From: Nicholas Piggin <npiggin@gmail•com>
To: Alexey Kardashevskiy <aik@ozlabs•ru>
Cc: linuxppc-dev@lists•ozlabs.org,
Alex Williamson <alex.williamson@redhat•com>,
Paul Mackerras <paulus@samba•org>,
David Gibson <david@gibson•dropbear.id.au>
Subject: Re: [PATCH kernel 06/15] powerpc/mm/iommu: Put pages on process exit
Date: Wed, 3 Aug 2016 20:11:04 +1000 [thread overview]
Message-ID: <20160803201104.0d332fab@roar.ozlabs.ibm.com> (raw)
In-Reply-To: <1470213656-1042-7-git-send-email-aik@ozlabs.ru>
On Wed, 3 Aug 2016 18:40:47 +1000
Alexey Kardashevskiy <aik@ozlabs•ru> wrote:
> At the moment VFIO IOMMU SPAPR v2 driver pins all guest RAM pages when
> the userspace starts using VFIO. When the userspace process finishes,
> all the pinned pages need to be put; this is done as a part of
> the userspace memory context (MM) destruction which happens on
> the very last mmdrop().
>
> This approach has a problem that a MM of the userspace process
> may live longer than the userspace process itself as kernel threads
> use userspace process MMs which was runnning on a CPU where
> the kernel thread was scheduled to. If this happened, the MM remains
> referenced until this exact kernel thread wakes up again
> and releases the very last reference to the MM, on an idle system this
> can take even hours.
>
> This references and caches MM once per container and adds tracking
> how many times each preregistered area was registered in
> a specific container. This way we do not depend on @current pointing to
> a valid task descriptor.
>
> This changes the userspace interface to return EBUSY if memory is
> already registered (mm_iommu_get() used to increment the counter);
> however it should not have any practical effect as the only
> userspace tool available now does register memory area once per
> container anyway.
>
> As tce_iommu_register_pages/tce_iommu_unregister_pages are called
> under container->lock, this does not need additional locking.
>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs•ru>
Reviewed-by: Nicholas Piggin <npiggin@gmail•com>
next prev parent reply other threads:[~2016-08-03 10:11 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-03 8:40 [PATCH kernel 00/15] powerpc/kvm/vfio: Enable in-kernel acceleration Alexey Kardashevskiy
2016-08-03 8:40 ` [PATCH kernel 01/15] Revert "iommu: Add a function to find an iommu group by id" Alexey Kardashevskiy
2016-08-15 4:58 ` Paul Mackerras
2016-08-03 8:40 ` [PATCH kernel 02/15] KVM: PPC: Finish enabling VFIO KVM device on POWER Alexey Kardashevskiy
2016-08-04 5:21 ` David Gibson
2016-08-03 8:40 ` [PATCH kernel 03/15] KVM: PPC: Reserve KVM_CAP_SPAPR_TCE_VFIO capability number Alexey Kardashevskiy
2016-08-03 8:40 ` [PATCH kernel 04/15] powerpc/powernv/ioda: Fix TCE invalidate to work in real mode again Alexey Kardashevskiy
2016-08-04 5:23 ` David Gibson
2016-08-09 11:26 ` [kernel, " Michael Ellerman
2016-08-03 8:40 ` [PATCH kernel 05/15] powerpc/iommu: Stop using @current in mm_iommu_xxx Alexey Kardashevskiy
2016-08-03 10:10 ` Nicholas Piggin
2016-08-05 7:00 ` Michael Ellerman
2016-08-09 5:29 ` Alexey Kardashevskiy
2016-08-09 4:43 ` Balbir Singh
2016-08-09 6:04 ` Nicholas Piggin
2016-08-09 6:17 ` Balbir Singh
2016-08-12 2:57 ` David Gibson
2016-08-12 4:56 ` Alexey Kardashevskiy
2016-08-15 10:58 ` David Gibson
2016-08-03 8:40 ` [PATCH kernel 06/15] powerpc/mm/iommu: Put pages on process exit Alexey Kardashevskiy
2016-08-03 10:11 ` Nicholas Piggin [this message]
2016-08-12 3:13 ` David Gibson
2016-08-03 8:40 ` [PATCH kernel 07/15] powerpc/iommu: Cleanup iommu_table disposal Alexey Kardashevskiy
2016-08-12 3:18 ` David Gibson
2016-08-03 8:40 ` [PATCH kernel 08/15] powerpc/vfio_spapr_tce: Add reference counting to iommu_table Alexey Kardashevskiy
2016-08-12 3:29 ` David Gibson
2016-08-03 8:40 ` [PATCH kernel 09/15] powerpc/mmu: Add real mode support for IOMMU preregistered memory Alexey Kardashevskiy
2016-08-12 4:02 ` David Gibson
2016-08-03 8:40 ` [PATCH kernel 10/15] KVM: PPC: Use preregistered memory API to access TCE list Alexey Kardashevskiy
2016-08-12 4:17 ` David Gibson
2016-08-03 8:40 ` [PATCH kernel 11/15] powerpc/powernv/iommu: Add real mode version of iommu_table_ops::exchange() Alexey Kardashevskiy
2016-08-12 4:29 ` David Gibson
2016-08-03 8:40 ` [PATCH kernel 12/15] KVM: PPC: Enable IOMMU_API for KVM_BOOK3S_64 permanently Alexey Kardashevskiy
2016-08-12 4:34 ` David Gibson
2016-08-03 8:40 ` [PATCH kernel 13/15] KVM: PPC: Pass kvm* to kvmppc_find_table() Alexey Kardashevskiy
2016-08-12 4:45 ` David Gibson
2016-08-03 8:40 ` [PATCH kernel 14/15] vfio/spapr_tce: Export container API for external users Alexey Kardashevskiy
2016-08-08 16:43 ` Alex Williamson
2016-08-09 5:19 ` Alexey Kardashevskiy
2016-08-09 12:16 ` Alex Williamson
2016-08-10 5:37 ` Alexey Kardashevskiy
2016-08-10 16:46 ` Alex Williamson
2016-08-12 5:46 ` David Gibson
2016-08-12 6:12 ` Alexey Kardashevskiy
2016-08-15 11:07 ` David Gibson
2016-08-17 8:31 ` Alexey Kardashevskiy
2016-08-12 15:22 ` Alex Williamson
2016-08-17 3:17 ` David Gibson
2016-08-18 0:22 ` Alexey Kardashevskiy
2016-08-29 6:35 ` Alexey Kardashevskiy
2016-08-29 13:27 ` David Gibson
2016-09-07 9:09 ` Alexey Kardashevskiy
2016-09-21 6:56 ` Alexey Kardashevskiy
2016-09-23 7:12 ` David Gibson
2016-10-17 6:06 ` Alexey Kardashevskiy
2016-10-18 1:42 ` David Gibson
2016-08-15 3:59 ` Paul Mackerras
2016-08-15 15:32 ` Alex Williamson
2016-08-12 5:25 ` David Gibson
2016-08-03 8:40 ` [PATCH kernel 15/15] KVM: PPC: Add in-kernel acceleration for VFIO Alexey Kardashevskiy
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