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

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Date:   Thu, 14 Oct 2021 17:19:54 -0700
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        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 10/14/21 12:28 AM, Thomas Gleixner wrote:
> 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.


It can be included unconditionally. I will remove it in next version.

>
>> +	/* 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.

I will use a meaningful label instead of 1 or 2. I will fix this in next 
version.

>
>> +       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().


Yes, we want to panic here. I will use panic() in next version.


>
> Thanks,
>
>          tglx

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer