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From: Thomas Gleixner <tglx@linutronix.de>
To: "Jürgen Groß" <jgross@suse.com>,
	boris.ostrovsky@oracle.com, LKML <linux-kernel@vger.kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Karthikeyan Mitran <m.karthikeyan@mobiveil.co.in>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	dri-devel@lists.freedesktop.org,
	Chris Wilson <chris@chris-wilson.co.uk>,
	"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
	Saeed Mahameed <saeedm@nvidia.com>,
	netdev@vger.kernel.org, Jakub Kicinski <kuba@kernel.org>,
	Will Deacon <will@kernel.org>,
	Michal Simek <michal.simek@xilinx.com>,
	linux-s390@vger.kernel.org,
	afzal mohammed <afzal.mohd.ma@gmail.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Dave Jiang <dave.jiang@intel.com>,
	Leon Romanovsky <leon@kernel.org>,
	linux-rdma@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	Helge Deller <deller@gmx.de>,
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	Christian Borntraeger <borntraeger@de.ibm.com>,
	linux-pci@vger.kernel.org, xen-devel@lists.xenproject.org,
	Heiko Carstens <hca@linux.ibm.com>,
	Wambui Karuga <wambui.karugax@gmail.com>,
	Allen Hubbe <allenbh@gmail.com>, David Airlie <airlied@linux.ie>,
	linux-gpio@vger.kernel.org,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
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	Bjorn Helgaas <bhelgaas@google.com>,
	Lee Jones <lee.jones@linaro.org>,
	linux-arm-kernel@lists.infradead.org,
	Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
	linux-parisc@vger.kernel.org,
	Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@intel.com>,
	Hou Zhiqiang <Zhiqiang.Hou@nxp.com>,
	Tariq Toukan <tariqt@nvidia.com>, Jon Mason <jdmason@kudzu.us>,
	linux-ntb@googlegroups.com, intel-gfx@lists.freedesktop.org,
	"David S. Miller" <davem@davemloft.net>
Subject: Re: [patch 27/30] xen/events: Only force affinity mask for percpu interrupts
Date: Fri, 11 Dec 2020 13:37:10 +0100
Message-ID: <871rfwiknd.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <2164a0ce-0e0d-c7dc-ac97-87c8f384ad82@suse.com>

On Fri, Dec 11 2020 at 13:10, Jürgen Groß wrote:
> On 11.12.20 00:20, boris.ostrovsky@oracle.com wrote:
>> 
>> On 12/10/20 2:26 PM, Thomas Gleixner wrote:
>>> All event channel setups bind the interrupt on CPU0 or the target CPU for
>>> percpu interrupts and overwrite the affinity mask with the corresponding
>>> cpumask. That does not make sense.
>>>
>>> The XEN implementation of irqchip::irq_set_affinity() already picks a
>>> single target CPU out of the affinity mask and the actual target is stored
>>> in the effective CPU mask, so destroying the user chosen affinity mask
>>> which might contain more than one CPU is wrong.
>>>
>>> Change the implementation so that the channel is bound to CPU0 at the XEN
>>> level and leave the affinity mask alone. At startup of the interrupt
>>> affinity will be assigned out of the affinity mask and the XEN binding will
>>> be updated.
>> 
>> 
>> If that's the case then I wonder whether we need this call at all and instead bind at startup time.
>
> After some discussion with Thomas on IRC and xen-devel archaeology the
> result is: this will be needed especially for systems running on a
> single vcpu (e.g. small guests), as the .irq_set_affinity() callback
> won't be called in this case when starting the irq.

That's right, but not limited to ARM. The same problem exists on x86 UP.
So yes, the call makes sense, but the changelog is not really useful.
Let me add a comment to this.

