netdev - Re: [net-next 1/8] pci: Add flag indicating device has been assigned by KVM

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Message-ID: <CAL3LdT7jDfytZD7WESmiHxvpmxKTEZ=uWRjzgsR9e4GtBPE31A@mail.gmail.com>
Date:	Thu, 22 Sep 2011 21:16:18 -0700
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	davem@...emloft.net,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
	"ijc@...lion.org.uk" <ijc@...lion.org.uk>,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	Greg Rose <gregory.v.rose@...el.com>, netdev@...r.kernel.org,
	gospo@...hat.com, Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	linux-pci@...r.kernel.org
Subject: Re: [net-next 1/8] pci: Add flag indicating device has been assigned
 by KVM

On Wed, Sep 21, 2011 at 03:12, Jeff Kirsher <jeffrey.t.kirsher@...el.com> wrote:
> From: Greg Rose <gregory.v.rose@...el.com>
>
> 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>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> ---
>  include/linux/pci.h     |    2 ++
>  virt/kvm/assigned-dev.c |    2 ++
>  virt/kvm/iommu.c        |    4 ++++
>  3 files changed, 8 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index f27893b..4f511da 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 4e9eaeb..eaf3a50 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 78c80f6..967aba1 100644
> --- a/virt/kvm/iommu.c
> +++ b/virt/kvm/iommu.c
> @@ -187,6 +187,8 @@ 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,
> @@ -215,6 +217,8 @@ 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,
> --
> 1.7.6.2

Jesse/Konrad/Ian-

I sent this patch out as part of a pull request for David Miller's
net-next tree.  I know that Greg sent this originally out to the
linux-pci mailing list as a RFC. Since Greg also has a patch against
ixgbe which implemented this flag, I sent both patches for inclusion
into David Miller's net-next.

Dave is wanting to ensure that the PCI maintainers have reviewed this
and are ok with it before pulls my series of patches.

-- 
Cheers,
Jeff
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