diff mbox series

target/i386: kvm: Fix when nested state is needed for migration

Message ID 20190624230514.53326-1-liran.alon@oracle.com (mailing list archive)
State New, archived
Headers show
Series target/i386: kvm: Fix when nested state is needed for migration | expand

Commit Message

Liran Alon June 24, 2019, 11:05 p.m. UTC 
When vCPU is in VMX operation and enters SMM mode,
it temporarily exits VMX operation but KVM maintained nested-state
still stores the VMXON region physical address, i.e. even when the
vCPU is in SMM mode then (nested_state->hdr.vmx.vmxon_pa != -1ull).

Therefore, there is no need to explicitly check for
KVM_STATE_NESTED_SMM_VMXON to determine if it is necessary
to save nested-state as part of migration stream.

In addition, destination must enable eVMCS if it is enabled on
source as specified by the KVM_STATE_NESTED_EVMCS flag, even if
the VMXON region is not set. Thus, change the code to require saving
nested-state as part of migration stream in case it is set.

Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
Signed-off-by: Liran Alon <liran.alon@oracle.com>
---
 target/i386/machine.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Paolo Bonzini July 2, 2019, 4:39 p.m. UTC | #1 
On 25/06/19 01:05, Liran Alon wrote:
> When vCPU is in VMX operation and enters SMM mode,
> it temporarily exits VMX operation but KVM maintained nested-state
> still stores the VMXON region physical address, i.e. even when the
> vCPU is in SMM mode then (nested_state->hdr.vmx.vmxon_pa != -1ull).
> 
> Therefore, there is no need to explicitly check for
> KVM_STATE_NESTED_SMM_VMXON to determine if it is necessary
> to save nested-state as part of migration stream.
> 
> In addition, destination must enable eVMCS if it is enabled on
> source as specified by the KVM_STATE_NESTED_EVMCS flag, even if
> the VMXON region is not set. Thus, change the code to require saving
> nested-state as part of migration stream in case it is set.
> 
> Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
> Signed-off-by: Liran Alon <liran.alon@oracle.com>
> ---
>  target/i386/machine.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/target/i386/machine.c b/target/i386/machine.c
> index 851b249d1a39..e7d72faf9e24 100644
> --- a/target/i386/machine.c
> +++ b/target/i386/machine.c
> @@ -999,7 +999,7 @@ static bool vmx_nested_state_needed(void *opaque)
>  
>      return ((nested_state->format == KVM_STATE_NESTED_FORMAT_VMX) &&
>              ((nested_state->hdr.vmx.vmxon_pa != -1ull) ||
> -             (nested_state->hdr.vmx.smm.flags & KVM_STATE_NESTED_SMM_VMXON)));
> +             (nested_state->flags & KVM_STATE_NESTED_EVMCS)));
>  }
>  
>  static const VMStateDescription vmstate_vmx_nested_state = {
> 

Queued, thanks.

Paolo
Liran Alon July 4, 2019, 2:31 p.m. UTC | #2 
> On 2 Jul 2019, at 19:39, Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
> On 25/06/19 01:05, Liran Alon wrote:
>> When vCPU is in VMX operation and enters SMM mode,
>> it temporarily exits VMX operation but KVM maintained nested-state
>> still stores the VMXON region physical address, i.e. even when the
>> vCPU is in SMM mode then (nested_state->hdr.vmx.vmxon_pa != -1ull).
>> 
>> Therefore, there is no need to explicitly check for
>> KVM_STATE_NESTED_SMM_VMXON to determine if it is necessary
>> to save nested-state as part of migration stream.
>> 
>> In addition, destination must enable eVMCS if it is enabled on
>> source as specified by the KVM_STATE_NESTED_EVMCS flag, even if
>> the VMXON region is not set. Thus, change the code to require saving
>> nested-state as part of migration stream in case it is set.
>> 
>> Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
>> Signed-off-by: Liran Alon <liran.alon@oracle.com>
>> ---
>> target/i386/machine.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/target/i386/machine.c b/target/i386/machine.c
>> index 851b249d1a39..e7d72faf9e24 100644
>> --- a/target/i386/machine.c
>> +++ b/target/i386/machine.c
>> @@ -999,7 +999,7 @@ static bool vmx_nested_state_needed(void *opaque)
>> 
>>     return ((nested_state->format == KVM_STATE_NESTED_FORMAT_VMX) &&
>>             ((nested_state->hdr.vmx.vmxon_pa != -1ull) ||
>> -             (nested_state->hdr.vmx.smm.flags & KVM_STATE_NESTED_SMM_VMXON)));
>> +             (nested_state->flags & KVM_STATE_NESTED_EVMCS)));
>> }
>> 
>> static const VMStateDescription vmstate_vmx_nested_state = {
>> 
> 
> Queued, thanks.
> 
> Paolo

Actually Paolo after I have created KVM patch
("KVM: nVMX: Change KVM_STATE_NESTED_EVMCS to signal vmcs12 is copied from eVMCS”)
I think I realised that KVM_STATE_NESTED_EVMCS is actually not a requirement for nested-state to be sent.
I suggest to replace this commit with another one that just change vmx_nested_state_needed() to return true
In case format is FORMAT_VMX and vmxon_pa != -1ull and that’s it.

