linux-kernel - Re: [PATCH v5 1/3] x86/tdx: Add TDX Guest attestation interface driver

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Message-ID: <42e1af54bef03361c1a23dac8d1e4ffd8e66114a.camel@intel.com>
Date:   Wed, 04 May 2022 10:08:11 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Wander Costa <wander@...hat.com>
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>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        marcelo.cerri@...onical.com, tim.gardner@...onical.com,
        khalid.elmously@...onical.com, philip.cox@...onical.com,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 1/3] x86/tdx: Add TDX Guest attestation interface
 driver

On Tue, 2022-05-03 at 08:09 -0700, Sathyanarayanan Kuppuswamy wrote:
> 
> On 5/3/22 7:38 AM, Wander Costa wrote:
> > > I don't want to pollute the dmesg logs if possible. For IOCTL use case,
> > > the return value can be used to understand the failure reason from user
> > > code. But for initcall failure, pr_err message is required to understand
> > > the failure reason.
> > How often is this call expected to fail?
> 
> In general, it should not fail (so very low fail frequency). But the
> point is, we can easily understand this failure from user end. So we
> don't need to print more in non-debug environment.
> 
> > 

To support your statement, all the error codes return to userspace need to be
clearly documented around the IOCTL in the uapi header.  But I think you have to
do this anyway.

-- 
Thanks,
-Kai