linux-kernel - Re: [PATCH v1 09/31] x86/resctrl: Add a resctrl helper to reset all the resources

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Message-ID: <ZhlepqX41cBsQh/m@e133380.arm.com>
Date: Fri, 12 Apr 2024 17:17:42 +0100
From: Dave Martin <Dave.Martin@....com>
To: "Shaopeng Tan (Fujitsu)" <tan.shaopeng@...itsu.com>
Cc: 'James Morse' <james.morse@....com>, "x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Reinette Chatre <reinette.chatre@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	H Peter Anvin <hpa@...or.com>, Babu Moger <Babu.Moger@....com>,
	"shameerali.kolothum.thodi@...wei.com" <shameerali.kolothum.thodi@...wei.com>,
	D Scott Phillips OS <scott@...amperecomputing.com>,
	"carl@...amperecomputing.com" <carl@...amperecomputing.com>,
	"lcherian@...vell.com" <lcherian@...vell.com>,
	"bobo.shaobowang@...wei.com" <bobo.shaobowang@...wei.com>,
	"baolin.wang@...ux.alibaba.com" <baolin.wang@...ux.alibaba.com>,
	Jamie Iles <quic_jiles@...cinc.com>,
	Xin Hao <xhao@...ux.alibaba.com>,
	"peternewman@...gle.com" <peternewman@...gle.com>,
	"dfustini@...libre.com" <dfustini@...libre.com>,
	"amitsinght@...vell.com" <amitsinght@...vell.com>,
	David Hildenbrand <david@...hat.com>,
	Rex Nie <rex.nie@...uarmicro.com>
Subject: Re: [PATCH v1 09/31] x86/resctrl: Add a resctrl helper to reset all
 the resources

On Wed, Apr 03, 2024 at 07:52:42AM +0000, Shaopeng Tan (Fujitsu) wrote:
> Hello James,
> 
> > On umount(), resctrl resets each resource back to its default configuration. It
> > only ever does this for all resources in one go.
> > 
> > reset_all_ctrls() is architecture specific as it works with struct
> > rdt_hw_resource.
> > 
> > Add an architecture helper to reset all resources.
> > 
> > Signed-off-by: James Morse <james.morse@....com>
> > ---
> >  arch/x86/include/asm/resctrl.h         |  2 ++
> >  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 16 +++++++++++-----
> >  2 files changed, 13 insertions(+), 5 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
> > index f61382258743..5f6a5375bb4a 100644
> > --- a/arch/x86/include/asm/resctrl.h
> > +++ b/arch/x86/include/asm/resctrl.h
> > @@ -15,6 +15,8 @@
> >   */
> >  #define X86_RESCTRL_EMPTY_CLOSID         ((u32)~0)
> > 
> > +void resctrl_arch_reset_resources(void);
> > +
> >  /**
> >   * struct resctrl_pqr_state - State cache for the PQR MSR
> >   * @cur_rmid:		The cached Resource Monitoring ID
> > diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > index 1a49c9918f8d..13c24cb18d76 100644
> > --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> > @@ -2859,6 +2859,14 @@ static int reset_all_ctrls(struct rdt_resource *r)
> >  	return 0;
> >  }
> > 
> > +void resctrl_arch_reset_resources(void)
> > +{
> > +	struct rdt_resource *r;
> > +
> > +	for_each_capable_rdt_resource(r)
> Could you explain why not "for_each_alloc_capable_rdt_resource(r)"?
> 
> > +		reset_all_ctrls(r);
> > +}
> > +
> >  /*
> >   * Move tasks from one to the other group. If @from is NULL, then all tasks
> >   * in the systems are moved unconditionally (used for teardown).
> > @@ -2968,16 +2976,14 @@ static void rmdir_all_sub(void)
> > 
> >  static void rdt_kill_sb(struct super_block *sb)  {
> > -	struct rdt_resource *r;
> > -
> >  	cpus_read_lock();
> >  	mutex_lock(&rdtgroup_mutex);
> > 
> >  	rdt_disable_ctx();
> > 
> > -	/*Put everything back to default values. */
> > -	for_each_alloc_capable_rdt_resource(r)
> This was "for_each_alloc_capable_rdt_resource(r)".
> 
> Best regards, 
> Shaopeng TAN

Noted for James to take a look at, thanks.

If this was intentional, it probably needs more explanation -- it looks
quite likely to have been unintentional, though.

Cheers
---Dave