linux-kernel - Re: [RFC Part2 PATCH 02/30] x86/sev-snp: add RMP entry lookup helpers

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Date:   Thu, 15 Apr 2021 17:18:55 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     brijesh.singh@....com, linux-kernel@...r.kernel.org,
        x86@...nel.org, kvm@...r.kernel.org, linux-crypto@...r.kernel.org,
        ak@...ux.intel.com, herbert@...dor.apana.org.au,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        "H. Peter Anvin" <hpa@...or.com>, Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        David Rientjes <rientjes@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC Part2 PATCH 02/30] x86/sev-snp: add RMP entry lookup helpers


On 4/15/21 2:50 PM, Borislav Petkov wrote:
> On Thu, Apr 15, 2021 at 01:08:09PM -0500, Brijesh Singh wrote:
>> This is from Family 19h Model 01h Rev B01. The processor which
>> introduces the SNP feature. Yes, I have already upload the PPR on the BZ.
>>
>> The PPR is also available at AMD: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.amd.com%2Fen%2Fsupport%2Ftech-docs&amp;data=04%7C01%7Cbrijesh.singh%40amd.com%7Ca20ef8e85fca49875f4b08d90047b837%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637541130354491050%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=MosOIntXEk6ikXpIFd89XkZPb8H6oO25y2mP2l82blU%3D&amp;reserved=0
> Please add the link in the bugzilla to the comments here - this is the
> reason why stuff is being uploaded in the first place, because those
> vendor sites tend to change and those links become stale with time.

Will do.


>
>> I guess I was trying to shorten the name. I am good with struct rmpentry;
> Yes please - typedefs are used only in very specific cases.
>
>> All those magic numbers are documented in the PPR.
> We use defines - not magic numbers. For example
>
> #define RMPTABLE_ENTRIES_OFFSET 0x4000
>
> The 8 is probably
>
> PAGE_SHIFT - RMPENTRY_SHIFT
>
> because you have GPA bits [50:12] and an RMP entry is 16 bytes, i.e., 1 << 4.
>
> With defines it is actually clear what the computation is doing - with
> naked numbers not really.

Sure, I will add macros to make it more readable.