linux-kernel - Re: [PATCH v11 08/20] x86/virt/tdx: Get information about TDX module and TDX-capable memory

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Message-ID: <20230609013346.GN2244082@ls.amr.corp.intel.com>
Date:   Thu, 8 Jun 2023 18:33:46 -0700
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
Cc:     Isaku Yamahata <isaku.yamahata@...il.com>,
        "Huang, Kai" <kai.huang@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "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>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "Luck, Tony" <tony.luck@...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 v11 08/20] x86/virt/tdx: Get information about TDX module
 and TDX-capable memory

On Fri, Jun 09, 2023 at 02:54:41AM +0300,
"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com> wrote:

> On Thu, Jun 08, 2023 at 04:29:19PM -0700, Isaku Yamahata wrote:
> > On Thu, Jun 08, 2023 at 02:41:28PM +0300,
> > "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com> wrote:
> > 
> > > On Thu, Jun 08, 2023 at 02:40:27AM +0000, Huang, Kai wrote:
> > > > On Thu, 2023-06-08 at 03:27 +0300, kirill.shutemov@...ux.intel.com wrote:
> > > > > On Mon, Jun 05, 2023 at 02:27:21AM +1200, Kai Huang wrote:
> > > > > > For now both 'tdsysinfo_struct' and CMRs are only used during the module
> > > > > > initialization.  But because they are both relatively big, declare them
> > > > > > inside the module initialization function but as static variables.
> > > > > 
> > > > > This justification does not make sense to me. static variables will not be
> > > > > freed after function returned. They will still consume memory.
> > > > > 
> > > > > I think you need to allocate/free memory dynamically, if they are too big
> > > > > for stack.
> > > > 
> > > > 
> > > > I do need to keep tdsysinfo_struct as it will be used by KVM too.
> > > 
> > > Will you pass it down to KVM from this function? Will KVM use the struct
> > > after the function returns?
> > 
> > KVM needs tdsysinfo_struct to create guest TD.  It doesn't require
> > 1024-alignment.
> 
> How KVM gets it from here?

For now, TDX KVM patch series moves the tdsysinfo out of the function, and add
a getter function of it.
As long as KVM can access the info, it doesn't care how its memory is allocated.
static or dynamic.
-- 
Isaku Yamahata <isaku.yamahata@...il.com>