Re: [PATCH 03/10] x86/tdx: Move FRAME_BEGIN/END to TDX_MODULE_CALL asm macro

From: Isaku Yamahata
Date: Wed Jul 12 2023 - 18:05:58 EST


On Wed, Jul 12, 2023 at 08:55:17PM +1200,
Kai Huang <kai.huang@xxxxxxxxx> wrote:

> Currently, the TDX_MODULE_CALL asm macro and the __tdx_module_call()
> take registers directly as input and a 'struct tdx_module_output' as
> optional output. This is different from the __tdx_hypercall(), which
> simply uses a structure to carry all input/output. There's no point to
> leave __tdx_module_call() complicated as it is.
>
> As a preparation to simplify the __tdx_module_call() to make it look
> like __tdx_hypercall(), move FRAME_BEGIN/END and RET from the
> __tdx_module_call() to the TDX_MODULE_CALL assembly macro. This also
> allows more implementation flexibility of the assembly inside the
> TDX_MODULE_CALL macro, e.g., allowing putting an _ASM_EXTABLE() after
> the main body of the assembly.
>
> This is basically based on Peter's code.
>
> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx>
> ---
> arch/x86/coco/tdx/tdcall.S | 3 ---
> arch/x86/virt/vmx/tdx/tdxcall.S | 5 +++++
> 2 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S
> index 2eca5f43734f..e5d4b7d8ecd4 100644
> --- a/arch/x86/coco/tdx/tdcall.S
> +++ b/arch/x86/coco/tdx/tdcall.S
> @@ -78,10 +78,7 @@
> * Return status of TDCALL via RAX.
> */
> SYM_FUNC_START(__tdx_module_call)
> - FRAME_BEGIN
> TDX_MODULE_CALL host=0
> - FRAME_END
> - RET
> SYM_FUNC_END(__tdx_module_call)
>
> /*
> diff --git a/arch/x86/virt/vmx/tdx/tdxcall.S b/arch/x86/virt/vmx/tdx/tdxcall.S
> index 3524915d8bd9..b5ab919c7fa8 100644
> --- a/arch/x86/virt/vmx/tdx/tdxcall.S
> +++ b/arch/x86/virt/vmx/tdx/tdxcall.S
> @@ -1,5 +1,6 @@
> /* SPDX-License-Identifier: GPL-2.0 */
> #include <asm/asm-offsets.h>
> +#include <asm/frame.h>
> #include <asm/tdx.h>
>
> /*
> @@ -18,6 +19,7 @@
> * TDX module.
> */
> .macro TDX_MODULE_CALL host:req
> + FRAME_BEGIN
> /*
> * R12 will be used as temporary storage for struct tdx_module_output
> * pointer. Since R12-R15 registers are not used by TDCALL/SEAMCALL
> @@ -91,4 +93,7 @@
> .Lno_output_struct:
> /* Restore the state of R12 register */
> pop %r12
> +
> + FRAME_END
> + RET
> .endm
> --
> 2.41.0
>

Reviewed-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
--
Isaku Yamahata <isaku.yamahata@xxxxxxxxx>