linux-kernel - Re: [PATCH 2/3] x86/cpufeatures: Add WBNOINVD cpufeature

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Message-ID: <alpine.DEB.2.21.1803151015330.1525@nanos.tec.linutronix.de>
Date:   Thu, 15 Mar 2018 10:17:08 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
cc:     Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: [PATCH 2/3] x86/cpufeatures: Add WBNOINVD cpufeature

On Fri, 19 Jan 2018, Kirill A. Shutemov wrote:

> CPUID.0x80000008:EBX[9] indicates whether CPU supports WBNOINVD
> instruction.
> 
> The WBNOINVD instruction writes back all modified cache lines in the
> processor’s internal cache to main memory and does not invalidate
> (flush) the internal caches.

That's describing what that instruction does. Could you please explain why
this is useful and what kind of usage you envision for that.

Thanks,

	tglx