linux-kernel - Re: [PATCH v12 16/22] x86/virt/tdx: Initialize all TDMRs

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Message-ID: <20230706053158.73plfugwqvwwkdeo@yy-desk-7060>
Date:   Thu, 6 Jul 2023 13:31:58 +0800
From:   Yuan Yao <yuan.yao@...ux.intel.com>
To:     Kai Huang <kai.huang@...el.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-mm@...ck.org, x86@...nel.org, dave.hansen@...el.com,
        kirill.shutemov@...ux.intel.com, tony.luck@...el.com,
        peterz@...radead.org, tglx@...utronix.de, bp@...en8.de,
        mingo@...hat.com, hpa@...or.com, seanjc@...gle.com,
        pbonzini@...hat.com, david@...hat.com, dan.j.williams@...el.com,
        rafael.j.wysocki@...el.com, ashok.raj@...el.com,
        reinette.chatre@...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 v12 16/22] x86/virt/tdx: Initialize all TDMRs

On Tue, Jun 27, 2023 at 02:12:46AM +1200, Kai Huang wrote:
> After the global KeyID has been configured on all packages, initialize
> all TDMRs to make all TDX-usable memory regions that are passed to the
> TDX module become usable.
>
> This is the last step of initializing the TDX module.
>
> Initializing TDMRs can be time consuming on large memory systems as it
> involves initializing all metadata entries for all pages that can be
> used by TDX guests.  Initializing different TDMRs can be parallelized.
> For now to keep it simple, just initialize all TDMRs one by one.  It can
> be enhanced in the future.

Reviewed-by: Yuan Yao <yuan.yao@...el.com>

>
> Signed-off-by: Kai Huang <kai.huang@...el.com>
> Reviewed-by: Isaku Yamahata <isaku.yamahata@...el.com>
> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>
> v11 -> v12:
>  - Added Kirill's tag
>
> v10 -> v11:
>  - No update
>
> v9 -> v10:
>  - Code change due to change static 'tdx_tdmr_list' to local 'tdmr_list'.
>
> v8 -> v9:
>  - Improved changlog to explain why initializing TDMRs can take long
>    time (Dave).
>  - Improved comments around 'next-to-initialize' address (Dave).
>
> v7 -> v8: (Dave)
>  - Changelog:
>    - explicitly call out this is the last step of TDX module initialization.
>    - Trimed down changelog by removing SEAMCALL name and details.
>  - Removed/trimmed down unnecessary comments.
>  - Other changes due to 'struct tdmr_info_list'.
>
> v6 -> v7:
>  - Removed need_resched() check. -- Andi.
>
>
> ---
>  arch/x86/virt/vmx/tdx/tdx.c | 60 ++++++++++++++++++++++++++++++++-----
>  arch/x86/virt/vmx/tdx/tdx.h |  1 +
>  2 files changed, 53 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index f5d4dbc11aee..52b7267ea226 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -994,6 +994,56 @@ static int config_global_keyid(void)
>  	return ret;
>  }
>
> +static int init_tdmr(struct tdmr_info *tdmr)
> +{
> +	u64 next;
> +
> +	/*
> +	 * Initializing a TDMR can be time consuming.  To avoid long
> +	 * SEAMCALLs, the TDX module may only initialize a part of the
> +	 * TDMR in each call.
> +	 */
> +	do {
> +		struct tdx_module_output out;
> +		int ret;
> +
> +		/* All 0's are unused parameters, they mean nothing. */
> +		ret = seamcall(TDH_SYS_TDMR_INIT, tdmr->base, 0, 0, 0, NULL,
> +				&out);
> +		if (ret)
> +			return ret;
> +		/*
> +		 * RDX contains 'next-to-initialize' address if
> +		 * TDH.SYS.TDMR.INIT did not fully complete and
> +		 * should be retried.
> +		 */
> +		next = out.rdx;
> +		cond_resched();
> +		/* Keep making SEAMCALLs until the TDMR is done */
> +	} while (next < tdmr->base + tdmr->size);
> +
> +	return 0;
> +}
> +
> +static int init_tdmrs(struct tdmr_info_list *tdmr_list)
> +{
> +	int i;
> +
> +	/*
> +	 * This operation is costly.  It can be parallelized,
> +	 * but keep it simple for now.
> +	 */
> +	for (i = 0; i < tdmr_list->nr_consumed_tdmrs; i++) {
> +		int ret;
> +
> +		ret = init_tdmr(tdmr_entry(tdmr_list, i));
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
>  static int init_tdx_module(void)
>  {
>  	struct tdsysinfo_struct *sysinfo;
> @@ -1067,14 +1117,8 @@ static int init_tdx_module(void)
>  	if (ret)
>  		goto out_reset_pamts;
>
> -	/*
> -	 * TODO:
> -	 *
> -	 *  - Initialize all TDMRs.
> -	 *
> -	 *  Return error before all steps are done.
> -	 */
> -	ret = -EINVAL;
> +	/* Initialize TDMRs to complete the TDX module initialization */
> +	ret = init_tdmrs(&tdmr_list);
>  out_reset_pamts:
>  	if (ret) {
>  		/*
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index a0438513bec0..f6b4e153890d 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -25,6 +25,7 @@
>  #define TDH_SYS_INFO		32
>  #define TDH_SYS_INIT		33
>  #define TDH_SYS_LP_INIT		35
> +#define TDH_SYS_TDMR_INIT	36
>  #define TDH_SYS_CONFIG		45
>
>  struct cmr_info {
> --
> 2.40.1
>