Thanks,

        tglx
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Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-10 19:25 [patch 00/30] genirq: Treewide hunt for irq descriptor abuse and assorted fixes Thomas Gleixner
2020-12-10 19:25 ` [patch 01/30] genirq: Move irq_has_action() into core code Thomas Gleixner
2020-12-10 19:25 ` [patch 02/30] genirq: Move status flag checks to core Thomas Gleixner
2020-12-27 19:20   ` Guenter Roeck
2021-01-11 10:14     ` Thomas Gleixner
2020-12-10 19:25 ` [patch 03/30] genirq: Move irq_set_lockdep_class() " Thomas Gleixner
2020-12-11 17:53   ` Andy Shevchenko
2020-12-11 21:08     ` Thomas Gleixner
2020-12-11 22:07       ` Thomas Gleixner
2020-12-12 13:22         ` Andy Shevchenko
2020-12-10 19:25 ` [patch 04/30] genirq: Provide irq_get_effective_affinity() Thomas Gleixner
2020-12-10 19:25 ` [patch 05/30] genirq: Annotate irq stats data races Thomas Gleixner
2020-12-10 19:25 ` [patch 06/30] parisc/irq: Simplify irq count output for /proc/interrupts Thomas Gleixner
2020-12-10 19:25 ` [patch 07/30] genirq: Make kstat_irqs() static Thomas Gleixner
2020-12-10 19:25 ` [patch 08/30] genirq: Provide kstat_irqdesc_cpu() Thomas Gleixner
2020-12-10 19:25 ` [patch 09/30] ARM: smp: Use irq_desc_kstat_cpu() in show_ipi_list() Thomas Gleixner
2020-12-11 18:08   ` Marc Zyngier
2020-12-10 19:25 ` [patch 10/30] arm64/smp: Use irq_desc_kstat_cpu() in arch_show_interrupts() Thomas Gleixner
2020-12-11 18:08   ` Marc Zyngier
2020-12-10 19:25 ` [patch 11/30] parisc/irq: Use irq_desc_kstat_cpu() in show_interrupts() Thomas Gleixner
2020-12-10 19:25 ` [patch 12/30] s390/irq: Use irq_desc_kstat_cpu() in show_msi_interrupt() Thomas Gleixner
2020-12-10 20:31   ` Heiko Carstens
2020-12-10 19:25 ` [patch 13/30] drm/i915/lpe_audio: Remove pointless irq_to_desc() usage Thomas Gleixner
2020-12-10 19:48   ` [Intel-gfx] " Ville Syrjälä
2020-12-11  9:51     ` Jani Nikula
2020-12-10 19:25 ` [patch 14/30] drm/i915/pmu: Replace open coded kstat_irqs() copy Thomas Gleixner
2020-12-11  9:54   ` Jani Nikula
2020-12-11 10:13   ` Tvrtko Ursulin
2020-12-11 12:57     ` Thomas Gleixner
2020-12-11 14:19       ` David Laight
2020-12-11 21:10         ` Thomas Gleixner
2020-12-11 22:06           ` David Laight
2020-12-10 19:25 ` [patch 15/30] pinctrl: nomadik: Use irq_has_action() Thomas Gleixner
2020-12-12  0:45   ` Linus Walleij
2020-12-10 19:25 ` [patch 16/30] mfd: ab8500-debugfs: Remove the racy fiddling with irq_desc Thomas Gleixner
2020-12-11  8:22   ` Linus Walleij
2020-12-11 10:04   ` Lee Jones
2020-12-11 18:12   ` Andy Shevchenko
2020-12-10 19:25 ` [patch 17/30] NTB/msi: Use irq_has_action() Thomas Gleixner
2020-12-10 20:33   ` Logan Gunthorpe
2020-12-10 19:25 ` [patch 18/30] PCI: xilinx-nwl: Use irq_data_get_irq_chip_data() Thomas Gleixner
2020-12-10 22:56   ` Rob Herring
2020-12-10 19:25 ` [patch 19/30] PCI: mobiveil: " Thomas Gleixner
2020-12-10 22:56   ` Rob Herring
2020-12-10 19:25 ` [patch 20/30] net/mlx4: Replace irq_to_desc() abuse Thomas Gleixner
2020-12-13 11:24   ` Tariq Toukan
2020-12-10 19:25 ` [patch 21/30] net/mlx4: Use effective interrupt affinity Thomas Gleixner
2020-12-13 11:31   ` Tariq Toukan
2020-12-10 19:25 ` [patch 22/30] net/mlx5: Replace irq_to_desc() abuse Thomas Gleixner
2020-12-13 11:34   ` Tariq Toukan
2020-12-14 21:13   ` Saeed Mahameed
2020-12-10 19:25 ` [patch 23/30] net/mlx5: Use effective interrupt affinity Thomas Gleixner
2020-12-13 11:35   ` Tariq Toukan
2020-12-14 20:58   ` Saeed Mahameed
2020-12-10 19:26 ` [patch 24/30] xen/events: Remove unused bind_evtchn_to_irq_lateeoi() Thomas Gleixner
2020-12-10 23:19   ` boris.ostrovsky
2020-12-11  0:04     ` Thomas Gleixner
2020-12-10 19:26 ` [patch 25/30] xen/events: Remove disfunct affinity spreading Thomas Gleixner
2020-12-10 19:26 ` [patch 26/30] xen/events: Use immediate affinity setting Thomas Gleixner
2020-12-10 19:26 ` [patch 27/30] xen/events: Only force affinity mask for percpu interrupts Thomas Gleixner
2020-12-10 23:20   ` boris.ostrovsky
2020-12-11  0:06     ` Thomas Gleixner
2020-12-11  6:17     ` Jürgen Groß
     [not found]       ` <874kksiras.fsf@nanos.tec.linutronix.de>
2020-12-11 10:23         ` Jürgen Groß
2020-12-11 12:10     ` Jürgen Groß
2020-12-11 12:37       ` Thomas Gleixner [this message]
2020-12-11 14:29         ` boris.ostrovsky
2020-12-11 21:27           ` Thomas Gleixner
2020-12-11 22:21             ` Andrew Cooper
2020-12-11 22:56               ` Thomas Gleixner
2020-12-10 19:26 ` [patch 28/30] xen/events: Reduce irq_info::spurious_cnt storage size Thomas Gleixner
2020-12-10 19:26 ` [patch 29/30] xen/events: Implement irq distribution Thomas Gleixner
2020-12-10 19:26 ` [patch 30/30] genirq: Remove export of irq_to_desc() Thomas Gleixner

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