As anyway, QEMU provisioned on destination side is going to enable the relevant eVMCS capability.
I’m going to send another series that refines QEMU nested-migration a bit more so I will do it along the way.
But I think this patch should be un-queued. Sorry for realizing this later but at least it’s before it was merged to master :)

-Liran
Paolo Bonzini July 4, 2019, 3:29 p.m. UTC | #3 
On 04/07/19 16:31, Liran Alon wrote:
> 
> 
>> On 2 Jul 2019, at 19:39, Paolo Bonzini <pbonzini@redhat.com> wrote:
>>
>> On 25/06/19 01:05, Liran Alon wrote:
>>> When vCPU is in VMX operation and enters SMM mode,
>>> it temporarily exits VMX operation but KVM maintained nested-state
>>> still stores the VMXON region physical address, i.e. even when the
>>> vCPU is in SMM mode then (nested_state->hdr.vmx.vmxon_pa != -1ull).
>>>
>>> Therefore, there is no need to explicitly check for
>>> KVM_STATE_NESTED_SMM_VMXON to determine if it is necessary
>>> to save nested-state as part of migration stream.
>>>
>>> In addition, destination must enable eVMCS if it is enabled on
>>> source as specified by the KVM_STATE_NESTED_EVMCS flag, even if
>>> the VMXON region is not set. Thus, change the code to require saving
>>> nested-state as part of migration stream in case it is set.
>>>
>>> Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
>>> Signed-off-by: Liran Alon <liran.alon@oracle.com>
>>> ---
>>> target/i386/machine.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/target/i386/machine.c b/target/i386/machine.c
>>> index 851b249d1a39..e7d72faf9e24 100644
>>> --- a/target/i386/machine.c
>>> +++ b/target/i386/machine.c
>>> @@ -999,7 +999,7 @@ static bool vmx_nested_state_needed(void *opaque)
>>>
>>>     return ((nested_state->format == KVM_STATE_NESTED_FORMAT_VMX) &&
>>>             ((nested_state->hdr.vmx.vmxon_pa != -1ull) ||
>>> -             (nested_state->hdr.vmx.smm.flags & KVM_STATE_NESTED_SMM_VMXON)));
>>> +             (nested_state->flags & KVM_STATE_NESTED_EVMCS)));
>>> }
>>>
>>> static const VMStateDescription vmstate_vmx_nested_state = {
>>>
>>
>> Queued, thanks.
>>
>> Paolo
> 
> Actually Paolo after I have created KVM patch
> ("KVM: nVMX: Change KVM_STATE_NESTED_EVMCS to signal vmcs12 is copied from eVMCS”)
> I think I realised that KVM_STATE_NESTED_EVMCS is actually not a requirement for nested-state to be sent.
> I suggest to replace this commit with another one that just change vmx_nested_state_needed() to return true
> In case format is FORMAT_VMX and vmxon_pa != -1ull and that’s it.
> 
> As anyway, QEMU provisioned on destination side is going to enable the relevant eVMCS capability.
> I’m going to send another series that refines QEMU nested-migration a bit more so I will do it along the way.
> But I think this patch should be un-queued. Sorry for realizing this later but at least it’s before it was merged to master :)

Replaced with

diff --git a/target/i386/machine.c b/target/i386/machine.c
index 851b249d1a..704ba6de46 100644
--- a/target/i386/machine.c
+++ b/target/i386/machine.c
@@ -997,9 +997,8 @@ static bool vmx_nested_state_needed(void *opaque)
 {
     struct kvm_nested_state *nested_state = opaque;
 
-    return ((nested_state->format == KVM_STATE_NESTED_FORMAT_VMX) &&
-            ((nested_state->hdr.vmx.vmxon_pa != -1ull) ||
-             (nested_state->hdr.vmx.smm.flags & KVM_STATE_NESTED_SMM_VMXON)));
+    return (nested_state->format == KVM_STATE_NESTED_FORMAT_VMX &&
+            nested_state->hdr.vmx.vmxon_pa != -1ull);
 }
 
 static const VMStateDescription vmstate_vmx_nested_state = {

and dropped the last paragraph of the commit message.

