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-ppc@vger•kernel.org
Subject: Re: [RFC PATCH kernel] vfio/spapr_tce: Get rid of possible infinite loop
Date: Tue, 2 Oct 2018 14:44:33 +1000 [thread overview]
Message-ID: <20181002044433.GC1886@umbus.fritz.box> (raw)
In-Reply-To: <20181002032231.7494-1-aik@ozlabs.ru>
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On Tue, Oct 02, 2018 at 01:22:31PM +1000, Alexey Kardashevskiy wrote:
> As a part of cleanup, the SPAPR TCE IOMMU subdriver releases preregistered
> memory. If there is a bug in memory release, the loop in
> tce_iommu_release() becomes infinite; this actually happened to me.
>
> This makes the loop finite and prints a warning on every failure to make
> the code more bug prone.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs•ru>
Reviewed-by: David Gibson <david@gibson•dropbear.id.au>
It does improve the current behaviour. I do suspect, however, that
leaving the failed regions in the list will probably cause another
failure later on.
> ---
> drivers/vfio/vfio_iommu_spapr_tce.c | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index b1a8ab3..ece0651 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -371,6 +371,7 @@ static void tce_iommu_release(void *iommu_data)
> {
> struct tce_container *container = iommu_data;
> struct tce_iommu_group *tcegrp;
> + struct tce_iommu_prereg *tcemem, *tmtmp;
> long i;
>
> while (tce_groups_attached(container)) {
> @@ -393,13 +394,8 @@ static void tce_iommu_release(void *iommu_data)
> tce_iommu_free_table(container, tbl);
> }
>
> - while (!list_empty(&container->prereg_list)) {
> - struct tce_iommu_prereg *tcemem;
> -
> - tcemem = list_first_entry(&container->prereg_list,
> - struct tce_iommu_prereg, next);
> - WARN_ON_ONCE(tce_iommu_prereg_free(container, tcemem));
> - }
> + list_for_each_entry_safe(tcemem, tmtmp, &container->prereg_list, next)
> + WARN_ON(tce_iommu_prereg_free(container, tcemem));
>
> tce_iommu_disable(container);
> if (container->mm)
--
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:[~2018-10-02 4:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-02 3:22 [RFC PATCH kernel] vfio/spapr_tce: Get rid of possible infinite loop Alexey Kardashevskiy
2018-10-02 4:44 ` David Gibson [this message]
2018-10-03 18:17 ` Alex Williamson
2018-10-08 7:29 ` Serhii Popovych
2018-10-08 10:18 ` Michael Ellerman
2018-12-19 4:44 ` Alexey Kardashevskiy
2018-12-23 13:28 ` [RFC,kernel] " Michael Ellerman
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