Message-ID: <0df5f0f601e0177e64b65e643affd46939e231f6.camel@mediatek.com>
Date:   Mon, 22 May 2023 04:32:36 +0000
From:   Yi-De Wu (吳一德) <Yi-De.Wu@...iatek.com>
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Subject: Re: [PATCH v2 5/7] virt: geniezone: Add irqchip support for virtual
 interrupt injection

On Fri, 2023-05-12 at 10:57 +0100, Marc Zyngier wrote:
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
> 
> 
> On Fri, 12 May 2023 09:16:58 +0100,
> "Yi-De Wu (吳一德)" <Yi-De.Wu@...iatek.com> wrote:
> > 
> > On Fri, 2023-05-12 at 08:51 +0100, Marc Zyngier wrote:
> > > External email : Please do not click links or open attachments
> > > until
> > > you have verified the sender or the content.
> > > 
> > > 
> > > On Fri, 12 May 2023 08:19:31 +0100,
> > > "Yi-De Wu (吳一德)" <Yi-De.Wu@...iatek.com> wrote:
> > > > 
> > > > On Fri, 2023-04-28 at 19:59 +0100, Marc Zyngier wrote:
> > > > > External email : Please do not click links or open
> > > > > attachments
> > > > > until
> > > > > you have verified the sender or the content.
> > > > > 
> > > > > 
> > > > > On 2023-04-28 11:36, Yi-De Wu wrote:
> > > > > > From: "Yingshiuan Pan" <yingshiuan.pan@...iatek.com>
> > > > > > 
> > > > > > Enable GenieZone to handle virtual interrupt injection
> > > > > > request.
> > > > > > 
> > > > > > Signed-off-by: Yingshiuan Pan <yingshiuan.pan@...iatek.com>
> > > > > > Signed-off-by: Yi-De Wu <yi-de.wu@...iatek.com>
> > > > > > ---
> > > > > >  arch/arm64/geniezone/Makefile       |  2 +-
> > > > > >  arch/arm64/geniezone/gzvm_arch.c    | 24 ++++++--
> > > > > >  arch/arm64/geniezone/gzvm_arch.h    | 11 ++++
> > > > > >  arch/arm64/geniezone/gzvm_irqchip.c | 88
> > > > > > +++++++++++++++++++++++++++++
> > > > > >  drivers/virt/geniezone/gzvm_vm.c    | 75
> > > > > > ++++++++++++++++++++++++
> > > > > >  include/linux/gzvm_drv.h            |  4 ++
> > > > > >  include/uapi/linux/gzvm.h           | 38 ++++++++++++-
> > > > > >  7 files changed, 235 insertions(+), 7 deletions(-)
> > > > > >  create mode 100644 arch/arm64/geniezone/gzvm_irqchip.c
> > > > > 
> > > > > [...]
> > > > > 
> > > > > > +++ b/arch/arm64/geniezone/gzvm_irqchip.c
> > > > > > @@ -0,0 +1,88 @@
> > > > > > +// SPDX-License-Identifier: GPL-2.0
> > > > > > +/*
> > > > > > + * Copyright (c) 2023 MediaTek Inc.
> > > > > > + */
> > > > > > +
> > > > > > +#include <linux/irqchip/arm-gic-v3.h>
> > > > > > +#include <kvm/arm_vgic.h>
> > > > > 
> > > > > NAK.
> > > > > 
> > > > > There is no way you can rely on anything from KVM in
> > > > > your own hypervisor code.
> > > > > 
> > > > 
> > > > Same with previous discussion, we'd like to copy or rename the
> > > > related
> > > > part from KVM and keep the maintainance at our own if it's ok.
> > > 
> > > Why do you need *ANY* of the KVM stuff? Please fully enumerate
> > > these
> > > dependencies and why you have them.
> > > 
> > > Directly using KVM stuff for something completely unrelated is
> > > not
> > > OK,
> > > and will never be.
> > > 
> > >         M.
> > > 
> > > --
> > > Without deviation from the norm, progress is not possible.
> > 
> > The particular part we'd like to leverage from KVM are as followed
> > 1. `gfn_to_pfn_memslot` to convert guest physical address(or
> > intermediate physical address) to physical address
> 
> What is a memslot in your hypervisor? How does it relate to KVM's?
> What about the use of struct kvm?
> 
> I'm sorry, but your use of *internal* structures and API would make
> it
> impossible for us to make any further change without potentially
> affecting your hypervisor. Which is closed source and untestable.
> 
> To sum it up, I'm strongly opposed to any use of these data
> structures.  If you can spot some commonalities, expose them as a
> 0-cost abstraction. But don't use them as is your code.
> 
> > 2. get ARM's number of interrupt of different types e.g. number of
> > SGI,
> > number of PPI...etc
> 
> These are architectural constants, and you can define your own. That
> will cost you nothing but a handful of #define, and keep the two
> subsystem independent.
> 
>         M.
> 
> --
> Without deviation from the norm, progress is not possible.

As per discussion, we would define our own constants here and keep the
subsystem indepedent.

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