On 12.08.19 15:40, Cornelia Huck wrote:
> On Mon, 12 Aug 2019 09:52:56 +0200
> David Hildenbrand <da...@redhat.com> wrote:
>
>> On 12.08.19 09:12, Thomas Huth wrote:
>>> On 8/5/19 5:29 PM, David Hildenbrand wrote:
>>>> Let's select the ASC before calling the function and use MMU_DATA_LOAD.
>>>> This is a preparation to:
>>>> - Remove the ASC magic depending on the access mode from mmu_translate
>>>> - Implement IEP support, where we could run into access exceptions
>>>> trying to fetch instructions
>>>>
>>>> Signed-off-by: David Hildenbrand <da...@redhat.com>
>>>> ---
>>>> target/s390x/helper.c | 10 +++++++++-
>>>> 1 file changed, 9 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/target/s390x/helper.c b/target/s390x/helper.c
>>>> index 13ae9909ad..08166558a0 100644
>>>> --- a/target/s390x/helper.c
>>>> +++ b/target/s390x/helper.c
>>>> @@ -58,7 +58,15 @@ hwaddr s390_cpu_get_phys_page_debug(CPUState *cs, vaddr
>>>> vaddr)
>>>> vaddr &= 0x7fffffff;
>>>> }
>>>>
>>>> - if (mmu_translate(env, vaddr, MMU_INST_FETCH, asc, &raddr, &prot,
>>>> false)) {
>>>> + /*
>>>> + * We want to read the code, however, not run into access exceptions
>>>
>>> Is this really a safe assumption here that we always use this to
>>> translate code addresses and not data addresses? ... I don't think so.
>>> For example with the "gva2gpa" HMP command, I'd rather expect that it
>>> also works with the secondary space mode...?
>>
>> Well, it's what current code does. I am not changing that behavior.
>
> Agreed, that is not actively breaking something.
>
>>
>> While it is in general broken to have a single interface to debug
>> code+data (which is only a problem on s390x), it makes a lot of sense if
>> you think about single-stepping through disassembled code using the
>> gdbstub. Or dumping code where you crashed.
>
> What about the memsave interface?
I guess the same problem:
"save to disk virtual memory dump starting at @var{addr} of size
@var{size}" - which virtual memory (code vs. data)? These old interface
are really x86 specific (meaning: it made sense this way for x86)
I'd like to note that if our KVM guest is in AR mode, we would now no
longer be able to crash it :) (well, a nice side-effect of instruction
fetches not going via AR mode).
--
Thanks,
David / dhildenb
