linux-kernel - Re: [PATCH v11 05/20] x86/virt/tdx: Add SEAMCALL infrastructure

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Date:   Tue, 20 Jun 2023 08:15:31 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     David Hildenbrand <david@...hat.com>,
        Kai Huang <kai.huang@...el.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     linux-mm@...ck.org, kirill.shutemov@...ux.intel.com,
        tony.luck@...el.com, peterz@...radead.org, tglx@...utronix.de,
        seanjc@...gle.com, pbonzini@...hat.com, dan.j.williams@...el.com,
        rafael.j.wysocki@...el.com, ying.huang@...el.com,
        reinette.chatre@...el.com, len.brown@...el.com, ak@...ux.intel.com,
        isaku.yamahata@...el.com, chao.gao@...el.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, bagasdotme@...il.com,
        sagis@...gle.com, imammedo@...hat.com
Subject: Re: [PATCH v11 05/20] x86/virt/tdx: Add SEAMCALL infrastructure

On 6/19/23 05:52, David Hildenbrand wrote:
>> +    /*
>> +     * SEAMCALL caused #GP or #UD.  By reaching here %eax contains
>> +     * the trap number.  Convert the trap number to the TDX error
>> +     * code by setting TDX_SW_ERROR to the high 32-bits of %rax.
>> +     *
>> +     * Note cannot OR TDX_SW_ERROR directly to %rax as OR instruction
>> +     * only accepts 32-bit immediate at most.
> 
> Not sure if that comment is really helpful here. It's a common pattern
> for large immediates, no?

It's a question of whether you write the comments for folks that read
x86 assembly all the time or not.

I think the comment is helpful.