linux-kernel - Re: [PATCH v4] x86/paravirt: Disable virt spinlock on bare metal

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Message-ID: <Zqfjx6eI9F8sHi/p@chenyu5-mobl2>
Date: Tue, 30 Jul 2024 02:47:35 +0800
From: Chen Yu <yu.c.chen@...el.com>
To: Thomas Gleixner <tglx@...utronix.de>
CC: Dave Hansen <dave.hansen@...ux.intel.com>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, "Arnd
 Bergmann" <arnd@...db.de>, <virtualization@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, Juergen Gross <jgross@...e.com>, "Nikolay
 Borisov" <nik.borisov@...e.com>, Qiuxu Zhuo <qiuxu.zhuo@...el.com>, "Prem
 Nath Dey" <prem.nath.dey@...el.com>, Xiaoping Zhou <xiaoping.zhou@...el.com>
Subject: Re: [PATCH v4] x86/paravirt: Disable virt spinlock on bare metal

Hi Thomas,

On 2024-07-29 at 14:43:37 +0200, Thomas Gleixner wrote:
> On Mon, Jul 29 2024 at 14:52, Chen Yu wrote:
> >  #ifdef CONFIG_PARAVIRT
> >  /*
> > - * virt_spin_lock_key - enables (by default) the virt_spin_lock() hijack.
> > + * virt_spin_lock_key - disables (by default) the virt_spin_lock() hijack.
> >   *
> >   * Native (and PV wanting native due to vCPU pinning) should disable this key.
> >   * It is done in this backwards fashion to only have a single direction change,
> >   * which removes ordering between native_pv_spin_init() and HV setup.
> 
> This comment is bogus now.
>

Yes, now it could be two direction: enabled first and disabled later. Let me refine
the comments.

thanks,
Chenyu