linux-kernel - RE: [PATCH v9 07/18] x86/virt/tdx: Do TDX module per-cpu initialization

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Date:   Mon, 13 Feb 2023 21:19:07 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "Hansen, Dave" <dave.hansen@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "Gao, Chao" <chao.gao@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "david@...hat.com" <david@...hat.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>
Subject: RE: [PATCH v9 07/18] x86/virt/tdx: Do TDX module per-cpu
 initialization

> On 2/13/23 03:59, Kai Huang wrote:
> > To avoid duplicated code, add a
> > helper to call SEAMCALL on all online cpus one by one but with a skip
> > function to check whether to skip certain cpus, and use that helper to
> > do the per-cpu initialization.
> ...
> > +/*
> > + * Call @func on all online cpus one by one but skip those cpus
> > + * when @skip_func is valid and returns true for them.
> > + */
> > +static int tdx_on_each_cpu_cond(int (*func)(void *), void *func_data,
> > +				bool (*skip_func)(int cpu, void *),
> > +				void *skip_data)
> 
> I only see one caller of this.  Where is the duplicated code?

The other caller is in patch 15 (x86/virt/tdx: Configure global KeyID on all packages).

I kinda mentioned this in the changelog:

	" Similar to the per-cpu module initialization, a later step to config the key for the global KeyID..."

If we don't have this helper, then we can end up with having below loop in two functions:

	for_each_online(cpu) {
		if (should_skip(cpu))
			continue;

		// call @func on @cpu.
	}