linux-kernel - Re: [PATCH v15 09/23] x86/virt/tdx: Get module global metadata for module initialization

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Message-ID: <96b0d0b4-4563-4012-8147-4318b096a435@intel.com>
Date:   Thu, 9 Nov 2023 15:29:05 -0800
From:   Dave Hansen <dave.hansen@...el.com>
To:     Kai Huang <kai.huang@...el.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     x86@...nel.org, kirill.shutemov@...ux.intel.com,
        peterz@...radead.org, tony.luck@...el.com, tglx@...utronix.de,
        bp@...en8.de, mingo@...hat.com, hpa@...or.com, seanjc@...gle.com,
        pbonzini@...hat.com, rafael@...nel.org, david@...hat.com,
        dan.j.williams@...el.com, len.brown@...el.com, ak@...ux.intel.com,
        isaku.yamahata@...el.com, ying.huang@...el.com, chao.gao@...el.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, nik.borisov@...e.com,
        bagasdotme@...il.com, sagis@...gle.com, imammedo@...hat.com
Subject: Re: [PATCH v15 09/23] x86/virt/tdx: Get module global metadata for
 module initialization

On 11/9/23 03:55, Kai Huang wrote:
...> +	ret = read_sys_metadata_field16(MD_FIELD_ID_MAX_TDMRS,
> +			&tdmr_sysinfo->max_tdmrs);
> +	if (ret)
> +		return ret;
> +
> +	ret = read_sys_metadata_field16(MD_FIELD_ID_MAX_RESERVED_PER_TDMR,
> +			&tdmr_sysinfo->max_reserved_per_tdmr);
> +	if (ret)
> +		return ret;
> +
> +	ret = read_sys_metadata_field16(MD_FIELD_ID_PAMT_4K_ENTRY_SIZE,
> +			&tdmr_sysinfo->pamt_entry_size[TDX_PS_4K]);
> +	if (ret)
> +		return ret;
> +
> +	ret = read_sys_metadata_field16(MD_FIELD_ID_PAMT_2M_ENTRY_SIZE,
> +			&tdmr_sysinfo->pamt_entry_size[TDX_PS_2M]);
> +	if (ret)
> +		return ret;
> +
> +	return read_sys_metadata_field16(MD_FIELD_ID_PAMT_1G_ENTRY_SIZE,
> +			&tdmr_sysinfo->pamt_entry_size[TDX_PS_1G]);
> +}

I kinda despise how this looks.  It's impossible to read.

I'd much rather do something like the attached where you just map the
field number to a structure member.  Note that this kind of structure
could also be converted to leverage the bulk metadata query in the future.

Any objections to doing something more like the attached completely
untested patch?
View attachment "cleaner-tdx-metadata-0.patch" of type "text/x-patch" (2588 bytes)