Re: [Qemu-devel] [PATCH] ppc: Stop dumping state on all exceptions in linux-user

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Wed, 2016-08-03 at 12:32 +0100, Peter Maydell wrote:
> Yeah, there's an LTP test that fails because of this (we
> send a SIGSEGV when we should be sending a SIGBUS). It's
> a bit painful to fix though, since as you say we've
> effectively thrown away some information. I'm inclined to
> put this in the big pile of "bugs we could fix if we
> ever implemented linux-user-with-softmmu" and otherwise
> ignore it, unless you have a real-world program that
> needs this and makes some kind of bodge fix worthwhile.

Nope, not really...

If we care, a simpler fix would be to add a "translate_user_fault" hook
to the CPU class that takes more info about the original signal than
handle_mmu_fault does, and call it when available (with a fallback)
from user-exec.c

That does mean going through all the cpu_signal_handler() variants in
there though to make them extract more useful info.

Not sure it's worthwhile...

As far user-with-softmmu, I'm not too sure... softmmu significantly
increases the overhead of load and stores. Maybe after we add 128-bit
integers to TGC to alleviate that a bit ? :-)

Cheers,
Ben
.