Message-ID: <66b19dc6ddbcf_4fc7294fd@dwillia2-xfh.jf.intel.com.notmuch>
Date: Mon, 5 Aug 2024 20:51:34 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: Kai Huang <kai.huang@...el.com>, <dave.hansen@...el.com>,
	<kirill.shutemov@...ux.intel.com>, <bp@...en8.de>, <tglx@...utronix.de>,
	<peterz@...radead.org>, <mingo@...hat.com>, <hpa@...or.com>,
	<seanjc@...gle.com>, <pbonzini@...hat.com>, <dan.j.williams@...el.com>
CC: <x86@...nel.org>, <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<rick.p.edgecombe@...el.com>, <isaku.yamahata@...el.com>,
	<chao.gao@...el.com>, <binbin.wu@...ux.intel.com>, <kai.huang@...el.com>
Subject: Re: [PATCH v2 07/10] x86/virt/tdx: Start to track all global
 metadata in one structure

Kai Huang wrote:
> The TDX module provides a set of "global metadata fields".  They report
> things like TDX module version, supported features, and fields related
> to create/run TDX guests and so on.
> 
> Currently the kernel only reads "TD Memory Region" (TDMR) related fields
> for module initialization.  There are immediate needs which require the
> TDX module initialization to read more global metadata including module
> version, supported features and "Convertible Memory Regions" (CMRs).
> 
> Also, KVM will need to read more metadata fields to support baseline TDX
> guests.  In the longer term, other TDX features like TDX Connect (which
> supports assigning trusted IO devices to TDX guest) may also require
> other kernel components such as pci/vt-d to access global metadata.
> 
> To meet all those requirements, the idea is the TDX host core-kernel to
> to provide a centralized, canonical, and read-only structure for the
> global metadata that comes out from the TDX module for all kernel
> components to use.
> 
> As the first step, introduce a new 'struct tdx_sysinfo' to track all
> global metadata fields.
> 
> TDX categories global metadata fields into different "Class"es.  E.g.,
> the current TDMR related fields are under class "TDMR Info".  Instead of
> making 'struct tdx_sysinfo' a plain structure to contain all metadata
> fields, organize them in smaller structures based on the "Class".
> 
> This allows those metadata fields to be used in finer granularity thus
> makes the code more clear.  E.g., the current construct_tdmr() can just
> take the structure which contains "TDMR Info" metadata fields.
> 
> Start with moving 'struct tdx_tdmr_sysinfo' to 'struct tdx_sysinfo', and
> rename 'struct tdx_tdmr_sysinfo' to 'struct tdx_sysinfo_tdmr_info' to
> make it consistent with the "class name".

How about 'struct tdx_sys_info' and 'struct tdx_sys_tdmr_info' to avoid
duplicating 'info' in the symbol name?

Do pure renames indpendent of logic changes to make patches like
this easier to read.

I would also move the pure rename to the front of the patches so the
reviewer spends as minimal amount of time with the deprecated name in
the set.

