linux-kernel - Re: [PATCH v17 016/116] x86/virt/tdx: Add a helper function to return system wide info about TDX module

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Message-ID: <21c7fda2f6f9a320cb7cb0ae8c42ca4ab47adc70.camel@intel.com>
Date:   Mon, 11 Dec 2023 22:38:20 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>
CC:     "Zhang, Tina" <tina.zhang@...el.com>,
        "seanjc@...gle.com" <seanjc@...gle.com>,
        "Yuan, Hang" <hang.yuan@...el.com>,
        "Chen, Bo2" <chen.bo@...el.com>,
        "sagis@...gle.com" <sagis@...gle.com>,
        "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
        "Aktas, Erdem" <erdemaktas@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "zhi.wang.linux@...il.com" <zhi.wang.linux@...il.com>
Subject: Re: [PATCH v17 016/116] x86/virt/tdx: Add a helper function to return
 system wide info about TDX module

On Tue, 2023-11-07 at 06:55 -0800, Yamahata, Isaku wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
> 
> TDX KVM needs system-wide information about the TDX module, struct
> tdsysinfo_struct.  Add a helper function tdx_get_sysinfo() to return it
> instead of KVM getting it with various error checks.  Make KVM call the
> function and stash the info.  Move out the struct definition about it to
> common place arch/x86/include/asm/tdx.h.
> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>  arch/x86/include/asm/tdx.h  | 59 +++++++++++++++++++++++++++++++++++++
>  arch/x86/kvm/vmx/tdx.c      | 15 +++++++++-
>  arch/x86/virt/vmx/tdx/tdx.c | 20 +++++++++++--
>  arch/x86/virt/vmx/tdx/tdx.h | 51 --------------------------------
>  4 files changed, 91 insertions(+), 54 deletions(-)
> 
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index 3b648f290af3..276bdae47738 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -109,6 +109,62 @@ static inline u64 sc_retry(sc_func_t func, u64 fn,
>  #define seamcall_ret(_fn, _args)	sc_retry(__seamcall_ret, (_fn), (_args))
>  #define seamcall_saved_ret(_fn, _args)	sc_retry(__seamcall_saved_ret, (_fn), (_args))
>  
> +struct tdx_cpuid_config {
> +	__struct_group(tdx_cpuid_config_leaf, leaf_sub_leaf, __packed,
> +		u32 leaf;
> +		u32 sub_leaf;
> +	);
> +	__struct_group(tdx_cpuid_config_value, value, __packed,
> +		u32 eax;
> +		u32 ebx;
> +		u32 ecx;
> +		u32 edx;
> +	);
> +} __packed;
> +
> +#define TDSYSINFO_STRUCT_SIZE		1024
> +#define TDSYSINFO_STRUCT_ALIGNMENT	1024
> +
> +/*
> + * The size of this structure itself is flexible.  The actual structure
> + * passed to TDH.SYS.INFO must be padded to TDSYSINFO_STRUCT_SIZE bytes
> + * and TDSYSINFO_STRUCT_ALIGNMENT bytes aligned.
> + */
> +struct tdsysinfo_struct {
> +	/* TDX-SEAM Module Info */
> +	u32	attributes;
> +	u32	vendor_id;
> +	u32	build_date;
> +	u16	build_num;
> +	u16	minor_version;
> +	u16	major_version;
> +	u8	reserved0[14];
> +	/* Memory Info */
> +	u16	max_tdmrs;
> +	u16	max_reserved_per_tdmr;
> +	u16	pamt_entry_size;
> +	u8	reserved1[10];
> +	/* Control Struct Info */
> +	u16	tdcs_base_size;
> +	u8	reserved2[2];
> +	u16	tdvps_base_size;
> +	u8	tdvps_xfam_dependent_size;
> +	u8	reserved3[9];
> +	/* TD Capabilities */
> +	u64	attributes_fixed0;
> +	u64	attributes_fixed1;
> +	u64	xfam_fixed0;
> +	u64	xfam_fixed1;
> +	u8	reserved4[32];
> +	u32	num_cpuid_config;
> +	/*
> +	 * The actual number of CPUID_CONFIG depends on above
> +	 * 'num_cpuid_config'.
> +	 */
> +	DECLARE_FLEX_ARRAY(struct tdx_cpuid_config, cpuid_configs);
> +} __packed;
> +
> +const struct tdsysinfo_struct *tdx_get_sysinfo(void);
> 

With the lastest TDX host code I don't think we need TDSYSINFO_STRUCT anymore.

I think it makes more sense to modify the TDX host code to expose an
infrastructure to read TDX module global metadata and KVM can just use that to
get what it wants to create/run TDX guests.

I am working on these patches and I'll update to you when done (should be soon).