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SubjectRe: [PATCH] pci, dmar: flush IOTLB before exit domain
On 2011-05-18 03:57, Alex Williamson wrote:
> On Tue, 2011-05-17 at 13:41 -0600, Alex Williamson wrote:
>> On Mon, 2011-05-16 at 09:13 -0600, Alex Williamson wrote:
>>> On Mon, 2011-05-09 at 15:48 +0100, David Woodhouse wrote:
>>>> On Thu, 2011-05-05 at 18:13 -0700, Yinghai Lu wrote:
>>>>> @@ -3252,6 +3252,9 @@ static int device_notifier(struct notifi
>>>>> return 0;
>>>>>
>>>>> if (action == BUS_NOTIFY_UNBOUND_DRIVER && !iommu_pass_through) {
>>>>> + /* before we remove dev with domain, flush IOTLB */
>>>>> + flush_unmaps();
>>>>> +
>>>>> domain_remove_one_dev_info(domain, pdev);
>>>>>
>>>>> if (!(domain->flags & DOMAIN_FLAG_VIRTUAL_MACHINE) &&
>>>>
>>>> That calls flush_unmaps() without the async_umap_flush_lock held,
>>>> doesn't it? A few days ago I asked someone else to test this candidate
>>>> patch for a similar issue:
>>>>
>>>> http://david.woodhou.se/flush-unmaps-on-unbind.patch
>>>
>>> Copying here:
>>>
>>>> diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
>>>> index d552d2c..7e606d6 100644
>>>> --- a/drivers/pci/intel-iommu.c
>>>> +++ b/drivers/pci/intel-iommu.c
>>>> @@ -3256,8 +3259,10 @@ static int device_notifier(struct notifier_block *nb,
>>>>
>>>> if (!(domain->flags & DOMAIN_FLAG_VIRTUAL_MACHINE) &&
>>>> !(domain->flags & DOMAIN_FLAG_STATIC_IDENTITY) &&
>>>> - list_empty(&domain->devices))
>>>> + list_empty(&domain->devices)) {
>>>> + flush_unmaps_timeout(0);
>>>> domain_exit(domain);
>>>> + }
>>>> }
>>>>
>>>> return 0;
>>>> @@ -3587,6 +3592,7 @@ static void intel_iommu_domain_destroy(struct iommu_domain *domain)
>>>> struct dmar_domain *dmar_domain = domain->priv;
>>>>
>>>> domain->priv = NULL;
>>>> + flush_unmaps_timeout(0);
>>>> vm_domain_exit(dmar_domain);
>>>> }
>>>
>>> David, would it be worthwhile to push the unmaps into the
>>> {vm_}domain_exit() functions to avoid races like this in the future? I
>>> can verify the above resolves a panic after unbinding a device from
>>> snd_hda_intel that I hit recently. Do you plan to push this for .39?
>>
>> BTW, is this second chunk really needed? VM iommu mappings don't seem
>> to use the lazy unmap path. Thanks,
>
> David, what do you think of this instead? Thanks,
>
> Alex
>
> intel-iommu: Flush unmaps at domain_exit
>
> From: Alex Williamson <alex.williamson@redhat.com>
>
> We typically batch unmaps to be lazily flushed out at
> regular intervals. When we destroy a domain, we need
> to force a flush of these lazy unmaps to be sure none
> reference the domain we're about to free.
>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>
> drivers/pci/intel-iommu.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
>
> diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
> index d552d2c..b04f84e 100644
> --- a/drivers/pci/intel-iommu.c
> +++ b/drivers/pci/intel-iommu.c
> @@ -1416,6 +1416,10 @@ static void domain_exit(struct dmar_domain *domain)
> if (!domain)
> return;
>
> + /* Flush any lazy unmaps that may reference this domain */
> + if (!intel_iommu_strict)
> + flush_unmaps_timeout(0);
> +
> domain_remove_dev_info(domain);
> /* destroy iovas */
> put_iova_domain(&domain->iovad);
>
>

Can we get this resolved for 2.6.39.1? Via David's patch, or Alex's
(which works for me), or whatever. It's a really annoying regression of
.39 when you want to run with IOMMU enabled.

Thanks,
Jan

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