linux-kernel - Re: [RFC PATCH v2 05/69] KVM: TDX: Add architectural definitions for structures and values

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Message-ID: <1057bbfe-c73e-a182-7696-afc59a4786d8@intel.com>
Date:   Mon, 2 Aug 2021 21:25:44 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Erdem Aktas <erdemaktas@...gle.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, x86 <x86@...nel.org>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        isaku.yamahata@...il.com,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Chao Gao <chao.gao@...el.com>
Subject: Re: [RFC PATCH v2 05/69] KVM: TDX: Add architectural definitions for
 structures and values

On 7/31/2021 9:04 AM, Erdem Aktas wrote:
> On Fri, Jul 2, 2021 at 3:05 PM <isaku.yamahata@...el.com> wrote:
>> +/* Management class fields */
>> +enum tdx_guest_management {
>> +       TD_VCPU_PEND_NMI = 11,
>> +};
>> +
>> +/* @field is any of enum tdx_guest_management */
>> +#define TDVPS_MANAGEMENT(field)        BUILD_TDX_FIELD(32, (field))
> 
> I am a little confused with this. According to the spec, PEND_NMI has
> a field code of 0x200000000000000B
> I can understand that 0x20 is the class code and the PEND_NMI field code is 0xB.
> On the other hand, for the LAST_EXIT_TSC the field code is  0xA00000000000000A.

> Based on your code and the table in the spec, I can see that there is
> an additional mask (1ULL<<63) for readonly fields

No. bit 63 is not for readonly fields, but for non_arch fields.

Please see 18.7.1 General definition

> Is this information correct and is this included in the spec? I tried
> to find it but somehow I do not see it clearly defined.
> 
>> +#define TDX1_NR_TDCX_PAGES             4
>> +#define TDX1_NR_TDVPX_PAGES            5
>> +
>> +#define TDX1_MAX_NR_CPUID_CONFIGS      6
> Why is this just 6? I am looking at the CPUID table in the spec and
> there are already more than 6 CPUID leaves there.

This is the number of CPUID config reported by TDH.SYS.INFO. Current KVM 
only reports 6 leaves.

>> +#define TDX1_MAX_NR_CMRS               32
>> +#define TDX1_MAX_NR_TDMRS              64
>> +#define TDX1_MAX_NR_RSVD_AREAS         16
>> +#define TDX1_PAMT_ENTRY_SIZE           16
>> +#define TDX1_EXTENDMR_CHUNKSIZE                256
> 
> I believe all of the defined variables above need to be enumerated
> with TDH.SYS.INFO.

No. Only TDX1_MAX_NR_TDMRS, TDX1_MAX_NR_RSVD_AREAS and 
TDX1_PAMT_ENTRY_SIZE can be enumerated from TDH.SYS.INFO.

- TDX1_MAX_NR_CMRS is described in 18.6.3 CMR_INFO, which tells

   TDH.SYS.INFO leaf function returns a MAX_CMRS(32) entry array
   of CMR_INFO entries.

- TDX1_EXTENDMR_CHUNKSIZE is describe in 20.2.23 TDH.MR.EXTEND

>> +#define TDX_TDMR_ADDR_ALIGNMENT        512
> Is TDX_TDMR_ADDR_ALIGNMENT used anywhere or is it just for completeness?

It's the leftover during rebase. We will clean it up.

>> +#define TDX_TDMR_INFO_ALIGNMENT        512
> Why do we have alignment of 512, I am assuming to make it cache line
> size aligned for efficiency?

It should be leftover too.

SEAMCALL TDH.SYS.INFO requires each cmr info in CMR_INFO_ARRAY to be 
512B aligned

> 
>> +#define TDX_TDSYSINFO_STRUCT_ALIGNEMNT 1024
> 
> typo: ALIGNEMNT -> ALIGNMENT
> 
> -Erdem
>