Re: [Qemu-devel] [PATCH v6 06/26] RISC-V: Mark ROM read-only after copying in code

[Michael Clark]

On Sun, Mar 25, 2018 at 5:47 AM, Peter Maydell <address@hidden>
wrote:

> On 25 March 2018 at 00:23, Michael Clark <address@hidden> wrote:
> >
> >
> > On Sat, Mar 24, 2018 at 2:23 PM, Peter Maydell <address@hidden
> >
> > wrote:
> >>
> >> On 24 March 2018 at 18:13, Michael Clark <address@hidden> wrote:
> >> > The sifive_u machine already marks its ROM readonly. This fixes
> >> > the remaining boards.
> >> >
> >> > Cc: Sagar Karandikar <address@hidden>
> >> > Cc: Bastian Koppelmann <address@hidden>
> >> > Signed-off-by: Michael Clark <address@hidden>
> >> > Signed-off-by: Palmer Dabbelt <address@hidden>
> >> > ---
> >> >  hw/riscv/sifive_u.c      |  9 +++++----
> >> >  hw/riscv/spike.c         | 18 ++++++++++--------
> >> >  hw/riscv/virt.c          |  7 ++++---
> >> >  include/hw/riscv/spike.h |  8 --------
> >> >  4 files changed, 19 insertions(+), 23 deletions(-)
> >> >
> >> > diff --git a/hw/riscv/sifive_u.c b/hw/riscv/sifive_u.c
> >> > index 6116c38..25df16c 100644
> >> > --- a/hw/riscv/sifive_u.c
> >> > +++ b/hw/riscv/sifive_u.c
> >> > @@ -223,7 +223,7 @@ static void riscv_sifive_u_init(MachineState
> >> > *machine)
> >> >      SiFiveUState *s = g_new0(SiFiveUState, 1);
> >> >      MemoryRegion *sys_memory = get_system_memory();
> >> >      MemoryRegion *main_mem = g_new(MemoryRegion, 1);
> >> > -    MemoryRegion *boot_rom = g_new(MemoryRegion, 1);
> >> > +    MemoryRegion *mask_rom = g_new(MemoryRegion, 1);
> >> >
> >> >      /* Initialize SOC */
> >> >      object_initialize(&s->soc, sizeof(s->soc),
> TYPE_RISCV_HART_ARRAY);
> >> > @@ -246,10 +246,10 @@ static void riscv_sifive_u_init(MachineState
> >> > *machine)
> >> >      create_fdt(s, memmap, machine->ram_size,
> machine->kernel_cmdline);
> >> >
> >> >      /* boot rom */
> >> > -    memory_region_init_ram(boot_rom, NULL, "riscv.sifive.u.mrom",
> >> > +    memory_region_init_ram(mask_rom, NULL, "riscv.sifive.u.mrom",
> >> >                             memmap[SIFIVE_U_MROM].base, &error_fatal);
> >> > -    memory_region_set_readonly(boot_rom, true);
> >> > -    memory_region_add_subregion(sys_memory, 0x0, boot_rom);
> >> > +    memory_region_set_readonly(mask_rom, true);
> >> > +    memory_region_add_subregion(sys_memory, 0x0, mask_rom);
> >>
> >> memory_region_init_ram + memory_region_set_readonly is
> >> equivalent to memory_region_init_rom.
> >>
> >> >      if (machine->kernel_filename) {
> >> >          load_kernel(machine->kernel_filename);
> >> > @@ -279,6 +279,7 @@ static void riscv_sifive_u_init(MachineState
> >> > *machine)
> >> >      qemu_fdt_dumpdtb(s->fdt, s->fdt_size);
> >> >      cpu_physical_memory_write(memmap[SIFIVE_U_MROM].base +
> >> >          sizeof(reset_vec), s->fdt, s->fdt_size);
> >> > +    memory_region_set_readonly(mask_rom, true);
> >>
> >> Rather than doing this, you should use
> >> rom_add_blob_fixed(). That works even on ROMs which
> >> means you can just create them as read-only from the
> >> start rather than waiting til you've written to them
> >> and then marking them read-only. It also means that
> >> you get the contents correctly reset on reset, even
> >> if the user has been messing with their contents
> >> via the debugger or something.
> >>
> >> hw/arm/boot.c has code which (among a lot of other
> >> things) loads initial kernels and dtb images into
> >> guest memory. You can also find ppc code doing
> >> similar things.
> >
> >
> > I don't mind to make this change, however it is a case of good vs
> perfect.
> > Currently we have some machines with writable ROM sections, this change
> > fixes it and has been tested.
>
> Yes, I would put this on your set of things to
> address for 2.13.
>

Okay. It's on my list...

I will be replying to the other thread with a list of the oustanding
patches, whether they are bug fixes vs cleanups, and whether they are
reviewed.

The mstatus.FS fix is relatively critical and Igor's cpu init actually
fixes a bug with -cpu list. In any case I'll send a list shortly...