linux-kernel - Re: [PATCH Part2 RFC v4 04/40] x86/sev: Add the host SEV-SNP initialization support

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Message-ID: <YpijNgA9ZJFOwF8k@kernel.org>
Date:   Thu, 2 Jun 2022 14:47:02 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@....fi>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     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>,
        Borislav Petkov <bp@...en8.de>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>, tony.luck@...el.com,
        npmccallum@...hat.com, brijesh.ksingh@...il.com
Subject: Re: [PATCH Part2 RFC v4 04/40] x86/sev: Add the host SEV-SNP
 initialization support

On Wed, Jul 07, 2021 at 01:35:40PM -0500, Brijesh Singh wrote:
> The memory integrity guarantees of SEV-SNP are enforced through a new
> structure called the Reverse Map Table (RMP). The RMP is a single data
> structure shared across the system that contains one entry for every 4K
> page of DRAM that may be used by SEV-SNP VMs. The goal of RMP is to
> track the owner of each page of memory. Pages of memory can be owned by
> the hypervisor, owned by a specific VM or owned by the AMD-SP. See APM2
> section 15.36.3 for more detail on RMP.
> 
> The RMP table is used to enforce access control to memory. The table itself
> is not directly writable by the software. New CPU instructions (RMPUPDATE,
> PVALIDATE, RMPADJUST) are used to manipulate the RMP entries.

What's the point of throwing out a set of opcodes, if there's
no explanation what they do?

BR, Jarkko