linux-kernel - Re: [PATCH 2/2] x86/asm/delay: Introduce TPAUSE delay

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200226215928.GU160988@tassilo.jf.intel.com>
Date:   Wed, 26 Feb 2020 13:59:28 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     Kyung Min Park <kyung.min.park@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, gregkh@...uxfoundation.org, ashok.raj@...el.com,
        ravi.v.shankar@...el.com, fenghua.yu@...el.com
Subject: Re: [PATCH 2/2] x86/asm/delay: Introduce TPAUSE delay

On Wed, Feb 26, 2020 at 01:20:34PM -0800, Luck, Tony wrote:
> On Wed, Feb 26, 2020 at 01:10:40PM -0800, Andi Kleen wrote:
> > On Wed, Feb 26, 2020 at 11:10:58AM -0800, Kyung Min Park wrote:
> > > TPAUSE instructs the processor to enter an implementation-dependent
> > > optimized state. The instruction execution wakes up when the time-stamp
> > > counter reaches or exceeds the implicit EDX:EAX 64-bit input value.
> > > The instruction execution also wakes up due to the expiration of
> > > the operating system time-limit or by an external interrupt
> > 
> > This is actually a behavior change. Today's udelay() will continue
> > after processing the interrupt. Your patches don't
> 
> The instruction level TPAUSE is called inside delay_wait()
> that checks to see of we were interrupted early and loops to issue
> another TPAUSE if needed.

Ah right. It was already solved for mwaitx. Great.

-Andi