linux-kernel - Re: [PATCH 5/9] x86/virt/tdx: Move field mapping table of getting TDMR info to function local

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Date: Tue, 18 Jun 2024 14:47:51 +0300
From: Nikolay Borisov <nik.borisov@...e.com>
To: Kai Huang <kai.huang@...el.com>, linux-kernel@...r.kernel.org
Cc: x86@...nel.org, dave.hansen@...el.com, dan.j.williams@...el.com,
 kirill.shutemov@...ux.intel.com, rick.p.edgecombe@...el.com,
 peterz@...radead.org, tglx@...utronix.de, bp@...en8.de, mingo@...hat.com,
 hpa@...or.com, seanjc@...gle.com, pbonzini@...hat.com, kvm@...r.kernel.org,
 isaku.yamahata@...el.com, binbin.wu@...ux.intel.com
Subject: Re: [PATCH 5/9] x86/virt/tdx: Move field mapping table of getting
 TDMR info to function local



On 16.06.24 г. 15:01 ч., Kai Huang wrote:
> For now the kernel only reads "TD Memory Region" (TDMR) related global
> metadata fields to a 'struct tdx_tdmr_sysinfo' for initializing the TDX
> module.  The kernel populates the relevant metadata fields into the
> structure using a "field mapping table" of metadata field IDs and the
> structure members.
> 
> Currently the scope of this "field mapping table" is the entire C file.
> Future changes will need to read more global metadata fields that will
> be organized in other structures and use this kind of field mapping
> tables for other structures too.
> 
> Move the field mapping table to the function local to limit its scope so
> that the same name can also be used by other functions.

nit: I think all of this could be condensed simply to :

"The mapping table is only used by foo() so move it there, no functional 
changes". The consideration for future usage seems somewhat moot with 
respect to such a trivial change. In any case:

Reviewed-by: Nikolay Borisov <nik.borisov@...e.com>


> 
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> ---
>   arch/x86/virt/vmx/tdx/tdx.c | 18 +++++++++---------
>   1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index c68fbaf4aa15..fad42014ca37 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -322,17 +322,17 @@ static int stbuf_read_sysmd_multi(const struct field_mapping *fields,
>   #define TD_SYSINFO_MAP_TDMR_INFO(_field_id, _member)	\
>   	TD_SYSINFO_MAP(_field_id, struct tdx_tdmr_sysinfo, _member)
>   
> -/* Map TD_SYSINFO fields into 'struct tdx_tdmr_sysinfo': */
> -static const struct field_mapping fields[] = {
> -	TD_SYSINFO_MAP_TDMR_INFO(MAX_TDMRS,		max_tdmrs),
> -	TD_SYSINFO_MAP_TDMR_INFO(MAX_RESERVED_PER_TDMR, max_reserved_per_tdmr),
> -	TD_SYSINFO_MAP_TDMR_INFO(PAMT_4K_ENTRY_SIZE,    pamt_entry_size[TDX_PS_4K]),
> -	TD_SYSINFO_MAP_TDMR_INFO(PAMT_2M_ENTRY_SIZE,    pamt_entry_size[TDX_PS_2M]),
> -	TD_SYSINFO_MAP_TDMR_INFO(PAMT_1G_ENTRY_SIZE,    pamt_entry_size[TDX_PS_1G]),
> -};
> -
>   static int get_tdx_tdmr_sysinfo(struct tdx_tdmr_sysinfo *tdmr_sysinfo)
>   {
> +	/* Map TD_SYSINFO fields into 'struct tdx_tdmr_sysinfo': */
> +	static const struct field_mapping fields[] = {
> +		TD_SYSINFO_MAP_TDMR_INFO(MAX_TDMRS,		max_tdmrs),
> +		TD_SYSINFO_MAP_TDMR_INFO(MAX_RESERVED_PER_TDMR, max_reserved_per_tdmr),
> +		TD_SYSINFO_MAP_TDMR_INFO(PAMT_4K_ENTRY_SIZE,    pamt_entry_size[TDX_PS_4K]),
> +		TD_SYSINFO_MAP_TDMR_INFO(PAMT_2M_ENTRY_SIZE,    pamt_entry_size[TDX_PS_2M]),
> +		TD_SYSINFO_MAP_TDMR_INFO(PAMT_1G_ENTRY_SIZE,    pamt_entry_size[TDX_PS_1G]),
> +	};
> +
>   	/* Populate 'tdmr_sysinfo' fields using the mapping structure above: */
>   	return stbuf_read_sysmd_multi(fields, ARRAY_SIZE(fields), tdmr_sysinfo);
>   }