Hi Gleb, Paolo,
On 09/11/2014 10:47 PM, Gleb Natapov wrote:
On Thu, Sep 11, 2014 at 04:37:39PM +0200, Paolo Bonzini wrote:
Il 11/09/2014 16:31, Gleb Natapov ha scritto:
What if the page being swapped out is L1's APIC access page? We don't
run prepare_vmcs12 in that case because it's an L2->L0->L2 entry, so we
need to "do something".
We will do something on L2->L1 exit. We will call kvm_reload_apic_access_page().
That is what patch 5 of this series is doing.
Sorry, I meant "the APIC access page prepared by L1" for L2's execution.
You wrote:
if (!is_guest_mode() || !(vmcs12->secondary_vm_exec_control &
ECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES))
write(PIC_ACCESS_ADDR)
In other words if L2 shares L1 apic access page then reload, otherwise do
nothing.
but in that case you have to redo nested_get_page, so "do nothing"
doesn't work.
Ah, 7/7 is new in this submission. Before that this page was still
pinned. Looking at 7/7 now I do not see how it can work since it has no
code for mmu notifier to detect that it deals with such page and call
kvm_reload_apic_access_page().
Since L1 and L2 share one apic page, if the page is unmapped,
mmu_notifier will
be called, and :
- if vcpu is in L1, a L1->L0 exit is rised. apic page's pa will be
updated in the next
L0->L1 entry by making vcpu request.
- if vcpu is in L2 (is_guest_mode, right?), a L2->L0 exit is rised.
nested_vmx_vmexit()
will not be called since it is called in L2->L1 exit. It returns
from vmx_vcpu_run()
directly, right ? So we should update apic page in L0->L2 entry.
This is also done
by making vcpu request, right ?.
prepare_vmcs02() is called in L1->L2 entry, and nested_vmx_vmexit()
is called in
L2->L1 exit. So we also need to update L1's vmcs in
nested_vmx_vmexit() in patch 5/7.
IIUC, I think patch 1~6 has done such things.
And yes, the is_guest_mode() check is not needed.
I said to Tang previously that nested
kvm has a bunch of pinned page that are hard to deal with and suggested
to iron out non nested case first :(
Yes, and maybe adding patch 7 is not a good idea for now.
Thanks.
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