linux-kernel - Re: [PATCH 1/2] x86/tdx: Extract GET_INFO call from get_cc

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Date:   Mon, 31 Oct 2022 12:27:19 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Dave Hansen <dave.hansen@...el.com>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        luto@...nel.org, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        dan.j.williams@...el.com, david@...hat.com, hpa@...or.com,
        seanjc@...gle.com, thomas.lendacky@....com,
        elena.reshetova@...el.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] x86/tdx: Extract GET_INFO call from get_cc_mask()

sted-by's would be appreciated.
> One thing that I must bring up is that it seems that there's no way to get
> the panic message to user. I tried to convinced myself that it is qemu
> misconfiguration on my part or some race, but no: it is just too early for
> earlyprintk.
>
> We only get earlyprintk working after parse_early_options() which happens
> well after tdx_early_init().
>
> Moving panic() after earlyprintk working is not good idea as it exposes
> kernel more: by the time we already have full #VE handler.


It should be fine to move since there is no user land at this point (the 
attack requires user land)


>
> We can move it earlier into decompresser which has different earlyprintk
> implementation. Not sure if it worth this. What do you think?

That would make uncompressed kernels unsafe.

-Andi