linux-kernel - Re: [RFC Part1 PATCH 06/13] x86/compressed: rescinds and validate the memory used for the GHCB

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Message-ID: <20210407112555.GB25319@zn.tnic>
Date:   Wed, 7 Apr 2021 13:25:55 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     Brijesh Singh <brijesh.singh@....com>,
        linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org,
        ak@...ux.intel.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        "H. Peter Anvin" <hpa@...or.com>, Tony Luck <tony.luck@...el.com>,
        Dave Hansen <dave.hansen@...el.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        David Rientjes <rientjes@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC Part1 PATCH 06/13] x86/compressed: rescinds and validate
 the memory used for the GHCB

On Tue, Apr 06, 2021 at 02:42:43PM -0500, Tom Lendacky wrote:
> The GHCB spec only defines the "0" reason code set. We could provide Linux
> it's own reason code set with some more specific reason codes for
> failures, if that is needed.

Why Linux only?

Don't we want to have a generalized set of error codes which say what
has happened so that people can debug?

Let's take the above case Brijesh explains: guest tries a page state
change, HV cannot manage for whatever reason and guest terminates with a
"general request".

Wouldn't you want to at least have a *hint* as to why the guest
terminated instead of just "guest terminated"?

I.e., none of those:

https://duckduckgo.com/?q=dumb+error+messages&iax=images&ia=images

:-)

-- 
Regards/Gruss,
    Boris.

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