From: "Jürgen Groß" <jgross@suse.com>
To: Thomas Gleixner <tglx@linutronix.de>,
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>,
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Stefano Stabellini <sstabellini@kernel.org>,
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"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 11:23:13 +0100 [thread overview]
Message-ID: <83b596c7-453b-34b5-a6a5-6c04d20e818a@suse.com> (raw)
In-Reply-To: <874kksiras.fsf@nanos.tec.linutronix.de>
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On 11.12.20 11:13, Thomas Gleixner wrote:
> On Fri, Dec 11 2020 at 07:17, 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.
>>
>> This binding to cpu0 was introduced with commit 97253eeeb792d61ed2
>> and I have no reason to believe the underlying problem has been
>> eliminated.
>
> "The kernel-side VCPU binding was not being correctly set for newly
> allocated or bound interdomain events. In ARM guests where 2-level
> events were used, this would result in no interdomain events being
> handled because the kernel-side VCPU masks would all be clear.
>
> x86 guests would work because the irq affinity was set during irq
> setup and this would set the correct kernel-side VCPU binding."
>
> I'm not convinced that this is really correctly analyzed because affinity
> setting is done at irq startup.
>
> switch (__irq_startup_managed(desc, aff, force)) {
> case IRQ_STARTUP_NORMAL:
> ret = __irq_startup(desc);
> irq_setup_affinity(desc);
> break;
>
> which is completely architecture agnostic. So why should this magically
> work on x86 and not on ARM if both are using the same XEN irqchip with
> the same irqchip callbacks.
I think this might be related to _initial_ cpu binding of events and
changing the binding later. This might be handled differently in the
hypervisor.
Juergen
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next prev parent reply other threads:[~2020-12-11 10:23 UTC|newest]
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 [this message]
2020-12-11 12:10 ` Jürgen Groß
2020-12-11 12:37 ` Thomas Gleixner
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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