linux-kernel - Re: [PATCH 2/7] x86/cpufeatures: Enumerate ENQCMD and ENQCMDS instructions

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Date:   Mon, 27 Apr 2020 13:17:16 -0700
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Jacob Jun Pan <jacob.jun.pan@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Sohil Mehta <sohil.mehta@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        x86 <x86@...nel.org>, iommu@...ts.linux-foundation.org
Subject: Re: [PATCH 2/7] x86/cpufeatures: Enumerate ENQCMD and ENQCMDS
 instructions

On Sun, Apr 26, 2020 at 01:06:33PM +0200, Thomas Gleixner wrote:
> Fenghua Yu <fenghua.yu@...el.com> writes:
> > A user space application can execute ENQCMD instruction to submit work
> > to device. The kernel executes ENQCMDS instruction to submit work to
> > device.
> 
> So a user space application _can_ execute ENQCMD and the kernel
> executes ENQCMDS. And both submit work to device.
> 
> > There is a lot of other enabling needed for the instructions to actually
> > be usable in user space and the kernel, and that enabling is coming later
> > in the series and in device drivers.
> 
> That's important information to the enumeration of the instructions in
> which way?

I just want to notify people this enumeration is only part of enabling
ENQCMD. But seems this paragraph is not so useful to be here. Maybe I can
remove it.

Thanks.

-Fenghua