linux-kernel - Re: [RFC PATCH 20/36] arm_mpam: Probe the hardware features resctrl supports

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20250728171628.00001cd3@huawei.com>
Date: Mon, 28 Jul 2025 17:16:28 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Ben Horgan <ben.horgan@....com>
CC: James Morse <james.morse@....com>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, Rob Herring <robh@...nel.org>, "Rohit
 Mathew" <rohit.mathew@....com>, Shanker Donthineni <sdonthineni@...dia.com>,
	Zeng Heng <zengheng4@...wei.com>, Lecopzer Chen <lecopzerc@...dia.com>, Carl
 Worth <carl@...amperecomputing.com>, <shameerali.kolothum.thodi@...wei.com>,
	D Scott Phillips OS <scott@...amperecomputing.com>, <lcherian@...vell.com>,
	<bobo.shaobowang@...wei.com>, <tan.shaopeng@...itsu.com>,
	<baolin.wang@...ux.alibaba.com>, Jamie Iles <quic_jiles@...cinc.com>, Xin Hao
	<xhao@...ux.alibaba.com>, <peternewman@...gle.com>, <dfustini@...libre.com>,
	<amitsinght@...vell.com>, David Hildenbrand <david@...hat.com>, Rex Nie
	<rex.nie@...uarmicro.com>, Dave Martin <dave.martin@....com>, Koba Ko
	<kobak@...dia.com>
Subject: Re: [RFC PATCH 20/36] arm_mpam: Probe the hardware features resctrl
 supports

}
> >   
> > +/*
> > + * IHI009A.a has this nugget: "If a monitor does not support automatic behaviour
> > + * of NRDY, software can use this bit for any purpose" - so hardware might not
> > + * implement this - but it isn't RES0.
> > + *
> > + * Try and see what values stick in this bit. If we can write either value,
> > + * its probably not implemented by hardware.
> > + */
> > +#define mpam_ris_hw_probe_hw_nrdy(_ris, _mon_reg, _result)			\
> > +do {										\
> > +	u32 now;								\
> > +	u64 mon_sel;								\
> > +	bool can_set, can_clear;						\
> > +	struct mpam_msc *_msc = _ris->vmsc->msc;				\
> > +										\
> > +	if (WARN_ON_ONCE(!mpam_mon_sel_inner_lock(_msc))) {			\
> > +		_result = false;						\
> > +		break;								\
> > +	}									\
> > +	mon_sel = FIELD_PREP(MSMON_CFG_MON_SEL_MON_SEL, 0) |			\
> > +		  FIELD_PREP(MSMON_CFG_MON_SEL_RIS, _ris->ris_idx);		\
> > +	mpam_write_monsel_reg(_msc, CFG_MON_SEL, mon_sel);			\
> > +										\
> > +	mpam_write_monsel_reg(_msc, _mon_reg, MSMON___NRDY);			\
> > +	now = mpam_read_monsel_reg(_msc, _mon_reg);				\
> > +	can_set = now & MSMON___NRDY;						\
> > +										\
> > +	mpam_write_monsel_reg(_msc, _mon_reg, 0);				\
> > +	now = mpam_read_monsel_reg(_msc, _mon_reg);				\
> > +	can_clear = !(now & MSMON___NRDY);					\
> > +	mpam_mon_sel_inner_unlock(_msc);					\
> > +										\
> > +	_result = (!can_set || !can_clear);					\
> > +} while (0)  
> It is a bit surprising that something that looks like a function 
> modifies a boolean passed by value. Consider continuing the pattern you 
> have above:
> #define mpam_ris_hw_probe_hw_nrdy(_ris, _mon_reg, _result) 
> _mpam_ris_hw_probe_hw_nrdy(_ris, MSMON##_mon_reg, _result)
> 
> with signature:
> void _mpam_ris_hw_probe_hw_nrdy(struct mpam_msc *msc, u16 reg, bool 
> *hw_managed);
> 
> and using the _mpam functions from the new _mpam_ris_hw_probe_hw_nrdy().
> 

Agreed that this is ugly.  Only a tiny bit of macro stuff is actually going on here.
I'd make it function.

If you really want to construct MSMON_CSU etc then wrap that helper with
a macro that builds reg from the name.

I might have missed something though in converting this.
The version I have has some other changes though so not trivial to post here :(