linux-kernel - Re: [PATCH v2 0/2] intel-iommu: Fix domain

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Date:	Thu, 17 Feb 2011 15:13:47 -0500
From:	Don Dutile <ddutile@...hat.com>
To:	Alex Williamson <alex.williamson@...hat.com>
CC:	dwmw2@...radead.org, iommu@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	chrisw@...hat.com
Subject: Re: [PATCH v2 0/2] intel-iommu: Fix domain_ids exhaustion

Alex Williamson wrote:
> When we unbind a device from a driver, we don't properly unlink
> the domain from the iommu, so we never free the domain id it
> was using.  We're typically limited to something like 256 domain
> ids, so a loop of unbinding and rebinding a device can exhaust
> this pretty quickly.  If we're assigning the device to a KVM
> guest, libvirt does exactly this each time the device is removed
> from the host driver or added back.  When we do run out, we oops
> the kernel.  Fix these.
> 
> v2:
> 
> We only want to call domain_exit() for domains automatically created
> via the dma ops path.  VM and SI domains have their own life cycle
> and should not be destroyed here.  With v1, if a device was unbound
> from pci-stub while assigned to a VM, the kernel would oops on the
> next call into iommu ops.
> 
> BTW, should we even be removing the device from the domain in the
> VM domain case?  Drivers and VM domains are (unfortunately) orthogonal
> concepts here with the way KVM is currently wired.  Thanks,
> 
> Alex
> 
> ---
> 
> Alex Williamson (2):
>       intel-iommu: Fix get_domain_for_dev() error path
>       intel-iommu: Unlink domain from iommu
> 
> 
>  drivers/pci/intel-iommu.c |   15 +++++++++++++--
>  1 files changed, 13 insertions(+), 2 deletions(-)
> --
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Acked-by: Donald Dutile <ddutile@...hat.com>

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