linux-kernel - Re: [PATCH] iommu/dart: Clear sid2group entry when a group is freed

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Message-ID: <87wnn6t6t4.wl-maz@kernel.org>
Date:   Fri, 24 Sep 2021 14:57:27 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Sven Peter <sven@...npeter.dev>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/dart: Clear sid2group entry when a group is freed

On Fri, 24 Sep 2021 14:45:02 +0100,
Sven Peter <sven@...npeter.dev> wrote:
> 
> sid2groups keeps track of which stream id combinations belong to a
> iommu_group to assign those correctly to devices.
> When a iommu_group is freed a stale pointer will however remain in
> sid2groups. This prevents devices with the same stream id combination
> to ever be attached again (see below).
> Fix that by creating a shadow copy of the stream id configuration
> when a group is allocated for the first time and clear the sid2group
> entry when that group is freed.
> 
>   # echo 1 >/sys/bus/pci/devices/0000\:03\:00.0/remove
>   pci 0000:03:00.0: Removing from iommu group 1
>   # echo 1 >/sys/bus/pci/rescan
>   [...]
>   pci 0000:03:00.0: BAR 0: assigned [mem 0x6a0000000-0x6a000ffff 64bit pref]
>   pci 0000:03:00.0: BAR 2: assigned [mem 0x6a0010000-0x6a001ffff 64bit pref]
>   pci 0000:03:00.0: BAR 6: assigned [mem 0x6c0100000-0x6c01007ff pref]
>   tg3 0000:03:00.0: Failed to add to iommu group 1: -2
>   [...]
> 
> Fixes: 46d1fb072e76b161 ("iommu/dart: Add DART iommu driver")
> Reported-by: Marc Zyngier <maz@...nel.org>
> Signed-off-by: Sven Peter <sven@...npeter.dev>

Thanks for posting this.

Tested-by: Marc Zyngier <maz@...nel.org>

	M.

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