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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Christoph Hellwig <hch@lst.de>
Cc: sagi@grimberg.me, linux-nvme@lists.infradead.org,
	ming.lei@redhat.com, helgaas@kernel.org,
	Keith Busch <kbusch@kernel.org>,
	tglx@linutronix.de
Subject: Re: [PATCHv2 1/2] PCI/MSI: Export __pci_msix_desc_mask_irq
Date: Tue, 3 Dec 2019 10:04:54 +0100
Message-ID: <20191203090454.ftfu6pyz2ubxg7fk@linutronix.de> (raw)
In-Reply-To: <20191202224603.GA14770@lst.de>

On 2019-12-02 23:46:03 [+0100], Christoph Hellwig wrote:
> On Tue, Dec 03, 2019 at 07:20:57AM +0900, Keith Busch wrote:
> > Export the fast msix mask for drivers to use when the read-back is
> > undesired.
> 
> As said last time calling this seems wrong as it breaks the irq_chip
> abstraction.  But looking at the disable_irq_nosync semantics I think
> that function should do a non-pasted disable disable for MSI(-X)
> interrupts.  Can you look into that?

Using disable_irq_nosync() would be the same as using IRQF_ONESHOT which
is the preferred way.
Keith complained about this as slow and avoiding the read-back as
noticeable.

The generic way would be pci_msi_mask_irq() and the difference

|                 msix_mask_irq(desc, flag);
|                 readl(desc->mask_base);         /* Flush write to device */

would be that flush.

Sebastian

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Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-02 22:20 [PATCHv2 0/2] Keith Busch
2019-12-02 22:20 ` [PATCHv2 1/2] PCI/MSI: Export __pci_msix_desc_mask_irq Keith Busch
2019-12-02 22:46   ` Christoph Hellwig
2019-12-03  9:04     ` Sebastian Andrzej Siewior [this message]
2019-12-02 22:20 ` [PATCHv2 2/2] nvme/pci: Mask device interrupts for threaded handlers Keith Busch
2019-12-03  7:47   ` Christoph Hellwig
2019-12-03 12:07     ` Keith Busch
2019-12-04 10:10   ` Sironi, Filippo
2019-12-04 13:58     ` hch

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