linux-kernel - Re: [PATCH v10 05/11] x86/tdx: Add __tdx_module_call() and __tdx

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Message-ID: <87r1co6p5y.ffs@tglx>
Date:   Thu, 14 Oct 2021 09:28:25 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        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>
Cc:     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 v10 05/11] x86/tdx: Add __tdx_module_call() and
 __tdx_hypercall() helper functions

On Fri, Oct 08 2021 at 22:37, Kuppuswamy Sathyanarayanan wrote:
>  
> +#ifdef CONFIG_INTEL_TDX_GUEST
> +#include <asm/tdx.h>
> +#endif

Please get rid of the #ifdef and make sure that tdx.h can be included unconditionally.

> +	/* Restore callee-saved GPRs as mandated by the x86_64 ABI */
> +	pop %r12
> +	pop %r13
> +	pop %r14
> +	pop %r15
> +
> +	jmp 2f
> +1:

ASM supports named labels. 

> +       movq $(-EINVAL), %rax
> +2:
> +       FRAME_END
> +
> +       retq
> +SYM_FUNC_END(__tdx_hypercall)


> +/*
> + * 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;
> +	u64 err;
> +
> +	/* __tdx_hypercall() does not accept NULL output pointer */
> +	if (!out)
> +		out = &outl;
> +
> +	err = __tdx_hypercall(TDX_HYPERCALL_STANDARD, fn, r12, r13, r14,
> +			      r15, out);
> +
> +	/* Non zero return value indicates buggy TDX module, so panic */
> +	BUG_ON(err);

BUG() does not necessarily panic. If you want to panic in then invoke
the function which does that, i.e. panic().

Thanks,

        tglx