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

[Bernhard Beschow]

Am 8. Mai 2024 20:39:28 UTC schrieb 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.

The bios can already be flashed, just from different addresses. This series 
just adds another alias region through which flashing will be possible. AFAICS 
it doesn't impose new security issues.

Ping... The last patch still needs an R-b, the other patches are already on 
master.

Best regards,
Bernhard

> 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
>> 
>> 
>>