Re: [PATCH v3 0/6] X86: Alias isa-bios area and clean up

[BALATON Zoltan <balaton@eik.bme.hu>]

On Wed, 8 May 2024, Bernhard Beschow wrote:
> This series changes the "isa-bios" MemoryRegion to be an alias rather than a
> copy in the pflash case. This fixes issuing pflash commands in the isa-bios
> region which matches real hardware and which some real-world legacy bioses I'm
> running rely on. Furthermore, aliasing in the isa-bios area is already the

I wonder if this allows the guest to flash the bios now, replacing or 
breaking it which may be a new security issue. If so this may need some 
machine property to enable it or is that not a problem in practice?

Regards,
BALATON Zoltan

> current behavior in the bios (a.k.a. ROM) case, so this series consolidates
> behavior.
>
> For migration compatibility the aliasing is only performed on new versions of
> the q34 and pc machine types.
>
> v3:
> * Amend commit message with a diff of `info mtree` (Phil)
> * Add comments for bios memory regions (Phil)
>
> v2:
> * Don't leak bios memory regions (Phil)
> * Add compat machinery (Michael)
>
> Testing done:
> * `make check` with qemu-system-x86_64 (QEMU 8.2.2) installed. All tests
>  including migration tests pass.
> * `make check-avocado`
>
> Best regards,
> Bernhard
>
> Bernhard Beschow (6):
>  hw/i386/x86: Eliminate two if statements in x86_bios_rom_init()
>  hw/i386: Have x86_bios_rom_init() take X86MachineState rather than
>    MachineState
>  hw/i386/x86: Don't leak "isa-bios" memory regions
>  hw/i386/x86: Don't leak "pc.bios" memory region
>  hw/i386/x86: Extract x86_isa_bios_init() from x86_bios_rom_init()
>  hw/i386/pc_sysfw: Alias rather than copy isa-bios region
>
> include/hw/i386/pc.h  |  1 +
> include/hw/i386/x86.h | 17 +++++++++++++++-
> hw/i386/microvm.c     |  2 +-
> hw/i386/pc.c          |  1 +
> hw/i386/pc_piix.c     |  3 +++
> hw/i386/pc_q35.c      |  2 ++
> hw/i386/pc_sysfw.c    | 17 ++++++++++------
> hw/i386/x86.c         | 45 ++++++++++++++++++++++---------------------
> 8 files changed, 58 insertions(+), 30 deletions(-)
>
> --
> 2.45.0
>
>
>