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From: Lucas Stach <l.stach@pengutronix.de>
To: christian.koenig@amd.com,
	Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>,
	"Zhou, David(ChunMing)" <David1.Zhou@amd.com>,
	"amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>
Subject: Re: [PATCH 2/2] drm/scheduler: Remove obsolete spinlock.
Date: Wed, 16 May 2018 15:00:00 +0200	[thread overview]
Message-ID: <1526475600.10230.3.camel@pengutronix.de> (raw)
In-Reply-To: <755d0607-4191-55d2-a21a-9a87305499ad@gmail.com>

Am Mittwoch, den 16.05.2018, 14:32 +0200 schrieb Christian König:
> Am 16.05.2018 um 14:28 schrieb Lucas Stach:
> > Am Mittwoch, den 16.05.2018, 14:08 +0200 schrieb Christian König:
> > > Yes, exactly.
> > > 
> > > For normal user space command submission we should have tons of
> > > locks
> > > guaranteeing that (e.g. just the VM lock should do).
> > > 
> > > For kernel moves we have the mutex for the GTT windows which
> > > protects
> > > it.
> > > 
> > > The could be problems with the UVD/VCE queues to cleanup the
> > > handles
> > > when an application crashes.
> > 
> > FWIW, etnaviv is currently completely unlocked in this path, but I
> > believe that this isn't an issue as the sched fence seq numbers are
> > per
> > entity. So to actually end up with reversed seqnos one context has
> > to
> > preempt itself to do another submit, while the current one hasn't
> > returned from kernel space, which I believe is a fairly theoretical
> > issue. Is my understanding correct?
> 
> Yes. The problem is with the right timing this can be used to access 
> freed up memory.
> 
> If you then manage to place a page table in that freed up memory
> taking 
> over the system is just a typing exercise.

Thanks. I believe we don't have this problem in etnaviv, as memory
referencing is tied to the job and will only be unreferenced on
free_job, but I'll re-check this when I've got some time.

Regards,
Lucas
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  reply	other threads:[~2018-05-16 13:00 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-15 19:31 [PATCH 1/2] drm/amdgpu: Skip drm_sched_entity realted ops for KIQ ring Andrey Grodzovsky
     [not found] ` <1526412674-15913-1-git-send-email-andrey.grodzovsky-5C7GfCeVMHo@public.gmane.org>
2018-05-15 19:31   ` [PATCH 2/2] drm/scheduler: Remove obsolete spinlock Andrey Grodzovsky
     [not found]     ` <1526412674-15913-2-git-send-email-andrey.grodzovsky-5C7GfCeVMHo@public.gmane.org>
2018-05-15 19:38       ` Alex Deucher
     [not found]         ` <CADnq5_Pp=itdSOwq75petxvte1kUcLxmLymp_5zy7LVrgowyVw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-05-15 20:24           ` Andrey Grodzovsky
2018-05-16  3:04       ` zhoucm1
     [not found]         ` <dda4fb88-e228-e10b-46a5-27ba9888b78d-5C7GfCeVMHo@public.gmane.org>
2018-05-16  3:33           ` Grodzovsky, Andrey
     [not found]             ` <MWHPR12MB14530840CD7DB545DD286827EA920-Gy0DoCVfaSWZBIDmKHdw+wdYzm3356FpvxpqHgZTriW3zl9H0oFU5g@public.gmane.org>
2018-05-16  6:50               ` Christian König
     [not found]                 ` <3a54ce0c-6821-9c94-a67f-2b1a3c74959d-5C7GfCeVMHo@public.gmane.org>
2018-05-16 11:15                   ` Andrey Grodzovsky
2018-05-16 11:23                     ` Christian König
     [not found]                       ` <0d936838-8a88-9bd7-d4ff-053cd73f41cc-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2018-05-16 11:47                         ` Andrey Grodzovsky
2018-05-16 12:08                           ` Christian König
     [not found]                             ` <0be3bb9a-004a-7390-469c-3f974ed44055-5C7GfCeVMHo@public.gmane.org>
2018-05-16 12:28                               ` Lucas Stach
     [not found]                                 ` <1526473713.10230.1.camel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2018-05-16 12:32                                   ` Christian König
2018-05-16 13:00                                     ` Lucas Stach [this message]
     [not found]                                       ` <1526475600.10230.3.camel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2018-05-16 13:10                                         ` Christian König
     [not found]                                           ` <96b4e712-5e80-0053-301e-3f89940be8f0-5C7GfCeVMHo@public.gmane.org>
2018-05-16 13:16                                             ` Lucas Stach
2018-05-16 14:25                                               ` Andrey Grodzovsky
2018-05-15 19:42   ` [PATCH 1/2] drm/amdgpu: Skip drm_sched_entity realted ops for KIQ ring Alex Deucher
     [not found]     ` <CADnq5_OtJDxZSrTe_peJtFTCm6T8QnBW-iri2UJv1yvOmjraNQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-05-16  7:05       ` Christian König

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