On Wed, 2022-11-16 at 11:10 +0530, Santosh Shukla wrote: > Hi Maxim, > > On 11/14/2022 8:01 PM, Maxim Levitsky wrote: > > On Mon, 2022-11-14 at 13:32 +0530, Santosh Shukla wrote: > > > > > > > > > On 10/27/2022 2:08 PM, Santosh Shukla wrote: > > > > VNMI Spec is at [1]. > > > > > > > > Change History: > > > > > > > > v5 (6.1-rc2) > > > > 01,02,06 - Renamed s/X86_FEATURE_V_NMI/X86_FEATURE_AMD_VNMI (Jim Mattson) > > > > > > > > > > Gentle reminder. > > > > > > Thanks, > > > Santosh > > > > > > > I started reviewing it today and I think there are still few issues, > > and the biggest one is that if a NMI arrives while vNMI injection > > is pending, current code just drops such NMI. > > > > We had a discussion about this, like forcing immeditate vm exit > > I believe, We discussed above case in [1] i.e.. HW can handle > the second (/pending)virtual NMI while the guest processing first virtual NMI w/o vmexit. > is it same scenario or different one that you are mentioning? > > [1] https://lore.kernel.org/lkml/1782cdbb-8274-8c3d-fa98-29147f1e5d1e@xxxxxxx/ You misunderstood the issue. Hardware can handle the case when a NMI is in service (that is V_NMI_MASK is set) and another one is injected (V_NMI_PENDING can be set), but it is not possible to handle the case when a NMI is already injected (V_NMI_PENDING set) but and KVM wants to inject another one before the first one went into the service (that is V_NMI_MASK is not set yet). Also same can happen when NMIs are blocked in SMM, since V_NMI_MASK is set despite no NMI in service, we will be able to inject only one NMI by setting the V_NMI_PENDING. I think I was able to solve all these issues and I will today post a modified patch series of yours, which should cover all these cases and have some nice refactoring as well. Best regards, Maxim Levitsky > > Thanks, > Santosh > > > in this case and such but I have a simplier idea: > > > > In this case we can just open the NMI window in the good old way > > by intercepting IRET, STGI, and or RSM (which is intercepted anyway), > > > > and only if we already *just* intercepted IRET, only then just drop > > the new NMI instead of single stepping over it based on reasoning that > > its 3rd NMI (one is almost done the servicing (its IRET is executing), > > one is pending injection, and we want to inject another one. > > > > Does this sound good to you? It won't work for SEV-ES as it looks > > like it doesn't intercept IRET, but it might be a reasonable tradeof > > for SEV-ES guests to accept that we can't inject a NMI if one is > > already pending injection. > > > > Best regards, > > Maxim Levitsky > > >
