linux-kernel - Re: [PATCH 4/9] x86/virt/tdx: Abstract reading multiple global metadata fields as a helper

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Date: Tue, 18 Jun 2024 14:45:37 +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 4/9] x86/virt/tdx: Abstract reading multiple global
 metadata fields as a helper



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.  Future changes will need to read other metadata fields that
> don't make sense to populate to the "struct tdx_tdmr_sysinfo".
> 
> Now the code in get_tdx_tdmr_sysinfo() to read multiple global metadata
> fields is not bound to the 'struct tdx_tdmr_sysinfo', and can support
> reading all metadata element sizes.  Abstract this code as a helper for
> future use.
> 
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> ---
>   arch/x86/virt/vmx/tdx/tdx.c | 27 ++++++++++++++++-----------
>   1 file changed, 16 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index 4392e82a9bcb..c68fbaf4aa15 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -304,6 +304,21 @@ struct field_mapping {
>   	  .offset   = offsetof(_struct, _member),		\
>   	  .size	    = sizeof(typeof(((_struct *)0)->_member)) }
>   
> +static int stbuf_read_sysmd_multi(const struct field_mapping *fields,

Rename it to read_system_metadata_fields i.e just use the plural form of 
the single field function. Whatever you choose to rename the singular 
form, just make this function be the plural. But as a general remark - I 
don't see what value the "stbuf" prefix brings. 'sysmd' is also somewhat 
unintuitive. Any of 
read_metadata_fields/read_sys_metadata_fields/read_system_metadata_fields 
seem better.

> +				  int nr_fields, void *stbuf)
> +{
> +	int i, ret;
> +
> +	for (i = 0; i < nr_fields; i++) {
> +		ret = stbuf_read_sysmd_field(fields[i].field_id, stbuf,
> +				      fields[i].offset, fields[i].size);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
>   #define TD_SYSINFO_MAP_TDMR_INFO(_field_id, _member)	\
>   	TD_SYSINFO_MAP(_field_id, struct tdx_tdmr_sysinfo, _member)
>   

<snip>