> Add a new function get_tdx_sysinfo() as the place to read all metadata
> fields, and call it at the beginning of init_tdx_module().  Move the
> existing get_tdx_tdmr_sysinfo() to get_tdx_sysinfo().
> 
> Note there is a functional change: get_tdx_tdmr_sysinfo() is moved from
> after build_tdx_memlist() to before it, but it is fine to do so.
> 
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> ---
>  arch/x86/virt/vmx/tdx/tdx.c | 29 +++++++++++++++++------------
>  arch/x86/virt/vmx/tdx/tdx.h | 32 +++++++++++++++++++++++++-------
>  2 files changed, 42 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index 86c47db64e42..3253cdfa5207 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -320,11 +320,11 @@ 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)
> +	TD_SYSINFO_MAP(_field_id, struct tdx_sysinfo_tdmr_info, _member)
>  
> -static int get_tdx_tdmr_sysinfo(struct tdx_tdmr_sysinfo *tdmr_sysinfo)
> +static int get_tdx_tdmr_sysinfo(struct tdx_sysinfo_tdmr_info *tdmr_sysinfo)
>  {
> -	/* Map TD_SYSINFO fields into 'struct tdx_tdmr_sysinfo': */
> +	/* Map TD_SYSINFO fields into 'struct tdx_sysinfo_tdmr_info': */
>  	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),
> @@ -337,6 +337,11 @@ static int get_tdx_tdmr_sysinfo(struct tdx_tdmr_sysinfo *tdmr_sysinfo)
>  	return stbuf_read_sysmd_multi(fields, ARRAY_SIZE(fields), tdmr_sysinfo);
>  }
>  
> +static int get_tdx_sysinfo(struct tdx_sysinfo *sysinfo)
> +{
> +	return get_tdx_tdmr_sysinfo(&sysinfo->tdmr_info);
> +}
> +
>  /* Calculate the actual TDMR size */
>  static int tdmr_size_single(u16 max_reserved_per_tdmr)
>  {
> @@ -353,7 +358,7 @@ static int tdmr_size_single(u16 max_reserved_per_tdmr)
>  }
>  
>  static int alloc_tdmr_list(struct tdmr_info_list *tdmr_list,
> -			   struct tdx_tdmr_sysinfo *tdmr_sysinfo)
> +			   struct tdx_sysinfo_tdmr_info *tdmr_sysinfo)
>  {
>  	size_t tdmr_sz, tdmr_array_sz;
>  	void *tdmr_array;
> @@ -936,7 +941,7 @@ static int tdmrs_populate_rsvd_areas_all(struct tdmr_info_list *tdmr_list,
>   */
>  static int construct_tdmrs(struct list_head *tmb_list,
>  			   struct tdmr_info_list *tdmr_list,
> -			   struct tdx_tdmr_sysinfo *tdmr_sysinfo)
> +			   struct tdx_sysinfo_tdmr_info *tdmr_sysinfo)
>  {
>  	int ret;
>  
> @@ -1109,9 +1114,13 @@ static int init_tdmrs(struct tdmr_info_list *tdmr_list)
>  
>  static int init_tdx_module(void)
>  {
> -	struct tdx_tdmr_sysinfo tdmr_sysinfo;
> +	struct tdx_sysinfo sysinfo;
>  	int ret;
>  
> +	ret = get_tdx_sysinfo(&sysinfo);
> +	if (ret)
> +		return ret;
> +
>  	/*
>  	 * To keep things simple, assume that all TDX-protected memory
>  	 * will come from the page allocator.  Make sure all pages in the
> @@ -1128,17 +1137,13 @@ static int init_tdx_module(void)
>  	if (ret)
>  		goto out_put_tdxmem;
>  
> -	ret = get_tdx_tdmr_sysinfo(&tdmr_sysinfo);
> -	if (ret)
> -		goto err_free_tdxmem;
> -
>  	/* Allocate enough space for constructing TDMRs */
> -	ret = alloc_tdmr_list(&tdx_tdmr_list, &tdmr_sysinfo);
> +	ret = alloc_tdmr_list(&tdx_tdmr_list, &sysinfo.tdmr_info);
>  	if (ret)
>  		goto err_free_tdxmem;
>  
>  	/* Cover all TDX-usable memory regions in TDMRs */
> -	ret = construct_tdmrs(&tdx_memlist, &tdx_tdmr_list, &tdmr_sysinfo);
> +	ret = construct_tdmrs(&tdx_memlist, &tdx_tdmr_list, &sysinfo.tdmr_info);
>  	if (ret)
>  		goto err_free_tdmrs;
>  
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index 4e43cec19917..b5eb7c35f1dc 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -100,13 +100,6 @@ struct tdx_memblock {
>  	int nid;
>  };
>  
> -/* "TDMR info" part of "Global Scope Metadata" for constructing TDMRs */
> -struct tdx_tdmr_sysinfo {
> -	u16 max_tdmrs;
> -	u16 max_reserved_per_tdmr;
> -	u16 pamt_entry_size[TDX_PS_NR];
> -};
> -
>  /* Warn if kernel has less than TDMR_NR_WARN TDMRs after allocation */
>  #define TDMR_NR_WARN 4
>  
> @@ -119,4 +112,29 @@ struct tdmr_info_list {
>  	int max_tdmrs;	/* How many 'tdmr_info's are allocated */
>  };
>  
> +/*
> + * Kernel-defined structures to contain "Global Scope Metadata".
> + *
> + * TDX global metadata fields are categorized by "Class".  See the
> + * "global_metadata.json" in the "TDX 1.5 ABI Definitions".
> + *
> + * 'struct tdx_sysinfo' is the main structure to contain all metadata
> + * used by the kernel.  It contains sub-structures with each reflecting
> + * the "Class" in the 'global_metadata.json'.
> + *
> + * Note not all metadata fields in each class are defined, only those
> + * used by the kernel are.
> + */
> +
> +/* Class "TDMR Info" */
> +struct tdx_sysinfo_tdmr_info {
> +	u16 max_tdmrs;
> +	u16 max_reserved_per_tdmr;
> +	u16 pamt_entry_size[TDX_PS_NR];
> +};
> +
> +struct tdx_sysinfo {
> +	struct tdx_sysinfo_tdmr_info tdmr_info;
> +};

I would just call this member 'tdmr' since the 'info' is already applied
by being in tdx_sys_info.

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