Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 28 Jun 2023 15:04:19 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Kai Huang <kai.huang@intel.com>
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-mm@kvack.org, x86@kernel.org, dave.hansen@intel.com,
        kirill.shutemov@linux.intel.com, tony.luck@intel.com,
        tglx@linutronix.de, bp@alien8.de, mingo@redhat.com, hpa@zytor.com,
        seanjc@google.com, pbonzini@redhat.com, david@redhat.com,
        dan.j.williams@intel.com, rafael.j.wysocki@intel.com,
        ashok.raj@intel.com, reinette.chatre@intel.com,
        len.brown@intel.com, ak@linux.intel.com, isaku.yamahata@intel.com,
        ying.huang@intel.com, chao.gao@intel.com,
        sathyanarayanan.kuppuswamy@linux.intel.com, nik.borisov@suse.com,
        bagasdotme@gmail.com, sagis@google.com, imammedo@redhat.com
Subject: Re: [PATCH v12 07/22] x86/virt/tdx: Add skeleton to enable TDX on
 demand
Message-ID: <20230628130419.GC2438817@hirez.programming.kicks-ass.net>
References: <cover.1687784645.git.kai.huang@intel.com>
 <104d324cd68b12e14722ee5d85a660cccccd8892.1687784645.git.kai.huang@intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <104d324cd68b12e14722ee5d85a660cccccd8892.1687784645.git.kai.huang@intel.com>
Precedence: bulk

On Tue, Jun 27, 2023 at 02:12:37AM +1200, Kai Huang wrote:

> +static int try_init_module_global(void)
> +{
> +	unsigned long flags;
> +	int ret;
> +
> +	/*
> +	 * The TDX module global initialization only needs to be done
> +	 * once on any cpu.
> +	 */
> +	raw_spin_lock_irqsave(&tdx_global_init_lock, flags);
> +
> +	if (tdx_global_initialized) {
> +		ret = 0;
> +		goto out;
> +	}
> +
> +	/* All '0's are just unused parameters. */
> +	ret = seamcall(TDH_SYS_INIT, 0, 0, 0, 0, NULL, NULL);
> +	if (!ret)
> +		tdx_global_initialized = true;
> +out:
> +	raw_spin_unlock_irqrestore(&tdx_global_init_lock, flags);
> +
> +	return ret;
> +}

How long does that TDX_SYS_INIT take and why is a raw_spinlock with IRQs
disabled the right way to serialize this?