uninit hooks

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Hi Paolo,

On 3/30/16 19:07, Paolo Bonzini wrote:


On 30/03/2016 12:00, Suravee Suthikulpanit wrote:
Hi Paolo,

On 3/29/16 18:47, Suravee Suthikulpanit wrote:
Hi,

On 03/29/2016 05:21 PM, Paolo Bonzini wrote:


On 29/03/2016 07:27, Suravee Suthikulpanit wrote:

Adding function pointers in struct kvm_x86_ops for
processor-specific
layer to provide hooks for when KVM initialize and un-initialize VM.
This is not the only thing your patch is doing, and the "other" change
definitely needs a lot more explanation about why you did it and how
you
audited the code to ensure that it is safe.

Paolo


Sorry, for not mentioning this earlier. I am moving the
kvm_arch_init_vm() call mainly to go after mutex_init(&kvm->slots_lock)
since I am calling the x86_set_memory_region() (which uses slots_lock)
in the vm_init() hooks (for AVIC initialization).

Lemme re-check if this would be safe for other code.

No problem.  In the meanwhile a patch got in ("KVM: fix spin_lock_init
order on x86") that should help you.

Thanks,

Paolo


Right.... that's just what I need :) I'll re-base to the latest tip then.

Actually, in the file virt/kvm/kvm_main.c, I still need to move the
kvm_arch_init_vm() to some place after the call to kvm_alloc_memslots()
since I am calling x86_set_memory_region() in the vm_init hook.

         r = -ENOMEM;
         for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
                 kvm->memslots[i] = kvm_alloc_memslots();
                 if (!kvm->memslots[i])
                         goto out_err_no_srcu;
         }

         if (init_srcu_struct(&kvm->srcu))
                 goto out_err_no_srcu;
         if (init_srcu_struct(&kvm->irq_srcu))
                 goto out_err_no_irq_srcu;
         for (i = 0; i < KVM_NR_BUSES; i++) {
                 kvm->buses[i] = kzalloc(sizeof(struct kvm_io_bus),
                                         GFP_KERNEL);
                 if (!kvm->buses[i])
                         goto out_err;
         }
//HERE
         r = kvm_arch_init_vm(kvm, type);
         if (r)
                 goto out_err;

Do you think that would be a problem?

Can you delay that to after the creation of the first VCPU?

Sure, I can. That's what I was doing originally before we introduce the vm_init hook. I just thought that this would make a nice place.

Allocating AVIC data structures is not required if userspace has not
called KVM_CREATE_IRQCHIP or enabled KVM_CAP_SPLIT_IRQCHIP.

Paolo


Okay.

Thanks,
Suravee
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