linux-kernel - Re: [PATCH Part2 v5 00/45] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support

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Message-ID: <YZ0KgymKvLC2HcIk@google.com>
Date:   Tue, 23 Nov 2021 15:36:35 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Peter Gonda <pgonda@...gle.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...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>,
        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 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>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>, tony.luck@...el.com,
        marcorr@...gle.com, sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH Part2 v5 00/45] Add AMD Secure Nested Paging (SEV-SNP)
 Hypervisor Support

On Tue, Nov 23, 2021, Borislav Petkov wrote:
> On Mon, Nov 22, 2021 at 02:51:35PM -0800, Dave Hansen wrote:
> > By "supporting", do you mean doing something functional?  I don't really
> > care if ptrace() to guest private memory returns -EINVAL or whatever.
> > The most important thing is not crashing the host.
> > 
> > Also, as Sean mentioned, this isn't really about ptrace() itself.  It's
> > really about ensuring that no kernel or devices accesses to guest
> > private memory can induce bad behavior.
> 
> I keep repeating this suggestion of mine that we should treat
> guest-private pages as hw-poisoned pages which have experienced a
> uncorrectable error in the past.
> 
> mm already knows how to stay away from those.

Kirill posted a few RFCs that did exactly that.  It's definitely a viable approach,
but it's a bit of a dead end, e.g. doesn't help solve page migration, is limited to
struct page, doesn't capture which KVM guest owns the memory, etc...

https://lore.kernel.org/kvm/20210416154106.23721-1-kirill.shutemov@linux.intel.com/