Re: [Qemu-riscv] [Qemu-devel] [PULL 04/32] target/riscv: Implement riscv_cpu_unassigned_access

[Alistair Francis]

On Tue, Aug 13, 2019 at 3:44 PM Palmer Dabbelt <address@hidden> wrote:
>
> On Thu, 01 Aug 2019 08:39:17 PDT (-0700), Peter Maydell wrote:
> > On Wed, 3 Jul 2019 at 09:41, Palmer Dabbelt <address@hidden> wrote:
> >>
> >> From: Michael Clark <address@hidden>
> >>
> >> This patch adds support for the riscv_cpu_unassigned_access call
> >> and will raise a load or store access fault.
> >>
> >> Signed-off-by: Michael Clark <address@hidden>
> >> [Changes by AF:
> >>  - Squash two patches and rewrite commit message
> >>  - Set baddr to the access address
> >> ]
> >> Signed-off-by: Alistair Francis <address@hidden>
> >> Reviewed-by: Palmer Dabbelt <address@hidden>
> >> Signed-off-by: Palmer Dabbelt <address@hidden>
> >
> > Oops, I missed seeing this go by. The do_unassigned_access
> > hook is deprecated and you should drop this and use
> > the do_transaction_failed hook instead.

Argh!

> >
> > The distinction between the two is that do_unassigned_access
> > will end up being called for any failing access, including
> > not just "normal" guest accesses but also for bad accesses
> > that happen during page table walks (which often want to
> > be reported to the guest differently) and also accesses
> > by random devices like DMA controllers (where throwing a
> > cpu exception is always a bug).
> >
> > Changing the hook implementation itself should be straightforward;
> > commit 6ad4d7eed05a1e23537f is an example of doing that on Alpha.
> > You also want to check all the places in your target code that
> > do physical memory accesses, determine what the right behaviour
> > if they get a bus fault is, and implement that (or at least put
> > in TODO comments).
>
> Sorry, updating that has been on my TODO list for a while now.  I figured it
> was better to have the deprecated version in there than nothing at all.  I've
> written some patches to fix this, but I want to give them another look before
> sending them out.

I was going to start looking into this, but if you already have
patches I won't bother. Let me know if you want a hand with the
conversion.

Alistair

>