Jan Kiszka <jan.kis...@siemens.com> writes:
> On 2012-10-12 15:41, Anthony Liguori wrote:
>> Jan Kiszka <jan.kis...@siemens.com> writes:
>>
>>> On 2012-10-08 20:52, Anthony Liguori wrote:
>>>> Jan Kiszka <jan.kis...@siemens.com> writes:
>>>>
>>>>> On 2012-09-11 17:53, Jan Kiszka wrote:
>>>>>> Our one and only BIOS depends on a writable shadowed BIOS in the ISA
>>>>>> range. As we have no interface to control the write property, make that
>>>>>> region writable by default.
>>>>>>
>>>>>> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
>>>>>> ---
>>>>>>
>>>>>> This unbreaks isapc for TCG, and keep it working for KVM once it starts
>>>>>> supporting read-only memslots.
>>>>>>
>>>>>> hw/pc_sysfw.c | 13 +++++++++----
>>>>>> 1 files changed, 9 insertions(+), 4 deletions(-)
>>>>>>
>>>>>> diff --git a/hw/pc_sysfw.c b/hw/pc_sysfw.c
>>>>>> index b45f0ac..027d98a 100644
>>>>>> --- a/hw/pc_sysfw.c
>>>>>> +++ b/hw/pc_sysfw.c
>>>>>> @@ -136,6 +136,7 @@ static void old_pc_system_rom_init(MemoryRegion
>>>>>> *rom_memory)
>>>>>> {
>>>>>> char *filename;
>>>>>> MemoryRegion *bios, *isa_bios;
>>>>>> + void *isa_bios_ptr;
>>>>>> int bios_size, isa_bios_size;
>>>>>> int ret;
>>>>>>
>>>>>> @@ -167,19 +168,23 @@ static void old_pc_system_rom_init(MemoryRegion
>>>>>> *rom_memory)
>>>>>> g_free(filename);
>>>>>> }
>>>>>>
>>>>>> - /* map the last 128KB of the BIOS in ISA space */
>>>>>> + /* Shadow the last 128KB of the BIOS in ISA space as RAM -
>>>>>> + * Seabios depends on this */
>>>>>> isa_bios_size = bios_size;
>>>>>> if (isa_bios_size > (128 * 1024)) {
>>>>>> isa_bios_size = 128 * 1024;
>>>>>> }
>>>>>> isa_bios = g_malloc(sizeof(*isa_bios));
>>>>>> - memory_region_init_alias(isa_bios, "isa-bios", bios,
>>>>>> - bios_size - isa_bios_size, isa_bios_size);
>>>>>> + memory_region_init_ram(isa_bios, "isa-bios", isa_bios_size);
>>>>>> + vmstate_register_ram_global(isa_bios);
>>>>>> memory_region_add_subregion_overlap(rom_memory,
>>>>>> 0x100000 - isa_bios_size,
>>>>>> isa_bios,
>>>>>> 1);
>>>>>> - memory_region_set_readonly(isa_bios, true);
>>>>>> +
>>>>>> + /* copy ISA rom image from top of the ROM */
>>>>>> + isa_bios_ptr = memory_region_get_ram_ptr(isa_bios);
>>>>>> + rom_copy(isa_bios_ptr, (uint32_t)(-isa_bios_size), isa_bios_size);
>>>>>>
>>>>>> /* map all the bios at the top of memory */
>>>>>> memory_region_add_subregion(rom_memory,
>>>>>>
>>>>>
>>>>> Ping. Or already queued?
>>>>
>>>> I've got it queued now. Thanks.
>>>
>>> I'm withdrawing it: This breaks Windows 95 booting. For unknown reasons,
>>> this nice OS decided to overwrite the F-segment during boot. That is
>>> fine as long as it is properly protected. But it breaks under current
>>> KVM and with the patch above for the isapc. So we need a firmware
>>> interface to enable/disable write protection for this segment in isapc
>>> mode, specifically as that machine targets these old OSes.
>>
>> Ah, if it wasn't for a build break caused by one of the pull requests, I
>> would have pushed last night. Thanks for the heads up, I'll remove it
>> from my queue.
>>
>> Is fw_cfg the right interface? I presume this is i440fx specific? How
>> does q35 handle this?
>
> No, there is no i440fx or q35 in that case. There are discrete chips
> and wiring on an undefined ISA motherboard. As Seabios depends on a
> writable E&F-segments (maybe only on E, still need to find out) for a
> certain period, we need to invent a pv channel (probably via fw_cfg) to
> provide the necessary control knob.
I see, I thought this was primarily for shadowing. But it's a
SeaBIOS-ism. fw_cfg is the right answer.
Regards,
Anthony Liguori
>
>> Presumably there's a second window for the BIOS
>> mapping. There's got to be some way to do shadowing of it I would
>> think.
>
> Not sure what you mean here. This is only about shadowing the top 128K
> of the BIOS into the E/F-segment and providing a write-enable knob for it.
>
> Jan
>
> --
> Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
> Corporate Competence Center Embedded Linux
