Re: [PATCH v2 5/5] kvm, mem-hotplug: Do not pin apic access page in memory.

Tang Chen
2014-07-15T12:28:22Z

On 07/15/2014 08:09 PM, Gleb Natapov wrote:
> On Tue, Jul 15, 2014 at 01:52:40PM +0200, Jan Kiszka wrote:
......
>>
>> I cannot follow your concerns yet. Specifically, how should
>> APIC_ACCESS_ADDR (the VMCS field, right?) change while L2 is running? We
>> currently pin/unpin on L1->L2/L2->L1, respectively. Or what do you mean?
>>
> I am talking about this case:
> if (cpu_has_secondary_exec_ctrls()) {a
> } else {
> exec_control |=
> SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
> vmcs_write64(APIC_ACCESS_ADDR,
> page_to_phys(vcpu->kvm->arch.apic_access_page));
> }
> We do not pin here.
>

Hi Gleb,

7905 if (exec_control &
SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES) {
......
7912 if (vmx->nested.apic_access_page) /*
shouldn't happen */
7913
nested_release_page(vmx->nested.apic_access_page);
7914 vmx->nested.apic_access_page =
7915 nested_get_page(vcpu,
vmcs12->apic_access_addr);

I thought you were talking about the problem here. We pin
vmcs12->apic_access_addr
in memory. And I think we should do the same thing to this page as to L1
vm.
Right ?

......
7922 if (!vmx->nested.apic_access_page)
7923 exec_control &=
7924
~SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
7925 else
7926 vmcs_write64(APIC_ACCESS_ADDR,
7927
page_to_phys(vmx->nested.apic_access_page));
7928 } else if
(vm_need_virtualize_apic_accesses(vmx->vcpu.kvm)) {
7929 exec_control |=
7930
SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES;
7931 vmcs_write64(APIC_ACCESS_ADDR,
7932
page_to_phys(vcpu->kvm->arch.apic_access_page));
7933 }

And yes, we have the problem you said here. We can migrate the page
while L2 vm is running.
So I think we should enforce L2 vm to exit to L1. Right ?

Thanks.