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Date:   Wed, 28 Jun 2023 23:16:41 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Kai Huang <kai.huang@intel.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-mm@kvack.org, x86@kernel.org, dave.hansen@intel.com,
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        ying.huang@intel.com, chao.gao@intel.com,
        sathyanarayanan.kuppuswamy@linux.intel.com, nik.borisov@suse.com,
        bagasdotme@gmail.com, sagis@google.com, imammedo@redhat.com
Subject: Re: [PATCH v12 20/22] x86/virt/tdx: Allow SEAMCALL to handle #UD and
 #GP
Message-ID: <20230628211641.GT38236@hirez.programming.kicks-ass.net>
References: <cover.1687784645.git.kai.huang@intel.com>
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 <20230628152900.GI2438817@hirez.programming.kicks-ass.net>
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 <20230628211132.GS38236@hirez.programming.kicks-ass.net>
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On Wed, Jun 28, 2023 at 11:11:32PM +0200, Peter Zijlstra wrote:
> --- a/arch/x86/virt/vmx/tdx/tdxcall.S
> +++ b/arch/x86/virt/vmx/tdx/tdxcall.S
> @@ -17,37 +17,44 @@
>   *            TDX module and hypercalls to the VMM.
>   * SEAMCALL - used by TDX hosts to make requests to the
>   *            TDX module.
> + *
> + *-------------------------------------------------------------------------
> + * TDCALL/SEAMCALL ABI:
> + *-------------------------------------------------------------------------
> + * Input Registers:
> + *
> + * RAX                 - TDCALL Leaf number.
> + * RCX,RDX,R8-R9       - TDCALL Leaf specific input registers.
> + *
> + * Output Registers:
> + *
> + * RAX                 - TDCALL instruction error code.
> + * RCX,RDX,R8-R11      - TDCALL Leaf specific output registers.
> + *
> + *-------------------------------------------------------------------------
> + *
> + * __tdx_module_call() function ABI:
> + *
> + * @fn   (RDI)         - TDCALL Leaf ID,    moved to RAX
> + * @regs (RSI)         - struct tdx_regs pointer
> + *
> + * Return status of TDCALL via RAX.
>   */
> +.macro TDX_MODULE_CALL host:req ret:req
> +	FRAME_BEGIN
>  
> +	mov	%rdi, %rax
> +	mov	$TDX_SEAMCALL_VMFAILINVALID, %rdi
>  
> +	mov	TDX_MODULE_rcx(%rsi), %rcx
> +	mov	TDX_MODULE_rdx(%rsi), %rdx
> +	mov	TDX_MODULE_r8(%rsi),  %r8
> +	mov	TDX_MODULE_r9(%rsi),  %r9
> +//	mov	TDX_MODULE_r10(%rsi), %r10
> +//	mov	TDX_MODULE_r11(%rsi), %r11
>  
> +.if \host
> +1:	seamcall
>  	/*
>  	 * SEAMCALL instruction is essentially a VMExit from VMX root
>  	 * mode to SEAM VMX root mode.  VMfailInvalid (CF=1) indicates
	...
>  	 * This value will never be used as actual SEAMCALL error code as
>  	 * it is from the Reserved status code class.
>  	 */
> +	cmovc	%rdi, %rax
>  2:
> +.else
>  	tdcall
> +.endif
>  
> +.if \ret
> +	movq %rcx, TDX_MODULE_rcx(%rsi)
> +	movq %rdx, TDX_MODULE_rdx(%rsi)
> +	movq %r8,  TDX_MODULE_r8(%rsi)
> +	movq %r9,  TDX_MODULE_r9(%rsi)
> +	movq %r10, TDX_MODULE_r10(%rsi)
> +	movq %r11, TDX_MODULE_r11(%rsi)
> +.endif
> +
> +	FRAME_END
> +	RET
> +
> +.if \host
> +3:
> +	mov	$TDX_SW_ERROR, %rdi
> +	or	%rdi, %rax
> +	jmp 2b
>  
> +	_ASM_EXTABLE_FAULT(1b, 3b)
> +.endif
>  .endm

Isn't that much simpler?