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From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>,
	Ashish Kalra <Ashish.Kalra@amd.com>
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
	joro@8bytes.org, bp@suse.de, thomas.lendacky@amd.com,
	x86@kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, srutherford@google.com,
	venu.busireddy@oracle.com, brijesh.singh@amd.com
Subject: Re: [PATCH v13 10/12] KVM: x86: Introduce new KVM_FEATURE_SEV_LIVE_MIGRATION feature & Custom MSR.
Date: Tue, 20 Apr 2021 12:49:41 +0200
Message-ID: <988e38b4-2f69-ff66-eac9-e1714c049867@redhat.com> (raw)
In-Reply-To: <YH4M5guOafToCWd7@google.com>

On 20/04/21 01:06, Sean Christopherson wrote:
>> diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
>> index 950afebfba88..f6bfa138874f 100644
>> --- a/arch/x86/include/uapi/asm/kvm_para.h
>> +++ b/arch/x86/include/uapi/asm/kvm_para.h
>> @@ -33,6 +33,7 @@
>>   #define KVM_FEATURE_PV_SCHED_YIELD	13
>>   #define KVM_FEATURE_ASYNC_PF_INT	14
>>   #define KVM_FEATURE_MSI_EXT_DEST_ID	15
>> +#define KVM_FEATURE_SEV_LIVE_MIGRATION	16
>>   
>>   #define KVM_HINTS_REALTIME      0
>>   
>> @@ -54,6 +55,7 @@
>>   #define MSR_KVM_POLL_CONTROL	0x4b564d05
>>   #define MSR_KVM_ASYNC_PF_INT	0x4b564d06
>>   #define MSR_KVM_ASYNC_PF_ACK	0x4b564d07
>> +#define MSR_KVM_SEV_LIVE_MIGRATION	0x4b564d08
>>   
>>   struct kvm_steal_time {
>>   	__u64 steal;
>> @@ -136,4 +138,6 @@ struct kvm_vcpu_pv_apf_data {
>>   #define KVM_PV_EOI_ENABLED KVM_PV_EOI_MASK
>>   #define KVM_PV_EOI_DISABLED 0x0
>>   
>> +#define KVM_SEV_LIVE_MIGRATION_ENABLED BIT_ULL(0)
> 
> Even though the intent is to "force" userspace to intercept the MSR, I think KVM
> should at least emulate the legal bits as a nop.  Deferring completely to
> userspace is rather bizarre as there's not really anything to justify KVM
> getting involved.  It would also force userspace to filter the MSR just to
> support the hypercall.

I think this is the intention, the hypercall by itself cannot do much if
you cannot tell userspace that it's up-to-date.

On the other hand it is kind of wrong that KVM_GET_SUPPORTED_CPUID
returns the feature, but the MSR is not supported.

> Somewhat of a nit, but I think we should do something like s/ENABLED/READY,

Agreed.  I'll send a patch that puts everything together.

Paolo


  reply index

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-15 15:52 [PATCH v13 00/12] Add AMD SEV guest live migration support Ashish Kalra
2021-04-15 15:53 ` [PATCH v13 01/12] KVM: SVM: Add KVM_SEV SEND_START command Ashish Kalra
2021-04-20  8:50   ` Paolo Bonzini
2021-04-15 15:53 ` [PATCH v13 02/12] KVM: SVM: Add KVM_SEND_UPDATE_DATA command Ashish Kalra
2021-04-15 15:54 ` [PATCH v13 03/12] KVM: SVM: Add KVM_SEV_SEND_FINISH command Ashish Kalra
2021-04-15 15:54 ` [PATCH v13 04/12] KVM: SVM: Add support for KVM_SEV_RECEIVE_START command Ashish Kalra
2021-04-20  8:38   ` Paolo Bonzini
2021-04-20  9:18     ` Paolo Bonzini
2021-04-15 15:55 ` [PATCH v13 05/12] KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command Ashish Kalra
2021-04-20  8:40   ` Paolo Bonzini
2021-04-20  8:43     ` Paolo Bonzini
2021-04-15 15:55 ` [PATCH v13 06/12] KVM: SVM: Add KVM_SEV_RECEIVE_FINISH command Ashish Kalra
2021-04-15 15:56 ` [PATCH v13 07/12] KVM: x86: Add AMD SEV specific Hypercall3 Ashish Kalra
2021-04-15 15:57 ` [PATCH v13 08/12] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall Ashish Kalra
2021-04-20 11:10   ` Paolo Bonzini
2021-04-20 17:24     ` Sean Christopherson
2021-04-15 15:57 ` [PATCH v13 09/12] mm: x86: Invoke hypercall when page encryption status is changed Ashish Kalra
2021-04-20  9:39   ` Paolo Bonzini
2021-04-21 10:05   ` Borislav Petkov
2021-04-21 12:00     ` Paolo Bonzini
2021-04-21 14:09       ` Borislav Petkov
2021-04-21 12:12     ` Ashish Kalra
2021-04-21 13:50       ` Brijesh Singh
2021-04-21 13:52       ` Borislav Petkov
2021-04-15 15:58 ` [PATCH v13 10/12] KVM: x86: Introduce new KVM_FEATURE_SEV_LIVE_MIGRATION feature & Custom MSR Ashish Kalra
2021-04-19 23:06   ` Sean Christopherson
2021-04-20 10:49     ` Paolo Bonzini [this message]
2021-04-20  9:47   ` Paolo Bonzini
2021-04-15 15:58 ` [PATCH v13 11/12] EFI: Introduce the new AMD Memory Encryption GUID Ashish Kalra
2021-04-15 16:01 ` [PATCH v13 12/12] x86/kvm: Add guest support for detecting and enabling SEV Live Migration feature Ashish Kalra
2021-04-20 10:52   ` Paolo Bonzini
2021-04-21 14:44   ` Borislav Petkov
2021-04-21 15:22     ` Ashish Kalra
2021-04-21 15:32       ` Borislav Petkov
2021-04-21 15:38     ` Paolo Bonzini
2021-04-21 18:48       ` Ashish Kalra
2021-04-21 19:19         ` Ashish Kalra
2021-04-16 21:43 ` [PATCH v13 00/12] Add AMD SEV guest live migration support Steve Rutherford
2021-04-19 14:40   ` Ashish Kalra
2021-04-20 11:11 ` Paolo Bonzini
2021-04-20 18:51   ` Borislav Petkov
2021-04-20 19:08     ` Paolo Bonzini
2021-04-20 20:28       ` Borislav Petkov

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