linux-kernel - Re: [PATCH v12 07/22] x86/virt/tdx: Add skeleton to enable TDX on demand

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Message-ID: <20230630092232.GB2533791@hirez.programming.kicks-ass.net>
Date:   Fri, 30 Jun 2023 11:22:32 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Huang, Kai" <kai.huang@...el.com>
Cc:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "david@...hat.com" <david@...hat.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
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        "Shahar, Sagi" <sagis@...gle.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "Gao, Chao" <chao.gao@...el.com>
Subject: Re: [PATCH v12 07/22] x86/virt/tdx: Add skeleton to enable TDX on
 demand

On Thu, Jun 29, 2023 at 12:15:13AM +0000, Huang, Kai wrote:

> > 	Can be called locally or through an IPI function call.
> > 
> 
> Thanks.  As in another reply, if using spinlock is OK, then I think we can say
> it will be called either locally or through an IPI function call.  Otherwise, we
> do via a new separate function tdx_global_init() and no lock is needed in that
> function.  The caller should call it properly.

IPI must use raw_spinlock_t. I'm ok with using raw_spinlock_t if there's
actual need for that, but the code as presented didn't -- in comments or
otherwise -- make it clear why it was as it was.

TDX not specifying time constraints on the various TD/SEAM-CALLs is
ofcourse sad, but alas.