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

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Message-ID: <YZKLpiinvKcE896u@work-vm>
Date:   Mon, 15 Nov 2021 16:32:38 +0000
From:   "Dr. David Alan Gilbert" <dgilbert@...hat.com>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...el.com>,
        Peter Gonda <pgonda@...gle.com>,
        Brijesh Singh <brijesh.singh@....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>,
        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

* Joerg Roedel (jroedel@...e.de) wrote:
> On Mon, Nov 15, 2021 at 03:33:03PM +0000, Dr. David Alan Gilbert wrote:
> > How would you debug an unexpected access by the host kernel using a
> > guests kdump?
> 
> The host needs to log the access in some way (trace-event, pr_err) with
> relevant information.

Yeh OK that makes sense if the host-owner could then enable some type of
debugging based on that event for the unfortunate guest owner.

> And with the guest-side kdump you can rule out that it was a guest bug
> which triggered the access. And you learn what the guest was trying to
> do when it triggered the access. This also helps finding the issue on
> the host side (if it is a host-side issue).
> 
> (Guest and host owner need to work together for debugging, of course).

Yeh.

Dave

> Regards,
> 
> -- 
> Jörg Rödel
> jroedel@...e.de
> 
> SUSE Software Solutions Germany GmbH
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-- 
Dr. David Alan Gilbert / dgilbert@...hat.com / Manchester, UK