linux-kernel - Re: [PATCH v8 05/11] x86/tdx: Add __tdx_module_call() and __tdx

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Message-ID: <YV6/Bg9D67sbq6Ap@zn.tnic>
Date:   Thu, 7 Oct 2021 11:33:58 +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>, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>, Deep Shah <sdeep@...are.com>,
        VMware Inc <pv-drivers@...are.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.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>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 05/11] x86/tdx: Add __tdx_module_call() and
 __tdx_hypercall() helper functions

On Mon, Oct 04, 2021 at 07:51:59PM -0700, Kuppuswamy Sathyanarayanan wrote:
> diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
> index ad3ff5925153..d5fc2904facf 100644
> --- a/arch/x86/kernel/tdx.c
> +++ b/arch/x86/kernel/tdx.c
> @@ -27,6 +27,29 @@ static void __init is_tdx_guest_init(void)
>  	is_tdx_guest = !memcmp("IntelTDX    ", sig, 12);
>  }
>  
> +/*
> + * Wrapper for standard use of __tdx_hypercall with BUG_ON() check
> + * for TDCALL error.
> + */
> +static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14,
> +				 u64 r15, struct tdx_hypercall_output *out)
> +{
> +	struct tdx_hypercall_output outl = {0};

Why do you need to clear this when, if used, it will get completely
overwritten in __tdx_hypercall()?

-- 
Regards/Gruss,
    Boris.

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