linux-kernel - Re: [PATCH v5 08/22] x86/virt/tdx: Shut down TDX module in case of error

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Date:   Mon, 27 Jun 2022 17:03:58 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Kai Huang <kai.huang@...el.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     seanjc@...gle.com, pbonzini@...hat.com, len.brown@...el.com,
        tony.luck@...el.com, rafael.j.wysocki@...el.com,
        reinette.chatre@...el.com, dan.j.williams@...el.com,
        peterz@...radead.org, ak@...ux.intel.com,
        kirill.shutemov@...ux.intel.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com,
        isaku.yamahata@...el.com
Subject: Re: [PATCH v5 08/22] x86/virt/tdx: Shut down TDX module in case of
 error

On 6/27/22 16:59, Kai Huang wrote:
> If so,  in the assembly, I think we can just XOR TDX_SW_ERROR to the %rax and
> return %rax:
> 
> 2:
>         /*
> 	 * SEAMCALL caused #GP or #UD.  By reaching here %eax contains
> 	 * the trap number.  Convert trap number to TDX error code by setting
> 	 * TDX_SW_ERROR to the high 32-bits of %rax.
> 	 */
> 	xorq	$TDX_SW_ERROR, %rax
> 
> How does this look?

I guess it doesn't matter if you know the things being masked together
are padded correctly, but I probably would have done a straight OR, not XOR.

Otherwise, I think that looks OK.  Simplifies the assembly for sure.