linux-kernel - Re: [PATCH v7 11/20] x86/virt/tdx: Add placeholder to construct TDMRs to cover all TDX memory regions

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Message-ID: <35aee96c1bb56322191ae442f3928d7dff064a92.camel@intel.com>
Date:   Thu, 24 Nov 2022 12:02:36 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "Luck, Tony" <tony.luck@...el.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "Gao, Chao" <chao.gao@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: [PATCH v7 11/20] x86/virt/tdx: Add placeholder to construct TDMRs
 to cover all TDX memory regions

On Wed, 2022-11-23 at 14:17 -0800, Dave Hansen wrote:
> First, I think 'tdx_sysinfo' should probably be a local variable in
> init_tdx_module() and have its address passed in here.  Having global
> variables always makes it more opaque about who is initializing it.

Sorry I missed to respond this.

Using local variable for 'tdx_sysinfo' will cause a build warning:

https://lore.kernel.org/lkml/a6694c81b4e96a22557fd0af70a81bd2c2e4e3e7.camel@intel.com/

So instead we can have a local variable for the pointer of 'tdx_sysinfo', and
dynamically allocate memory for it.

KVM will need to use it, though.  So I think eventually we will need to have a
global variable (either tdx_sysinfo itself, or the pointer of it).  But this can
be done in a separate patch.

CMRs can be done in the same way (KVM doesn't need to use CMRs, but perhaps some
day we may want to expose them to /sysfs, etc).

What's your preference?