linux-kernel - Re: [PATCHv6 02/15] mm: Add support for unaccepted memory

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Message-ID: <8dfc48f9-80a2-fc3f-4d2a-08abae59548f@amd.com>
Date:   Thu, 19 May 2022 16:33:15 +0200
From:   "Gupta, Pankaj" <pankaj.gupta@....com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Borislav Petkov <bp@...en8.de>, Andy Lutomirski <luto@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>,
        Ard Biesheuvel <ardb@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Varad Gautam <varad.gautam@...e.com>,
        Dario Faggioli <dfaggioli@...e.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Mike Rapoport <rppt@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        x86@...nel.org, linux-mm@...ck.org, linux-coco@...ts.linux.dev,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCHv6 02/15] mm: Add support for unaccepted memory


> On Thu, May 19, 2022 at 12:43:15PM +0200, Gupta, Pankaj wrote:
>> If both Intel TDX and AMD SEV-SNP requires the memory to be accepted before
>> it can be used by the guest. In what other use cases (apart from memory
>> hotplug), the lazy memory acceptance will be useful?
> 
> It is nothing to do with hotplug.
> 
> Any memory has to be accepted before it can be used inside the TDX or
> SEV-SNP guest. It can happen upfront, before kernel gets control (like by
> firmware) or by kernel. The idea is to accept small portion of the memory
> upfront and leave the rest to the kernel. The reason why delaying
> acceptance make sense is boot time. We want the guest to start doing
> useful stuff as fast as possible.

o.k. That answers my question. Thank you!

Best regards,
Pankaj