Re: [Qemu-devel] [PATCH] cpu_physical_memory_write_rom() needs to do TB invalidates

[Alexander Graf]

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 <address@hidden>
> ---
> 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?


Alex