On 2014-03-20 21:58, Bandan Das wrote:
> Jan Kiszka <jan.kiszka@xxxxxxxxxxx> writes:
>
>> On 2014-03-20 04:28, Bandan Das wrote:
>>> Some L1 hypervisors such as Xen seem to be calling invept after
>>> vmclear or before vmptrld on L2. In this case, proceed with
>>> falling through and syncing roots as a case where
>>> context wide invalidation can't be supported
>>
>> Can we also base this behaviour on a statement in the SDM? But on first
>> glance, I do not find anything like this over there.
>
> The SDM has nothing of this sort explicitly mentioned but 28.3.3.1
> "Operations that invalidate Cached Mappings" does mention that
> the instruction may invalidate mappings associated with other
> EP4TAs (even in single context).
Yes, "may". So we are implementing undefined behavior in order to please
a broken hypervisor that relies on it? Then please state this in the
patch and probably also inform Xen about their issue.
>
> Note that I based this on what we currently do for context invalidation -
> static inline void ept_sync_context(u64 eptp)
> {
> if (enable_ept) {
> if (cpu_has_vmx_invept_context())
> __invept(VMX_EPT_EXTENT_CONTEXT, eptp, 0);
> else
> ept_sync_global();
> }
> }
Don't get your point. This test is about testing for the CPU support
context invalidating, then falling back to global invalidation if there
is no support.
Jan
>
> Seemed easier and cleaner than having a cached eptp after vmcs12 is
> long gone :)
>
> If you prefer, I can modify the commit message to reflect this.
>
>> Jan
>>
>>>
>>> Signed-off-by: Bandan Das <bsd@xxxxxxxxxx>
>>> ---
>>> arch/x86/kvm/vmx.c | 5 +++--
>>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>>> index c707389..b407b3a 100644
>>> --- a/arch/x86/kvm/vmx.c
>>> +++ b/arch/x86/kvm/vmx.c
>>> @@ -6435,8 +6435,9 @@ static int handle_invept(struct kvm_vcpu *vcpu)
>>>
>>> switch (type) {
>>> case VMX_EPT_EXTENT_CONTEXT:
>>> - if ((operand.eptp & eptp_mask) !=
>>> - (nested_ept_get_cr3(vcpu) & eptp_mask))
>>> + if (get_vmcs12(vcpu) &&
>>> + ((operand.eptp & eptp_mask) != (nested_ept_get_cr3(vcpu) &
>>> + eptp_mask)))
>>> break;
>>> case VMX_EPT_EXTENT_GLOBAL:
>>> kvm_mmu_sync_roots(vcpu);
>>>
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