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Subject: Re: [PATCH v5 3/3] x86/tdx: Add Quote generation support
From:   Kai Huang <kai.huang@intel.com>
To:     Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H . Peter Anvin" <hpa@zytor.com>,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Andi Kleen <ak@linux.intel.com>,
        Wander Lairson Costa <wander@redhat.com>,
        Isaku Yamahata <isaku.yamahata@gmail.com>,
        marcelo.cerri@canonical.com, tim.gardner@canonical.com,
        khalid.elmously@canonical.com, philip.cox@canonical.com,
        linux-kernel@vger.kernel.org
Date:   Wed, 04 May 2022 10:13:05 +1200
In-Reply-To: <ac299f99-7ef6-7fc2-a9fe-7ed2586b9b09@linux.intel.com>
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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