Got it Phil, thank you very much! I need to educate myself on the subject of TLB and MMU for mips. //hinko
On Fri, Sep 10, 2021 at 5:30 PM Philippe Mathieu-Daudé <f4...@amsat.org> wrote: > On 9/10/21 3:21 PM, Hinko Kocevar wrote: > > I'm trying to add an I/O memory region to mipssim machine to emulate a > > MMIO region used by the u-boot loaded as BIOS image. I can confirm that > > the machine starts and loads the BIOS, starts execution but hangs due to > > unhandled IO access as described below. > > > > The region should be at 0xB8810000, of size 0x10000. > > > > I've added these lines of code to mispsim.c mips_mipssim_init(): > > > > my_state *s = g_malloc0(sizeof(my_state)); > > memory_region_init_io(&s->mmio, NULL, &my_ops, s, > > "mips_mipssim.foo", 0x10000); > > memory_region_add_subregion(address_space_mem, 0xB8810000LL, > &s->mmio); > > You need to map your device at its physical address, not the virtual > one. > > > All goes well, the machine starts, and I can see the newly added region > > in qemu monitor info mtree output like so: > > > > 00000000b8810000-00000000b881ffff (prio 0, i/o): mips_mipssim.foo > > > > With some tracing enabled I see this error: > > > > Invalid access at addr 0x18810104, size 4, region '(null)', reason: > > rejected > > > > I know the u-boot is making request to 0xB8810104 and not 0x18810104. I > > U-boot accessed the virtual address which is resolved into the physical > one (where your device should be mapped). > > > also can see 0xB8810104 address being handed to io_writex(), but > > mr_offset becomes 0x18810104 here: > > > > mr_offset = (iotlbentry->addr & TARGET_PAGE_MASK) + addr; > > > > What is going on? > > > > FWIW, I can place my emulated memory region at 0x18810104, but would > > like to understand the behavior above. > > Yes, this is the correct address to map it. > > Maybe this helps: > https://training.mips.com/basic_mips/PDF/Memory_Map.pdf > > Regards, > > Phil. > -- .. the more I see the less I believe.., AE AoR
