netdev - Re: [RFC net-next PATCH 1/4] pci: Add flag indicating device has been assigned by KVM

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Date:	Thu, 28 Jul 2011 16:11:17 +0100
From:	Ian Campbell <ijc@...lion.org.uk>
To:	Greg Rose <gregory.v.rose@...el.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net,
	bhutchings@...arflare.com, jeffrey.t.kirsher@...el.com,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	linux-pci@...r.kernel.org
Subject: Re: [RFC net-next PATCH 1/4] pci: Add flag indicating device has
 been assigned by KVM

On Wed, 2011-07-27 at 15:17 -0700, Greg Rose wrote:
> Device drivers that create and destroy SR-IOV virtual functions via
> calls to pci_enable_sriov() and pci_disable_sriov can cause catastrophic
> failures if they attempt to destroy VFs while they are assigned to
> guest virtual machines.  By adding a flag for use by the KVM module
> to indicate that a device is assigned a device driver can check that
> flag and avoid destroying VFs while they are assigned and avoid system
> failures.
> 
> Signed-off-by: Greg Rose <gregory.v.rose@...el.com>
> ---
> 
>  include/linux/pci.h     |    2 ++

I added Jesse and linux-pci to CC.

>  virt/kvm/assigned-dev.c |    2 ++
>  virt/kvm/iommu.c        |    4 ++++
>  3 files changed, 8 insertions(+), 0 deletions(-)

I suppose this would also be useful in Xen's pciback or any other system
which does passthrough? (Konrad CC'd for pciback)

Is there some common lower layer we could hook this in to? (does
iommu_attach/detach_device make sense?) Or shall we just add the flag
manipulations to pciback as well?

Ian.

> 
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 2d29218..a297ca2 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -174,6 +174,8 @@ enum pci_dev_flags {
>  	PCI_DEV_FLAGS_MSI_INTX_DISABLE_BUG = (__force pci_dev_flags_t) 1,
>  	/* Device configuration is irrevocably lost if disabled into D3 */
>  	PCI_DEV_FLAGS_NO_D3 = (__force pci_dev_flags_t) 2,
> +	/* Provide indication device is assigned by KVM */
> +	PCI_DEV_FLAGS_ASSIGNED = (__force pci_dev_flags_t) 4,
>  };
>  
>  enum pci_irq_reroute_variant {
> diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
> index 6cc4b97..f401de1 100644
> --- a/virt/kvm/assigned-dev.c
> +++ b/virt/kvm/assigned-dev.c
> @@ -205,6 +205,8 @@ static void kvm_free_assigned_device(struct kvm *kvm,
>  	else
>  		pci_restore_state(assigned_dev->dev);
>  
> +	assigned_dev->dev->dev_flags &= ~PCI_DEV_FLAGS_ASSIGNED;
> +
>  	pci_release_regions(assigned_dev->dev);
>  	pci_disable_device(assigned_dev->dev);
>  	pci_dev_put(assigned_dev->dev);
> diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
> index 62a9caf..cffc530 100644
> --- a/virt/kvm/iommu.c
> +++ b/virt/kvm/iommu.c
> @@ -181,6 +181,8 @@ int kvm_assign_device(struct kvm *kvm,
>  			goto out_unmap;
>  	}
>  
> +	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,
> @@ -209,6 +211,8 @@ int kvm_deassign_device(struct kvm *kvm,
>  
>  	iommu_detach_device(domain, &pdev->dev);
>  
> +	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,
> 
> --
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-- 
Ian Campbell

All progress is based upon a universal innate desire of every organism
to live beyond its income.
		-- Samuel Butler, "Notebooks"

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