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

[Palmer Dabbelt <palmer@sifive.com>]

On Thu, 01 Aug 2019 08:39:17 PDT (-0700), Peter Maydell wrote:
> On Wed, 3 Jul 2019 at 09:41, Palmer Dabbelt <palmer@sifive.com> wrote:
>>
>> From: Michael Clark <mjc@sifive.com>
>>
>> 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 <mjc@sifive.com>
>> [Changes by AF:
>>  - Squash two patches and rewrite commit message
>>  - Set baddr to the access address
>> ]
>> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
>> Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
>> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
>
> 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.
>
> 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.