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

From: Tang Chen
Date: Tue Jul 15 2014 - 08:32:08 EST

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 |=
We do not pin here.

Hi Gleb,

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 &=
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 |=
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 ?


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