linux-kernel - Re: [PATCH 1/1] virt/kvm/iommu.c: Add leading zeros to device's BDF notation in debug messages

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Date:	Wed, 2 Oct 2013 21:08:13 +0200
From:	Andre Richter <andre.o.richter@...il.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	Gleb Natapov <gleb@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] virt/kvm/iommu.c: Add leading zeros to device's BDF
 notation in debug messages

2013/10/2 Alex Williamson <alex.williamson@...hat.com>:
> On Wed, 2013-10-02 at 13:35 +0300, Gleb Natapov wrote:
>> On Wed, Oct 02, 2013 at 12:23:26PM +0200, Andre Richter wrote:
>> > When KVM (de)assigns PCI(e) devices to VMs, a debug message is printed
>> > including the BDF notation of the respective device. Currently, the BDF
>> > notation does not have the commonly used leading zeros. This produces
>> > messages like "assign device 0:1:8.0", which look strange at first sight.
>> >
>> > The patch fixes this by exchanging the printk(KERN_DEBUG ...) with dev_info()
>> > and also inserts "kvm" into the debug message, so that it is obvious where
>> > the message comes from. Also reduces LoC.
>> Legacy assigned device is deprecated, but this looks nice enough to
>> apply. Alex can you glance at it?
>
> Seems ok to me, my only question would be why are we promoting this from
> KERN_DEBUG to KERN_INFO.  We could use dev_dbg() to maintain the same
> kernel log level.  A nice feature of either is that it prints out the
> attached driver so we can see in dmesg whether the device is attached to
> a host driver, nothing, or pci-stub.  Thanks,
>
> Alex

I made it dev_info() because on my test system, dev_dbg() did not show
up in dmesg, whereas
the original printk(KERN_DEBUG ...) did. I guess dev_dbg() was
stripped due to compiling without DEBUG?
Therefore, I found dev_info() to better mimic the original behavior. I
can change it to dev_dbg() if you wish?

Andre

>
>> >
>> > Signed-off-by: Andre Richter <andre.o.richter@...il.com>
>> > ---
>> >  virt/kvm/iommu.c | 12 ++----------
>> >  1 file changed, 2 insertions(+), 10 deletions(-)
>> >
>> > diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
>> > index 72a130b..a3b1410 100644
>> > --- a/virt/kvm/iommu.c
>> > +++ b/virt/kvm/iommu.c
>> > @@ -190,11 +190,7 @@ int kvm_assign_device(struct kvm *kvm,
>> >
>> >     pdev->dev_flags |= PCI_DEV_FLAGS_ASSIGNED;
>> >
>> > -   printk(KERN_DEBUG "assign device %x:%x:%x.%x\n",
>> > -           assigned_dev->host_segnr,
>> > -           assigned_dev->host_busnr,
>> > -           PCI_SLOT(assigned_dev->host_devfn),
>> > -           PCI_FUNC(assigned_dev->host_devfn));
>> > +   dev_info(&pdev->dev, "kvm assign device\n");
>> >
>> >     return 0;
>> >  out_unmap:
>> > @@ -220,11 +216,7 @@ int kvm_deassign_device(struct kvm *kvm,
>> >
>> >     pdev->dev_flags &= ~PCI_DEV_FLAGS_ASSIGNED;
>> >
>> > -   printk(KERN_DEBUG "deassign device %x:%x:%x.%x\n",
>> > -           assigned_dev->host_segnr,
>> > -           assigned_dev->host_busnr,
>> > -           PCI_SLOT(assigned_dev->host_devfn),
>> > -           PCI_FUNC(assigned_dev->host_devfn));
>> > +   dev_info(&pdev->dev, "kvm deassign device\n");
>> >
>> >     return 0;
>> >  }
>> > --
>> > 1.8.1.2
>>
>> --
>>                       Gleb.
>
>
>
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