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From: Lukas Wunner <lukas@wunner.de>
To: Kelsey Skunberg <skunberg.kelsey@gmail.com>
Cc: bhelgaas@google.com, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-kernel-mentees@lists.linuxfoundation.org,
	skhan@linuxfoundation.org, rafael.j.wysocki@intel.com,
	keith.busch@intel.com
Subject: Re: [PATCH 2/2] PCI: Unify pci_dev_is_disconnected() and pci_dev_is_inaccessible()
Date: Wed, 4 Sep 2019 07:35:23 +0200	[thread overview]
Message-ID: <20190904053523.7lmuoo5zempxtsdq@wunner.de> (raw)
In-Reply-To: <20190904043633.65026-3-skunberg.kelsey@gmail.com>

On Tue, Sep 03, 2019 at 10:36:35PM -0600, Kelsey Skunberg wrote:
> Change pci_dev_is_disconnected() call inside pci_dev_is_inaccessible() to:
> 
> 	pdev->error_state == pci_channel_io_perm_failure
> 
> Change remaining pci_dev_is_disconnected() calls to
> pci_dev_is_inaccessible() calls.

I don't think that's a good idea because it introduces a config space read
(for the vendor ID) in places where we don't want that.  E.g., after the
check of pdev->error_state, a regular config space read may take place and
if that returns all ones, we may already be able to determine that the
device is inaccessible, obviating the need for a vendor ID check.
Config space reads aren't for free.

Thanks,

Lukas

  reply	other threads:[~2019-09-04  5:35 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-04  4:36 [PATCH 0/2] PCI: Change to using pci_dev_is_inaccessible() Kelsey Skunberg
2019-09-04  4:36 ` [PATCH 1/2] PCI: Change pci_device_is_present() to pci_dev_is_inaccessible() Kelsey Skunberg
2019-09-04  4:36 ` [PATCH 2/2] PCI: Unify pci_dev_is_disconnected() and pci_dev_is_inaccessible() Kelsey Skunberg
2019-09-04  5:35   ` Lukas Wunner [this message]
2019-09-04 18:45     ` Bjorn Helgaas
2019-09-05  6:43     ` Kelsey Skunberg

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