linux-kernel - Re: [PATCH v2 2/4] mm: x86: Invoke hypercall when page encryption status is changed

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Date:   Wed, 12 May 2021 18:23:27 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Ashish Kalra <Ashish.Kalra@....com>, pbonzini@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        joro@...tes.org, thomas.lendacky@....com, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        srutherford@...gle.com, venu.busireddy@...cle.com,
        brijesh.singh@....com
Subject: Re: [PATCH v2 2/4] mm: x86: Invoke hypercall when page encryption
 status is changed

On Wed, May 12, 2021 at 03:51:10PM +0000, Sean Christopherson wrote:
>   TL;DR: I think the KVM hypercall should be something like this, so that it can
>   be used for SNP and TDX, and possibly for other purposes, e.g. for paravirt
>   performance enhancements or something.

Ok, good, I was only making sure this is on people's radar but it
actually is more than that. I'll let Tom and Jörg comment on the meat
of the thing - as always, thanks for the detailed explanation.

>From my !virt guy POV, I like the aspect of sharing stuff as much as
possible and it all makes sense to me but what the hell do I know...

>     8. KVM_HC_MAP_GPA_RANGE
>     -----------------------
>     :Architecture: x86
>     :Status: active
>     :Purpose: Request KVM to map a GPA range with the specified attributes.
> 
>     a0: the guest physical address of the start page
>     a1: the number of (4kb) pages (must be contiguous in GPA space)
>     a2: attributes
> 
>   where 'attributes' could be something like:
> 
>     bits  3:0 - preferred page size encoding 0 = 4kb, 1 = 2mb, 2 = 1gb, etc...
>     bit     4 - plaintext = 0, encrypted = 1
>     bits 63:5 - reserved (must be zero)

Yah, nice and simple. I like.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette