From: David Gibson <david@gibson.dropbear.id.au>
To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Alex Williamson <alex.williamson@redhat.com>,
linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org,
kvm-ppc@vger.kernel.org
Subject: Re: [PATCH kernel] vfio/spapr_tce: Skip unsetting already unset table
Date: Tue, 12 Feb 2019 10:44:03 +1100 [thread overview]
Message-ID: <20190211234402.GA1884@umbus.fritz.box> (raw)
In-Reply-To: <20190211074917.125723-1-aik@ozlabs.ru>
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On Mon, Feb 11, 2019 at 06:49:17PM +1100, Alexey Kardashevskiy wrote:
> VFIO TCE IOMMU v2 owns IOMMU tables so when detach a IOMMU group from
> a container, we need to unset those from a group so we call unset_window()
> so do we unconditionally. We also unset tables when removing a DMA window
> via the VFIO_IOMMU_SPAPR_TCE_REMOVE ioctl.
>
> The window removal checks if the table actually exists (hidden inside
> tce_iommu_find_table()) but the group detaching does not so the user
> may see duplicating messages:
> pci 0009:03 : [PE# fd] Removing DMA window #0
> pci 0009:03 : [PE# fd] Removing DMA window #1
> pci 0009:03 : [PE# fd] Removing DMA window #0
> pci 0009:03 : [PE# fd] Removing DMA window #1
>
> At the moment this is not a problem as the second invocation
> of unset_window() writes zeroes to the HW registers again and exits early
> as there is no table.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>
> When doing VFIO PCI hot unplug, first we remove the DMA window and
> set container->tables[num] - this is a first couple of messages.
> Then we detach the group and then we see another couple of the same
> messages which confused myself.
> ---
> drivers/vfio/vfio_iommu_spapr_tce.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index c424913..8dbb270 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -1235,7 +1235,8 @@ static void tce_iommu_release_ownership_ddw(struct tce_container *container,
> }
>
> for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i)
> - table_group->ops->unset_window(table_group, i);
> + if (container->tables[i])
> + table_group->ops->unset_window(table_group, i);
>
> table_group->ops->release_ownership(table_group);
> }
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2019-02-12 1:54 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-11 7:49 [PATCH kernel] vfio/spapr_tce: Skip unsetting already unset table Alexey Kardashevskiy
2019-02-11 23:44 ` David Gibson [this message]
2019-02-12 20:52 ` Alex Williamson
2019-02-13 0:18 ` Alexey Kardashevskiy
2019-02-19 21:47 ` Alex Williamson
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