Re: [PATCHv3 5/8] KVM: SVM: Add VNMI support in inject_nmi
From: Maciej S. Szmigiero
Date: Thu Aug 25 2022 - 10:16:31 EST
On 25.08.2022 16:05, Shukla, Santosh wrote:
On 8/25/2022 6:15 PM, Maciej S. Szmigiero wrote:
On 25.08.2022 12:56, Shukla, Santosh wrote:
On 8/24/2022 6:26 PM, Maciej S. Szmigiero wrote:
On 24.08.2022 14:13, Shukla, Santosh wrote:
Hi Maciej,
On 8/11/2022 2:54 AM, Maciej S. Szmigiero wrote:
On 10.08.2022 08:12, Santosh Shukla wrote:
Inject the NMI by setting V_NMI in the VMCB interrupt control. processor
will clear V_NMI to acknowledge processing has started and will keep the
V_NMI_MASK set until the processor is done with processing the NMI event.
Signed-off-by: Santosh Shukla <santosh.shukla@xxxxxxx>
---
v3:
- Removed WARN_ON check.
v2:
- Added WARN_ON check for vnmi pending.
- use `get_vnmi_vmcb` to get correct vmcb so to inject vnmi.
arch/x86/kvm/svm/svm.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index e260e8cb0c81..8c4098b8a63e 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3479,7 +3479,14 @@ static void pre_svm_run(struct kvm_vcpu *vcpu)
static void svm_inject_nmi(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);
+ struct vmcb *vmcb = NULL;
+ if (is_vnmi_enabled(svm)) {
I guess this should be "is_vnmi_enabled(svm) && !svm->nmi_l1_to_l2"
since if nmi_l1_to_l2 is true then the NMI to be injected originally
comes from L1's VMCB12 EVENTINJ field.
Not sure if I understood the case fully.. so trying to sketch scenario here -
if nmi_l1_to_l2 is true then event is coming from EVTINJ. .which could
be one of following case -
1) L0 (vnmi enabled) and L1 (vnmi disabled)
As far as I can see in this case:
is_vnmi_enabled() returns whether VMCB02's int_ctl has V_NMI_ENABLE bit set.
For L1 with vnmi disabled case - is_vnmi_enabled()->get_vnmi_vmcb() will return false so the
execution path will opt EVTINJ model for re-injection.
I guess by "get_vnmi_vmcb() will return false" you mean it will return NULL,
since this function returns a pointer, not a bool.
Yes, I meant is_vnmi_enabled() will return false if vnmi param is unset.
I can't see however, how this will happen:
static inline struct vmcb *get_vnmi_vmcb(struct vcpu_svm *svm)
{
if (!vnmi)
return NULL;
^ "vnmi" variable controls whether L0 uses vNMI,
so this variable is true in our case
No.
In L1 case (vnmi disabled) - vnmi param will be false.
Perhaps there was a misunderstanding here - the case here
isn't the code under discussion running as L1, but as L0
where L1 not using vNMI - L1 here can be an old version of KVM,
or Hyper-V, or any other hypervisor.
In this case L0 is re-injecting an EVENTINJ NMI into L2 on
the behalf of L1.
That's when "nmi_l1_to_l2" is true.
Since the code is physically running on L0 (which makes use of vNMI)
it has the "vnmi" param set.
So is_vnmi_enabled() will return true and vNMI will be used
for the re-injection instead of the required EVENTINJ.
In L0 case (vnmi enabled) - vnmi param will be true.
So in L1 case, is_vnmi_enabled() will return false and
in L0 case will return true.
Thanks,
Santosh
Thanks,
Maciej