On 2012-08-22 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().
write_rom ignores write protection - that you usually find on ROMs. That makes no difference under KVM so far as there we lack read-only sections. But that will be fixed soon, patches are on the list. Jan
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