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Re: [Xen-devel] [PATCH v2 01/17] arm: Placeholder for handling Group0/1 traps
Hi,
On 28/03/18 04:48, Manish Jaggi wrote:
On 03/28/2018 06:18 AM, Julien Grall wrote:
Hi,
Sorry for the formatting.
On Wed, 28 Mar 2018, 04:18 Stefano Stabellini, <sstabellini@xxxxxxxxxx
<mailto:sstabellini@xxxxxxxxxx>> wrote:
On Tue, 27 Mar 2018, Marc Zyngier wrote:
> On 27/03/18 11:10, Manish Jaggi wrote:
> >
> >
> > On 03/27/2018 03:31 PM, Marc Zyngier wrote:
> >> On 27/03/18 10:07, Manish Jaggi wrote:
> >>> The errata will require to emulate the GIC virtual CPU
interface in Xen.
> >>> Because the hypervisor will update its internal state of the
vGIC, we want
> >>> to avoid messing up with it. So the errata is handled
separately from the
> >>> rest of the hypervisor.
> >>>
> >>> New file vgic-v3-sr.c is added which will hold trap and
emulate code
> >>> for group0 / group1 registers. Workaround for cavium Errata
30115
> >>> needs this emulation code.
> >>>
> >>> vgic_v3_handle_cpuif_access would be called from
do_trap_guest_sync
> >>> in subsequent patches based on errata macros.
> >>>
> >>> Signed-off-by: Manish Jaggi <manish.jaggi@xxxxxxxxxx
<mailto:manish.jaggi@xxxxxxxxxx>>
> >>> ---
> >>> xen/arch/arm/arm64/vgic-v3-sr.c | 60
+++++++++++++++++++++++++++++++++++++++
> >>> xen/include/asm-arm/arm64/traps.h | 2 ++
> >>> 2 files changed, 62 insertions(+)
> >>> create mode 100644 xen/arch/arm/arm64/vgic-v3-sr.c
> >>>
> >>> diff --git a/xen/arch/arm/arm64/vgic-v3-sr.c
b/xen/arch/arm/arm64/vgic-v3-sr.c
> >>> new file mode 100644
> >>> index 0000000000..39ab1ed6ca
> >>> --- /dev/null
> >>> +++ b/xen/arch/arm/arm64/vgic-v3-sr.c
> >>> @@ -0,0 +1,60 @@
> >>> +/*
> >>> + * xen/arch/arm/arm64/vgic-v3-sr.c
> >>> + *
> >>> + * Code to emulate group0/group1 traps for handling
> >>> + * cavium erratum 30115
> >>> + *
> >>> + * Manish Jaggi <manish.jaggi@xxxxxxxxxx
<mailto:manish.jaggi@xxxxxxxxxx>>
> >>> + * Copyright (c) 2018 Cavium.
> >> IANAL, but I don't think this copyright notice is correct.
> >>
> >> I wrote about 90% of this series, and the copyright for that
code is
> >> owned by ARM, and licensed under the GPLv2. You have the right to
> >> duplicate that code and do almost whatever you want with
(within the
> >> limits of the GPLv2), but you still don't own the copyright.
> >>
> >> I suggest you get in touch with your legal department for
clarification
> >> on the matter.
> > I will remove the copyright line, and add this
> > Original Author: Marc Zyngier <>
> > Ported to Xen by: Manish Jaggi <>
>
> You're missing the point. I don't give a damn about the
authorship (I'm
> not exactly proud to have written that code).
:-D
> The problem at hand is the
> ARM copyright, which should be preserved (as no-one in Cavium
wrote a
> single line of the original code).
I have been asking myself similar questions for a while now when we
import code from Linux. The copyright/author line at the top of
the file
is somewhat arbitrary as every person that touched the code has
copyright over her modifications. This is why at some point I
thought we
had to retain the full list of Signed-off-by lines that ever
touched the
code in question, but then, reading the DCO terms one more time:
(b) The contribution is based upon previous work that, to the best
of my knowledge, is covered under an appropriate open source
license and I have the right under that license to submit that
work with modifications, whether created in whole or in part
by me, under the same open source license (unless I am
permitted to submit under a different license), as indicated
in the file; or
I checked in the Linux kernel when code was imported from the Xen
hypervisor to KVM a long time ago, and only a singled Signed-off-by of
the person importing the code was used.
It does not mean it was a good practice ;).
This is how I came to the conclusion that actually we don't need to do
anything special, although it would be nice as a courtesy to
retain the
copyright/author lines at the top of the file. It would also be
nice to
have the original Linux commit id in the commit message to help
tracking
the history.
We had a similar discussion on the spectre patches a couple of months
ago. The original author is useful to know if we need to relicense
some files.
Having just the commit id from Linux would create more overhead.
Lars suggested to create a file listing where all the work come from.
For commit, I think it would be ok to just add the Signed-off in the
commit and retain copyright in the code.
Of course, it is ok add the Cavium one if code is changed. But no
copyright should be dropped.
How about
+/*
+ * xen/arch/arm/arm64/vgic-v3-sr.c
+ *
+ * Code to emulate group0/group1 traps for handling
+ * cavium erratum 30115
+ *
+ * This file merges code from Linux virt/kvm/arm/hyp/vgic-v3-sr.c
+ * Copyright (C) 2012-2015 - ARM Ltd
+ * Original Author: Marc Zyngier <marc.zyngier@xxxxxxx>
+ * Code Ported to Xen by: Manish Jaggi <manish.jaggi@xxxxxxxxxx>
...
That would be ok for me.
Cheers,
--
Julien Grall
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