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From: Ming Lei <ming.lei@redhat.com>
To: John Garry <john.garry@huawei.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	linux-pci@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
	Sagi Grimberg <sagi@grimberg.me>, Daniel Wagner <dwagner@suse.de>,
	Wen Xiong <wenxiong@us.ibm.com>, Hannes Reinecke <hare@suse.de>,
	Keith Busch <kbusch@kernel.org>
Subject: Re: [PATCH V4 1/3] driver core: mark device as irq affinity managed if any irq is managed
Date: Tue, 20 Jul 2021 10:38:08 +0800	[thread overview]
Message-ID: <YPY3EMngyf2JFZ3j@T590> (raw)
In-Reply-To: <5153406c-e3ed-d466-5603-14fd919304f4@huawei.com>

On Mon, Jul 19, 2021 at 11:39:53AM +0100, John Garry wrote:
> On 19/07/2021 10:44, Christoph Hellwig wrote:
> > On Mon, Jul 19, 2021 at 08:51:22AM +0100, John Garry wrote:
> > > > Address this issue by adding one field of .irq_affinity_managed into
> > > > 'struct device'.
> > > > 
> > > > Suggested-by: Christoph Hellwig <hch@lst.de>
> > > > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > > 
> > > Did you consider that for PCI device we effectively have this info already:
> > > 
> > > bool dev_has_managed_msi_irq(struct device *dev)
> > > {
> > > 	struct msi_desc *desc;
> > > 
> > > 	list_for_each_entry(desc, dev_to_msi_list(dev), list)
> 
> I just noticed for_each_msi_entry(), which is the same
> 
> 
> > > 		if (desc->affinity && desc->affinity->is_managed)
> > > 			return true;
> > > 	}
> > > 
> > > 	return false;
> > 
> > Just walking the list seems fine to me given that this is not a
> > performance criticial path.  But what are the locking implications?
> 
> Since it would be used for sequential setup code, I didn't think any locking
> was required. But would need to consider where that function lived and
> whether it's public.

Yeah, the allocated irq vectors should be live when running map queues.

> 
> > 
> > Also does the above imply this won't work for your platform MSI case?
> > .
> > 
> 
> Right. I think that it may be possible to reach into the platform msi
> descriptors to get this info, but I am not sure it's worth it. There is only
> 1x user there and there is no generic .map_queues function, so could set the
> flag directly:
> 
> int blk_mq_pci_map_queues(struct blk_mq_queue_map *qmap, struct pci_dev
> *pdev,
>  		for_each_cpu(cpu, mask)
>  			qmap->mq_map[cpu] = qmap->queue_offset + queue;
>  	}
> +	qmap->use_managed_irq = dev_has_managed_msi_irq(&pdev->dev);
> }
> 
> --- a/drivers/scsi/hisi_sas/hisi_sas_v2_hw.c
> +++ b/drivers/scsi/hisi_sas/hisi_sas_v2_hw.c
> @@ -3563,6 +3563,8 @@ static int map_queues_v2_hw(struct Scsi_Host *shost)
>                        qmap->mq_map[cpu] = qmap->queue_offset + queue;
>        }
> 
> +       qmap->use_managed_irq = 1;
> +
>        return 0;

virtio can be populated via platform device too, but managed irq affinity
isn't used, so seems dev_has_managed_msi_irq() is fine.


Thanks,
Ming


  reply	other threads:[~2021-07-20  2:48 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-15 12:08 [PATCH V4 0/3] blk-mq: fix blk_mq_alloc_request_hctx Ming Lei
2021-07-15 12:08 ` [PATCH V4 1/3] driver core: mark device as irq affinity managed if any irq is managed Ming Lei
2021-07-15 12:40   ` Greg Kroah-Hartman
2021-07-16  2:17     ` Ming Lei
2021-07-16 20:01   ` Bjorn Helgaas
2021-07-17  9:30     ` Ming Lei
2021-07-21  0:30       ` Bjorn Helgaas
2021-07-19  7:51   ` John Garry
2021-07-19  9:44     ` Christoph Hellwig
2021-07-19 10:39       ` John Garry
2021-07-20  2:38         ` Ming Lei [this message]
2021-07-21  7:20       ` Thomas Gleixner
2021-07-21  7:24         ` Christoph Hellwig
2021-07-21  9:44           ` John Garry
2021-07-21 20:22             ` Thomas Gleixner
2021-07-22  7:48               ` John Garry
2021-07-21 20:14           ` Thomas Gleixner
2021-07-21 20:32             ` Christoph Hellwig
2021-07-21 22:38               ` Thomas Gleixner
2021-07-22  7:46                 ` Christoph Hellwig
2021-07-15 12:08 ` [PATCH V4 2/3] blk-mq: mark if one queue map uses managed irq Ming Lei
2021-07-15 12:08 ` [PATCH V4 3/3] blk-mq: don't deactivate hctx if managed irq isn't used Ming Lei

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