linux-kernel - Re: [PATCH v6] numa: make node_to_cpumask_map() NUMA_NO

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Message-ID: <20191012074014.GA2037204@kroah.com>
Date:   Sat, 12 Oct 2019 09:40:14 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Yunsheng Lin <linyunsheng@...wei.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Michal Hocko <mhocko@...nel.org>,
        Robin Murphy <robin.murphy@....com>, catalin.marinas@....com,
        will@...nel.org, mingo@...hat.com, bp@...en8.de, rth@...ddle.net,
        ink@...assic.park.msu.ru, mattst88@...il.com,
        benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        heiko.carstens@...ibm.com, gor@...ux.ibm.com,
        borntraeger@...ibm.com, ysato@...rs.sourceforge.jp,
        dalias@...c.org, davem@...emloft.net, ralf@...ux-mips.org,
        paul.burton@...s.com, jhogan@...nel.org, jiaxun.yang@...goat.com,
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        anshuman.khandual@....com, tglx@...utronix.de, cai@....pw,
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        hpa@...or.com, x86@...nel.org, dave.hansen@...ux.intel.com,
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        dledford@...hat.com, jeffrey.t.kirsher@...el.com,
        linux-alpha@...r.kernel.org, naveen.n.rao@...ux.vnet.ibm.com,
        mwb@...ux.vnet.ibm.com, linuxppc-dev@...ts.ozlabs.org,
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        sparclinux@...r.kernel.org, tbogendoerfer@...e.de,
        linux-mips@...r.kernel.org, rafael@...nel.org, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
        lenb@...nel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v6] numa: make node_to_cpumask_map() NUMA_NO_NODE aware

On Sat, Oct 12, 2019 at 02:17:26PM +0800, Yunsheng Lin wrote:
> add pci and acpi maintainer
> cc linux-pci@...r.kernel.org and linux-acpi@...r.kernel.org
> 
> On 2019/10/11 19:15, Peter Zijlstra wrote:
> > On Fri, Oct 11, 2019 at 11:27:54AM +0800, Yunsheng Lin wrote:
> >> But I failed to see why the above is related to making node_to_cpumask_map()
> >> NUMA_NO_NODE aware?
> > 
> > Your initial bug is for hns3, which is a PCI device, which really _MUST_
> > have a node assigned.
> > 
> > It not having one, is a straight up bug. We must not silently accept
> > NO_NODE there, ever.
> > 
> 
> I suppose you mean reporting a lack of affinity when the node of a pcie
> device is not set by "not silently accept NO_NODE".

If the firmware of a pci device does not provide the node information,
then yes, warn about that.

> As Greg has asked about in [1]:
> what is a user to do when the user sees the kernel reporting that?
> 
> We may tell user to contact their vendor for info or updates about
> that when they do not know about their system well enough, but their
> vendor may get away with this by quoting ACPI spec as the spec
> considering this optional. Should the user believe this is indeed a
> fw bug or a misreport from the kernel?

Say it is a firmware bug, if it is a firmware bug, that's simple.

> If this kind of reporting is common pratice and will not cause any
> misunderstanding, then maybe we can report that.

Yes, please do so, that's the only way those boxes are ever going to get
fixed.  And go add the test to the "firmware testing" tool that is based
on Linux that Intel has somewhere, to give vendors a chance to fix this
before they ship hardware.

This shouldn't be a big deal, we warn of other hardware bugs all the
time.

thanks,

greg k-h