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From: Santosh Shukla <santosh.shukla@amd.com>
To: Maxim Levitsky <mlevitsk@redhat.com>,
	pbonzini@redhat.com, seanjc@google.com, jmattson@google.com
Cc: kvm@vger.kernel.org, joro@8bytes.org,
	linux-kernel@vger.kernel.org, mail@maciej.szmigiero.name,
	thomas.lendacky@amd.com, vkuznets@redhat.com,
	santosh.shukla@amd.com
Subject: Re: [PATCHv5 0/8] Virtual NMI feature
Date: Wed, 16 Nov 2022 11:10:31 +0530	[thread overview]
Message-ID: <fc8813c6-0091-8571-d934-e33d7d56123d@amd.com> (raw)
In-Reply-To: <869d05b2ce0437efae1cf505cf4028ceb4920ce2.camel@redhat.com>

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@amd.com/

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
> 


  reply	other threads:[~2022-11-16  5:41 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-27  8:38 [PATCHv5 0/8] Virtual NMI feature Santosh Shukla
2022-10-27  8:38 ` [PATCHv5 1/8] x86/cpu: Add CPUID feature bit for VNMI Santosh Shukla
2022-10-27  8:38 ` [PATCHv5 2/8] KVM: SVM: Add VNMI bit definition Santosh Shukla
2022-10-27  8:38 ` [PATCHv5 3/8] KVM: SVM: Add VNMI support in get/set_nmi_mask Santosh Shukla
2022-10-27  8:38 ` [PATCHv5 4/8] KVM: SVM: Report NMI not allowed when Guest busy handling VNMI Santosh Shukla
2022-10-27  8:38 ` [PATCHv5 5/8] KVM: SVM: Add VNMI support in inject_nmi Santosh Shukla
2022-10-27  8:38 ` [PATCHv5 6/8] KVM: nSVM: implement nested VNMI Santosh Shukla
2022-10-27  8:38 ` [PATCHv5 7/8] KVM: nSVM: emulate VMEXIT_INVALID case for " Santosh Shukla
2022-10-27  8:38 ` [PATCHv5 8/8] KVM: SVM: Enable VNMI feature Santosh Shukla
2022-11-14  8:02 ` [PATCHv5 0/8] Virtual NMI feature Santosh Shukla
2022-11-14 14:31   ` Maxim Levitsky
2022-11-16  5:40     ` Santosh Shukla [this message]
2022-11-16  9:21       ` Maxim Levitsky
2022-11-16 15:44         ` Santosh Shukla
2022-11-16 15:55           ` Tom Lendacky
2022-11-16 16:59             ` Sean Christopherson

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