linux-kernel - Re: [PATCH v2 04/12] x86/x86: Add early_is_tdx

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Date:   Thu, 17 Jun 2021 19:05:00 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Peter H Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 04/12] x86/x86: Add early_is_tdx_guest() interface

On Sat, Jun 12, 2021 at 02:04:45PM -0700, Kuppuswamy Sathyanarayanan wrote:

> Subject: Re: [PATCH v2 04/12] x86/x86: Add early_is_tdx_guest() interface

Subject prefix should be "x86/tdx:" ofc.

> diff --git a/arch/x86/boot/compressed/tdx.c b/arch/x86/boot/compressed/tdx.c
> new file mode 100644
> index 000000000000..ddfa4a6d1939
> --- /dev/null
> +++ b/arch/x86/boot/compressed/tdx.c
> @@ -0,0 +1,28 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * tdx.c - Early boot code for TDX
> + */
> +
> +#include <asm/tdx.h>

Please no kernel proper includes in the decompressor stage - that thing
is an include hell mess and needs cleaning up. Use cpuid_count() from
arch/x86/boot/cpuflags.c by exporting it properly and add the other
defines here instead of using kernel proper facilities.

I know, I know, there is other misuse but it has to stop.

> +static int __ro_after_init tdx_guest = -1;
> +
> +static inline bool native_cpuid_has_tdx_guest(void)

Why is this function prefixed with "native_"?

> +{
> +	u32 eax = TDX_CPUID_LEAF_ID, sig[3] = {0};
> +
> +	if (native_cpuid_eax(0) < TDX_CPUID_LEAF_ID)
> +		return false;
> +
> +	native_cpuid(&eax, &sig[0], &sig[1], &sig[2]);
> +
> +	return !memcmp("IntelTDX    ", sig, 12);
> +}
> +
> +bool early_is_tdx_guest(void)

So I guess this is going to be used somewhere, because I don't see it.
Or is it going away in favor of prot_guest_has(PR_GUEST_TDX) ?

This is the problem with sending new versions of patches as a reply to
the old ones in the patchset: I get confused. Why don't you wait until
the whole thing has been reviewed and then send a new revision which has
all the changes and I can find my way in the context?

And with the amount of changes so far, you should probably send a new
revision of the initial support set now-ish instead of me reviewing this
one 'til the end.

Thx.

-- 
Regards/Gruss,
    Boris.

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