Paolo
Liran Alon July 4, 2019, 3:34 p.m. UTC | #4 
> On 4 Jul 2019, at 18:29, Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
> On 04/07/19 16:31, Liran Alon wrote:
>> 
>> 
>>> On 2 Jul 2019, at 19:39, Paolo Bonzini <pbonzini@redhat.com> wrote:
>>> 
>>> On 25/06/19 01:05, Liran Alon wrote:
>>>> When vCPU is in VMX operation and enters SMM mode,
>>>> it temporarily exits VMX operation but KVM maintained nested-state
>>>> still stores the VMXON region physical address, i.e. even when the
>>>> vCPU is in SMM mode then (nested_state->hdr.vmx.vmxon_pa != -1ull).
>>>> 
>>>> Therefore, there is no need to explicitly check for
>>>> KVM_STATE_NESTED_SMM_VMXON to determine if it is necessary
>>>> to save nested-state as part of migration stream.
>>>> 
>>>> In addition, destination must enable eVMCS if it is enabled on
>>>> source as specified by the KVM_STATE_NESTED_EVMCS flag, even if
>>>> the VMXON region is not set. Thus, change the code to require saving
>>>> nested-state as part of migration stream in case it is set.
>>>> 
>>>> Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
>>>> Signed-off-by: Liran Alon <liran.alon@oracle.com>
>>>> ---
>>>> target/i386/machine.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>> 
>>>> diff --git a/target/i386/machine.c b/target/i386/machine.c
>>>> index 851b249d1a39..e7d72faf9e24 100644
>>>> --- a/target/i386/machine.c
>>>> +++ b/target/i386/machine.c
>>>> @@ -999,7 +999,7 @@ static bool vmx_nested_state_needed(void *opaque)
>>>> 
>>>>    return ((nested_state->format == KVM_STATE_NESTED_FORMAT_VMX) &&
>>>>            ((nested_state->hdr.vmx.vmxon_pa != -1ull) ||
>>>> -             (nested_state->hdr.vmx.smm.flags & KVM_STATE_NESTED_SMM_VMXON)));
>>>> +             (nested_state->flags & KVM_STATE_NESTED_EVMCS)));
>>>> }
>>>> 
>>>> static const VMStateDescription vmstate_vmx_nested_state = {
>>>> 
>>> 
>>> Queued, thanks.
>>> 
>>> Paolo
>> 
>> Actually Paolo after I have created KVM patch
>> ("KVM: nVMX: Change KVM_STATE_NESTED_EVMCS to signal vmcs12 is copied from eVMCS”)
>> I think I realised that KVM_STATE_NESTED_EVMCS is actually not a requirement for nested-state to be sent.
>> I suggest to replace this commit with another one that just change vmx_nested_state_needed() to return true
>> In case format is FORMAT_VMX and vmxon_pa != -1ull and that’s it.
>> 
>> As anyway, QEMU provisioned on destination side is going to enable the relevant eVMCS capability.
>> I’m going to send another series that refines QEMU nested-migration a bit more so I will do it along the way.
>> But I think this patch should be un-queued. Sorry for realizing this later but at least it’s before it was merged to master :)
> 
> Replaced with
> 
> diff --git a/target/i386/machine.c b/target/i386/machine.c
> index 851b249d1a..704ba6de46 100644
> --- a/target/i386/machine.c
> +++ b/target/i386/machine.c
> @@ -997,9 +997,8 @@ static bool vmx_nested_state_needed(void *opaque)
> {
>     struct kvm_nested_state *nested_state = opaque;
> 
> -    return ((nested_state->format == KVM_STATE_NESTED_FORMAT_VMX) &&
> -            ((nested_state->hdr.vmx.vmxon_pa != -1ull) ||
> -             (nested_state->hdr.vmx.smm.flags & KVM_STATE_NESTED_SMM_VMXON)));
> +    return (nested_state->format == KVM_STATE_NESTED_FORMAT_VMX &&
> +            nested_state->hdr.vmx.vmxon_pa != -1ull);
> }
> 
> static const VMStateDescription vmstate_vmx_nested_state = {
> 
> and dropped the last paragraph of the commit message.
> 
> Paolo
> 

Yep that’s what I wanted to do.
Thanks. I have some more patches pending anyway but unrelated to this. This now seems good to me.

-Liran
diff mbox series

Patch

diff --git a/target/i386/machine.c b/target/i386/machine.c
index 851b249d1a39..e7d72faf9e24 100644
--- a/target/i386/machine.c
+++ b/target/i386/machine.c
@@ -999,7 +999,7 @@  static bool vmx_nested_state_needed(void *opaque)
 
     return ((nested_state->format == KVM_STATE_NESTED_FORMAT_VMX) &&
             ((nested_state->hdr.vmx.vmxon_pa != -1ull) ||
-             (nested_state->hdr.vmx.smm.flags & KVM_STATE_NESTED_SMM_VMXON)));
+             (nested_state->flags & KVM_STATE_NESTED_EVMCS)));
 }
 
 static const VMStateDescription vmstate_vmx_nested_state = {