linux-kernel - Re: [PATCH v5 3/3] x86/tdx: Add Quote generation support

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Message-ID: <44c001bc83efa58df7cd8f67cd1fb0916e8a3e9d.camel@intel.com>
Date:   Wed, 04 May 2022 10:13:05 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Wander Lairson Costa <wander@...hat.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/3] x86/tdx: Add Quote generation support

On Mon, 2022-05-02 at 19:39 -0700, Sathyanarayanan Kuppuswamy wrote:
> > 
> > Using vmap() we can still (almost) avoid private/shared conversion at IOCTL
> > time
> > by allocating a default size buffer (which is large enough to cover 99%
> > cases,
> > etc) at driver initialization time:
> 
> Allocating fixed size buffer pool will work for dma buffer allocation
> as well.
> 
> So the comparison is between platform driver boilerplate code vs vmap
> and shared/unshared code addition. It is arguable which is better. I
> think it is about preference.

Not really.  DMA buffer is guaranteed to be shared for now, but it's not
guaranteed in the future generations of TDX.

-- 
Thanks,
-Kai