On Wed, Aug 22, 2012 at 08:02:11AM +0200, Alexander Graf wrote: > > On 22.08.2012, at 07:57, David Gibson wrote: > > > On Wed, Aug 22, 2012 at 07:55:31AM +0200, Alexander Graf wrote: > >> > >> On 22.08.2012, at 06:59, David Gibson wrote: > >> > >>> cpu_physical_memory_write_rom(), despite the name, can also be used to > >>> write images into RAM - and will often be used that way if the machine > >>> uses load_image_targphys() into RAM addresses. > >>> > >>> However, cpu_physical_memory_write_rom(), unlike cpu_physical_memory_rw() > >>> does invalidate any cached TBs which might be affected by the region > >>> written. > >>> > >>> This was breaking reset (under full emu) on the pseries machine - we > >>> loaded > >>> our firmware image into RAM, and while executing it rewrite the code at > >>> the entry point (correctly causing a TB invalidate/refresh). When we > >>> reset the firmware image was reloaded, but the TB from the rewrite was > >>> still active and caused us to get an illegal instruction trap. > >>> > >>> This patch fixes the bug by duplicating the tb invalidate code from > >>> cpu_physical_memory_rw() in cpu_physical_memory_write_rom(). > >>> > >>> Signed-off-by: David Gibson <da...@gibson.dropbear.id.au> > >>> --- > >>> exec.c | 7 +++++++ > >>> 1 file changed, 7 insertions(+) > >>> > >>> diff --git a/exec.c b/exec.c > >>> index 5834766..eff40d7 100644 > >>> --- a/exec.c > >>> +++ b/exec.c > >>> @@ -3523,6 +3523,13 @@ void > >>> cpu_physical_memory_write_rom(target_phys_addr_t addr, > >>> /* ROM/RAM case */ > >>> ptr = qemu_get_ram_ptr(addr1); > >>> memcpy(ptr, buf, l); > >>> + if (!cpu_physical_memory_is_dirty(addr1)) { > >>> + /* invalidate code */ > >>> + tb_invalidate_phys_page_range(addr1, addr1 + l, 0); > >>> + /* set dirty bit */ > >>> + cpu_physical_memory_set_dirty_flags( > >>> + addr1, (0xff & ~CODE_DIRTY_FLAG)); > >>> + } > >> > >> Can't we just call cpu_physical_memory_rw in the RAM case? The > >> function only tries to not do MMIO accesses on ROM pages, right? > > > > Maybe. It's not clear at all to me what cases > > cpu_physical_memory_write_rom() is supposed to be for, as opposed to > > just using cpu_physical_memory_rw(). > > I can only guess, but the code looks to me as if it wants to be a > nop on ROM pages, while basically doing cpu_physical_memory_rw for > RAM pages. Usually in QEMU, every non-RAM page gets treated as MMIO > which might eventually lead to machine checks.
Maybe. Anthony, can you make a ruling on this, or tell me who can. I don't really care how I fix it, but it's definitely broken right now. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson