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

From: Suravee Suthikulpanit
Date: Wed Mar 30 2016 - 06:00:25 EST

Hi Paolo,

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

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
audited the code to ensure that it is safe.


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.



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),
if (!kvm->buses[i])
goto out_err;
r = kvm_arch_init_vm(kvm, type);
if (r)
goto out_err;

Do you think that would be a problem?