linux-kernel - Re: [PATCH v6 01/21] x86/tdx: Use enum to define page level of TDX supported page sizes

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Date:   Thu, 27 Oct 2022 08:27:06 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Kai Huang <kai.huang@...el.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     linux-mm@...ck.org, seanjc@...gle.com, pbonzini@...hat.com,
        dan.j.williams@...el.com, rafael.j.wysocki@...el.com,
        kirill.shutemov@...ux.intel.com, reinette.chatre@...el.com,
        len.brown@...el.com, tony.luck@...el.com, peterz@...radead.org,
        ak@...ux.intel.com, isaku.yamahata@...el.com, chao.gao@...el.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, bagasdotme@...il.com,
        sagis@...gle.com, imammedo@...hat.com
Subject: Re: [PATCH v6 01/21] x86/tdx: Use enum to define page level of TDX
 supported page sizes

On 10/26/22 16:16, Kai Huang wrote:
> +/*
> + * Get the TDX page level based on the kernel page level.  The caller
> + * to make sure only pass 4K/2M/1G kernel page level.
> + */
> +static inline enum tdx_pg_level to_tdx_pg_level(enum pg_level pglvl)
> +{
> +	switch (pglvl) {
> +	case PG_LEVEL_4K:
> +		return TDX_PG_LEVEL_4K;
> +	case PG_LEVEL_2M:
> +		return TDX_PG_LEVEL_2M;
> +	case PG_LEVEL_1G:
> +		return TDX_PG_LEVEL_1G;
> +	default:
> +		WARN_ON_ONCE(1);
> +	}
> +	return TDX_PG_LEVEL_NUM;
> +}

Is TDX_PG_LEVEL_NUM part of the ABI?  Or, is this going to accidentally
pass a whacky value to the SEAM module?

This needs something like this at the call-site:

	page_size = to_tdx_pg_level(pg_level);
	if (page_size >= TDX_PG_LEVEL_NUM)
		return false;