Date: Wed, 28 Nov 2018 14:57:19 +0100
From: Samuel Ortiz <sameo@linux.intel.com>
Message-ID: <20181128135719.GE4393@caravaggio>
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Subject: Re: [Qemu-devel] [PATCH 04/13] target: arm: Move all interrupt and
 exception handlers into their own file
To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-arm <qemu-arm@nongnu.org>, Richard Henderson <richard.henderson@linaro.org>, QEMU Developers <qemu-devel@nongnu.org>

On Wed, Nov 28, 2018 at 11:39:57AM +0000, Peter Maydell wrote:
> On Wed, 28 Nov 2018 at 10:40, Samuel Ortiz <sameo@linux.intel.com> wrote:
> > Given that this piece of code effectively builds a dependency to TCG
> > from the KVM code, I see a few solutions but I need your input here. We
> > could:
> >
> > - Decide we don't want to support --disable-tcg for ARM. We'd then carry
> >   this patch serie from the NEMU code repo. Worst case scenario, at
> >   least for us.
> > - Manage to implement exception injection from userspace without TCG.
> >   Would it even be possible?
> > - Offload exception injections back to the kernel in those cases. I feel
> >   this would be the cleanest solution but may need kernel changes.
> 
> The kernel folk were firmly against 3, IIRC, but you can go
> and have the discussion if you like.
> 
> I don't really see what the problem is. This is just a bit
> of code that's used by both TCG and KVM. Therefore it goes
> in the binary whether TCG is enabled or not. Other functions
> and bits of code are TCG only and therefore don't go in a
> KVM-only binary.
Keeping this code with --disable-tcg means:

Keep arm_cpu_do_interrupt -> Keep check_for_semihosting -> Keep the arm
instruction loading code -> Keep a large chunk of the TCG core code
itself. Does that dependency chain looks fine to you?

Cheers,
Samuel.