linux-kernel - Re: [PATCH Part1 RFC v4 16/36] KVM: SVM: define new SEV_FEATURES field in the VMCB Save State Area

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Date:   Tue, 17 Aug 2021 13:11:35 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     brijesh.singh@....com, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>, tony.luck@...el.com,
        npmccallum@...hat.com, brijesh.ksingh@...il.com
Subject: Re: [PATCH Part1 RFC v4 16/36] KVM: SVM: define new SEV_FEATURES
 field in the VMCB Save State Area



On 8/17/21 12:54 PM, Borislav Petkov wrote:
> On Wed, Jul 07, 2021 at 01:14:46PM -0500, Brijesh Singh wrote:
>> The hypervisor uses the SEV_FEATURES field (offset 3B0h) in the Save State
>> Area to control the SEV-SNP guest features such as SNPActive, vTOM,
>> ReflectVC etc. An SEV-SNP guest can read the SEV_FEATURES fields through
>> the SEV_STATUS MSR.
>>
>> While at it, update the dump_vmcb() to log the VMPL level.
>>
>> See APM2 Table 15-34 and B-4 for more details.
>>
>> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
>> ---
>>   arch/x86/include/asm/svm.h | 15 +++++++++++++--
>>   arch/x86/kvm/svm/svm.c     |  4 ++--
>>   2 files changed, 15 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
>> index 772e60efe243..ff614cdcf628 100644
>> --- a/arch/x86/include/asm/svm.h
>> +++ b/arch/x86/include/asm/svm.h
>> @@ -212,6 +212,15 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
>>   #define SVM_NESTED_CTL_SEV_ENABLE	BIT(1)
>>   #define SVM_NESTED_CTL_SEV_ES_ENABLE	BIT(2)
>>   
>> +#define SVM_SEV_FEATURES_SNP_ACTIVE		BIT(0)
>> +#define SVM_SEV_FEATURES_VTOM			BIT(1)
>> +#define SVM_SEV_FEATURES_REFLECT_VC		BIT(2)
>> +#define SVM_SEV_FEATURES_RESTRICTED_INJECTION	BIT(3)
>> +#define SVM_SEV_FEATURES_ALTERNATE_INJECTION	BIT(4)
>> +#define SVM_SEV_FEATURES_DEBUG_SWAP		BIT(5)
>> +#define SVM_SEV_FEATURES_PREVENT_HOST_IBS	BIT(6)
>> +#define SVM_SEV_FEATURES_BTB_ISOLATION		BIT(7)
> 
> Only some of those get used and only later. Please introduce only those
> with the patch that adds usage.
> 

Okay.

> Also,
> 
> s/SVM_SEV_FEATURES_/SVM_SEV_FEAT_/g
> 

I can do that.

> at least.
> 
> And by the way, why is this patch and the next 3 part of the guest set?
> They look like they belong into the hypervisor set.
> 

This is needed by the AP creation, in SNP the AP creation need to 
populate the VMSA page and thus need to use some of macros and fields  etc.