linux-kernel - Re: [PATCH v8 1/2] arm: introduce psci_smp

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: <alpine.DEB.2.02.1304251158080.4180@kaball.uk.xensource.com>
Date:	Thu, 25 Apr 2013 12:08:02 +0100
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Will Deacon <will.deacon@....com>
CC:	Stefano Stabellini <Stefano.Stabellini@...citrix.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"arnd@...db.de" <arnd@...db.de>,
	"nicolas.pitre@...aro.org" <nicolas.pitre@...aro.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"olof@...om.net" <olof@...om.net>
Subject: Re: [PATCH v8 1/2] arm: introduce psci_smp_ops

On Thu, 25 Apr 2013, Will Deacon wrote:
> On Thu, Apr 25, 2013 at 11:12:54AM +0100, Stefano Stabellini wrote:
> > On Thu, 25 Apr 2013, Will Deacon wrote:
> > > > +/*
> > > > + * cpu_suspend   Suspend the execution on a CPU
> > > > + * @state        we don't currently describe affinity levels, so just pass 0.
> > > > + * @entry_point  the first instruction to be executed on return
> > > > + * returns 0  success, < 0 on failure
> > > > + *
> > > > + * cpu_off       Power down a CPU
> > > > + * @state        we don't currently describe affinity levels, so just pass 0.
> > > > + * no return on successful call
> > > > + *
> > > > + * cpu_on        Power up a CPU
> > > > + * @cpuid        cpuid of target CPU, as from MPIDR
> > > > + * @entry_point  the first instruction to be executed on return
> > > > + * returns 0  success, < 0 on failure
> > > > + *
> > > > + * migrate       Migrate the context to a different CPU
> > > > + * @cpuid        cpuid of target CPU, as from MPIDR
> > > > + * returns 0  success, < 0 on failure
> > > > + *
> > > > + */
> > > 
> > > Can you move these comments into psci-smp.c please? They're really specific
> > > to the implementation there, and if we put them in a header we're lying to
> > > ourselves about the parameters actually described by the PSCI specification.
> > 
> > You have a good point about the PSCI spec.
> > 
> > However from the Linux POV these comments should regard the functions
> > exported by psci_operations, not the firmware interface, this is why I
> > think it makes sense to keep them in psci.h.
> > What we are saying is for example that psci_operations.cpu_on returns 0
> > on success and < 0 on failure, and it takes a cpuid and an entry point
> > as parameters. We are not saying anything about the firmware interface.
> 
> I disagree. You're explicitly stating that we pass the `cpuid of target CPU,
> as from MPIDR'. That's simply not true -- the firmware could choose any
> numbering scheme to identify the CPUs. For KVM and Xen, it *is* the mpidr,
> which is why psci-smp.c works at all, but that's where the comment belongs,
> not in this header file.

I see, you want to keep psci_operations true to the firmware interface
while explaining that psci_smp makes some assumptions about it.
So the comment should be something like:

/*
 * psci_smp assumes that the following is true about PSCI:
 * 
 * cpu_suspend   Suspend the execution on a CPU
 * @state        we don't currently describe affinity levels, so just pass 0.
 * @entry_point  the first instruction to be executed on return
 * returns 0  success, < 0 on failure
 *
 * cpu_off       Power down a CPU
 * @state        we don't currently describe affinity levels, so just pass 0.
 * no return on successful call
 *
 * cpu_on        Power up a CPU
 * @cpuid        cpuid of target CPU, as from MPIDR
 * @entry_point  the first instruction to be executed on return
 * returns 0  success, < 0 on failure
 *
 * migrate       Migrate the context to a different CPU
 * @cpuid        cpuid of target CPU, as from MPIDR
 * returns 0  success, < 0 on failure
 *
 */
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/