From: Jason Gunthorpe <jgg@nvidia.com>
To: Alistair Popple <apopple@nvidia.com>
Cc: rcampbell@nvidia.com, linux-doc@vger.kernel.org,
nouveau@lists.freedesktop.org, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org, hch@infradead.org,
linux-mm@kvack.org, bskeggs@redhat.com, daniel@ffwll.ch,
akpm@linux-foundation.org
Subject: Re: [Nouveau] [PATCH v3 5/8] mm: Device exclusive memory access
Date: Tue, 2 Mar 2021 08:41:52 -0400 [thread overview]
Message-ID: <20210302124152.GF4247@nvidia.com> (raw)
In-Reply-To: <2758096.Z30Q8iEM0t@nvdebian>
On Tue, Mar 02, 2021 at 07:57:58PM +1100, Alistair Popple wrote:
> The intent was a driver could use HMM or some other mechanism to keep PTEs
> synchronised if required. However I just looked at patch 8 in the series again
> and it appears I got this wrong when converting from the old migration
> approach:
>
> + mutex_unlock(&svmm->mutex);
> + ret = nouveau_atomic_range_fault(svmm, drm, args,
> + size, hmm_flags, mm);
>
> The mutex needs to be unlocked after the range fault to ensure the PTE hasn't
> changed. But this ends up being a problem because try_to_protect() calls
> notifiers which need to take that mutex and hence deadlocks.
you have to check the notifier sequence under the mutex and loop
again. The mutex should only cover programming the HW to use the
pages, nothing else.
> However try_to_protect() scans the PTEs again under the PTL so checking the
> mapping of interest actually gets replaced during the rmap walk seems like a
> reasonable solution. Thanks for the comments.
It does seem cleaner if you can manage it, the notifier will still be
needd to program the HW though
Jason
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next prev parent reply other threads:[~2021-03-02 12:42 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-26 7:18 [Nouveau] [PATCH v3 0/8] Add support for SVM atomics in Nouveau Alistair Popple
2021-02-26 7:18 ` [Nouveau] [PATCH v3 1/8] mm: Remove special swap entry functions Alistair Popple
2021-02-26 15:59 ` Christoph Hellwig
2021-03-02 8:52 ` Alistair Popple
2021-03-02 12:02 ` Alistair Popple
2021-03-01 17:46 ` Jason Gunthorpe
2021-03-02 0:21 ` Alistair Popple
2021-02-26 7:18 ` [Nouveau] [PATCH v3 2/8] mm/swapops: Rework swap entry manipulation code Alistair Popple
2021-02-26 16:00 ` Christoph Hellwig
2021-03-01 17:47 ` Jason Gunthorpe
2021-02-26 7:18 ` [Nouveau] [PATCH v3 3/8] mm/rmap: Split try_to_munlock from try_to_unmap Alistair Popple
2021-02-26 16:01 ` Christoph Hellwig
2021-03-01 16:10 ` Jason Gunthorpe
2021-03-04 4:27 ` Alistair Popple
2021-02-26 7:18 ` [Nouveau] [PATCH v3 4/8] mm/rmap: Split migration into its own function Alistair Popple
2021-02-26 16:03 ` Christoph Hellwig
2021-03-02 22:08 ` Zi Yan
2021-03-04 23:54 ` Alistair Popple
2021-02-26 7:18 ` [Nouveau] [PATCH v3 5/8] mm: Device exclusive memory access Alistair Popple
2021-03-01 17:54 ` Jason Gunthorpe
2021-03-01 22:55 ` Ralph Campbell
2021-03-02 0:05 ` Jason Gunthorpe
2021-03-02 8:57 ` Alistair Popple
2021-03-02 12:41 ` Jason Gunthorpe [this message]
2021-03-04 5:20 ` Alistair Popple
2021-02-26 7:18 ` [Nouveau] [PATCH v3 6/8] mm: Selftests for exclusive device memory Alistair Popple
2021-03-01 17:55 ` Jason Gunthorpe
2021-03-01 18:07 ` Ralph Campbell
2021-03-01 23:14 ` Ralph Campbell
2021-03-02 9:12 ` Alistair Popple
2021-02-26 7:18 ` [Nouveau] [PATCH v3 7/8] nouveau/svm: Refactor nouveau_range_fault Alistair Popple
2021-02-26 7:18 ` [Nouveau] [PATCH v3 8/8] nouveau/svm: Implement atomic SVM access Alistair Popple
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