On 05.09.2013, at 14:49, Alexey Kardashevskiy wrote: > On 09/05/2013 10:16 PM, Alexander Graf wrote: >> >> On 05.09.2013, at 14:04, Alexey Kardashevskiy wrote: >> >>> On 09/05/2013 08:21 PM, Alexander Graf wrote: >>>> >>>> On 05.09.2013, at 12:17, Alexey Kardashevskiy wrote: >>>> >>>>> On 09/05/2013 07:27 PM, Alexander Graf wrote: >>>>>> >>>>>> On 05.09.2013, at 09:40, Alexey Kardashevskiy wrote: >>>>>> >>>>>>> On 09/05/2013 05:08 PM, Alexander Graf wrote: >>>>>>>> >>>>>>>> >>>>>>>> Am 05.09.2013 um 07:58 schrieb Alexey Kardashevskiy <a...@ozlabs.ru>: >>>>>>>> >>>>>>>>> On the real hardware, RTAS is called in real mode and therefore >>>>>>>>> ignores top 4 bits of the address passed in the call. >>>>>>>> >>>>>>>> Shouldn't we ignore the upper 4 bits for every memory access in real >>>>>>>> mode, not just that one parameter? >>>>>>> >>>>>>> We probably should but I just do not see any easy way of doing this. Yet >>>>>>> another "Ignore N bits on the top" memory region type? No idea. >>>>>> >>>>>> Well, it already works for code that runs inside of guest context, >>>>>> because there the softmmu code for real mode strips the upper 4 bits. >>>>>> >>>>>> I basically see 2 ways of fixing this "correctly": >>>>>> >>>>> >>>>>> 1) Don't access memory through cpu_physical_memory_rw or ldx_phys but >>>>>> instead through real mode wrappers that strip the upper 4 bits, similar >>>>>> to how we handle virtual memory differently from physical memory >>>>> >>>>> But there is no a ready wrapper for this, correct? I could not find any. I >>>>> would rather do this, looks nicer than 2). >>>>> >>>>> >>>>>> 2) Create 15 aliases to system_memory at the upper 4 bits of address >>>>>> space. That should at the end of the day give you the same effect >>>>> >>>>> Wow. Is not that too much? >>>>> Ooor since I am normally making bad decisions, I should do this :) >>>>> >>>>> >>>>>> The fix as you're proposing it wouldn't work for indirect memory >>>>>> descriptors. Imagine you have an "address" parameter that gives you a >>>>>> pointer to a struct in memory that again contains a pointer. You still >>>>>> want that pointer be interpreted correctly, no? >>>>> >>>>> Yes I do. I just think that having non zero bits at the top is a bug and I >>>>> would not want the guest to continue sending bad addresses to the host. Or >>>>> at least I want to know if it still happening. >>>>> >>>>> Now we know that the only occasion of this misbehaviour is the "stop-self" >>>>> call and others works just fine. If something new comes up (what is pretty >>>>> unlikely, otherwise we would have noticed this issue a loong time ago AND >>>>> Paul already made&posted a patch for the host to fix __pa() so it is not >>>>> going to happen on new kernels either), ok, we will think of fixing this. >>>>> >>>>> Doing in QEMU what the hardware does is a good thing but here I would >>>>> think >>>>> twice. >>>> >>>> Well, the idea behind RTAS is that everything RTAS does is usually run in >>>> IR=0 DR=0 inside of guest context, so that's the view of the world we >>>> should expose. >>>> >>>> Which makes me think. >>>> >>> >>>> Couldn't we just set IR=0 DR=0 when getting an RTAS call and use the >>>> virtual memory access functions? Those will already strip the upper 4 >>>> bits. >>> >>> Ok. We reached the border where my ignorance starts :) Never could >>> understand the concept of the guest virtual memory in QEMU. >>> >>> So we clear IR/DR and call what API? This is not address_space_rw() and >>> company, right? >> >> Nono, we basically route things through the same accesses that instructions >> inside of guest context would call. Something like >> >> cpu_ldl_data() >> >> for example. IIRC there is also an #ifdef that allows you to just run ldl(). > > cpu_ldl_data() is defined for CONFIG_USER_ONLY. But ok, it is defined > simply as ldl_p(): > > #define cpu_ldl_data(env, addr) ldl_raw(addr) > #define g2h(x) ((void *)((unsigned long)(target_ulong)(x) + GUEST_BASE)) > #define laddr(x) g2h(x) > #define ldl_raw(p) ldl_p(laddr((p))) > > static inline int ldl_p(const void *ptr) > { > int32_t r; > memcpy(&r, ptr, sizeof(r)); > return r; > } > > So it tries accessing memory @ptr (which is the guest physical) and - > crashes :) So I need an address converter which is not there. > > What do I miss? Thanks.
It should be defined through a bunch of macros and incomprehensible #include's and glue()'s for softmmu too. Just try and see if it works for you. > > >> It automatically uses the current virtual layout the same way that the >> instruction emulator would do it - which is pretty much what we want. >> > >> IIRC you also have to enter RTAS calls with DR=0, so we wouldn't even >> need to flip any MSR bits when emulating RTAS calls, right? > > Probably. Right now cpu->env.msr==0x0 in rtas handler but not sure that I > see the real value. Make sure you run cpu_synchronize_state() before you look at cpu->env.msr. Alex