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[2003:ea:8bd4:d600:9545:19fe:eae2:90aa]) by smtp.googlemail.com with ESMTPSA id v10-v6sm3346332wrm.18.2018.08.03.13.55.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 03 Aug 2018 13:55:05 -0700 (PDT) Subject: Re: [PATCH] PCI: let pci_request_irq properly deal with threaded interrupts To: Thomas Gleixner Cc: Marc Zyngier , Bjorn Helgaas , Bjorn Helgaas , linux-pci@vger.kernel.org, Christoph Hellwig , LKML References: <20180730213028.GC45322@bhelgaas-glaptop.roam.corp.google.com> <86d0v4x75x.wl-marc.zyngier@arm.com> <0799ea22-70ed-3be6-cb80-449f53fef819@gmail.com> <420d6476-8ea4-0b37-e94a-f5842b7b0ff7@gmail.com> From: Heiner Kallweit Message-ID: <96285966-f2d2-c820-7f38-de22deeb8074@gmail.com> Date: Fri, 3 Aug 2018 22:55:00 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03.08.2018 21:40, Thomas Gleixner wrote: > On Fri, 3 Aug 2018, Heiner Kallweit wrote: >> On 03.08.2018 16:09, Thomas Gleixner wrote: >>> On Wed, 1 Aug 2018, Heiner Kallweit wrote: >>>> diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c >>>> index 4ca2fd46..ba6da943 100644 >>>> --- a/kernel/irq/msi.c >>>> +++ b/kernel/irq/msi.c >>>> @@ -289,6 +289,9 @@ struct irq_domain *msi_create_irq_domain(struct fwnode_handle *fwnode, >>>> if (info->flags & MSI_FLAG_USE_DEF_CHIP_OPS) >>>> msi_domain_update_chip_ops(info); >>>> >>>> + /* MSI is oneshot-safe in general */ >>>> + info->chip->flags |= IRQCHIP_ONESHOT_SAFE; >>>> + >>>> domain = irq_domain_create_hierarchy(parent, IRQ_DOMAIN_FLAG_MSI, 0, >>> >>> Looks about right, though there might be dragons. MSI is not always as sane >>> as it should be... >>> >> When saying "MSI isn't always sane", are you referring to the hardware or >> the controller driver implementation? Basically for me the question is >> whether we would be able to fix the issue if we meet such a dragon, >> or whether we would have to revert the change. > > It's hardware unfortunately, so it might be a revert. PCI-MSI should be > safe, but the wild MSI variants in SoCs might be the actual dragon caves. > pci_msi_create_irq_domain() is used by controller drivers for PCI(e) controllers in SoCs like Mediatek, Armada, .. I assume you're referring to some other (non-PCI) SoC-internal MSI mechanism when saying "wild variants", right? >> Do you think the chance of a dragon is low enough? Or better add the >> flag only to the X86 PCI MSI irqchip for now? > > I think PCI-MSI in general would be not too risky. Famous last words. > > Thanks, > > tglx >