Message-ID: <2d9172c5-e1e7-bf94-c52b-0e9bc5b5b319@intel.com>
Date:   Mon, 13 Feb 2023 10:07:30 -0800
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Subject: Re: [PATCH v9 07/18] x86/virt/tdx: Do TDX module per-cpu
 initialization
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To:     Kai Huang <kai.huang@intel.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Cc:     linux-mm@kvack.org, peterz@infradead.org, tglx@linutronix.de,
        seanjc@google.com, pbonzini@redhat.com, dan.j.williams@intel.com,
        rafael.j.wysocki@intel.com, kirill.shutemov@linux.intel.com,
        ying.huang@intel.com, reinette.chatre@intel.com,
        len.brown@intel.com, tony.luck@intel.com, ak@linux.intel.com,
        isaku.yamahata@intel.com, chao.gao@intel.com,
        sathyanarayanan.kuppuswamy@linux.intel.com, david@redhat.com,
        bagasdotme@gmail.com, sagis@google.com, imammedo@redhat.com
References: <cover.1676286526.git.kai.huang@intel.com>
 <557c526a1190903d11d67c4e2c76e01f67f6eb15.1676286526.git.kai.huang@intel.com>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <557c526a1190903d11d67c4e2c76e01f67f6eb15.1676286526.git.kai.huang@intel.com>
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Precedence: bulk

On 2/13/23 03:59, Kai Huang wrote:
> @@ -247,8 +395,17 @@ int tdx_enable(void)
>  		ret = __tdx_enable();
>  		break;
>  	case TDX_MODULE_INITIALIZED:
> -		/* Already initialized, great, tell the caller. */
> -		ret = 0;
> +		/*
> +		 * The previous call of __tdx_enable() may only have
> +		 * initialized part of present cpus during module
> +		 * initialization, and new cpus may have become online
> +		 * since then.
> +		 *
> +		 * To make sure all online cpus are TDX-runnable, always
> +		 * do per-cpu initialization for all online cpus here
> +		 * even the module has been initialized.
> +		 */
> +		ret = __tdx_enable_online_cpus();

I'm missing something here.  CPUs get initialized through either:

 1. __tdx_enable(), for the CPUs around at the time
 2. tdx_cpu_online(), for hotplugged CPUs after __tdx_enable()

But, this is a third class.  CPUs that came online after #1, but which
got missed by #2.  How can that happen?