Re: [Qemu-devel] Use of flash for x86 BIOS

[Markus Armbruster]

Jordan Justen <address@hidden> writes:

> On Fri, Mar 22, 2013 at 12:48 PM, Markus Armbruster <address@hidden> wrote:
>> Jordan Justen <address@hidden> writes:
>>
>>> On Thu, Mar 21, 2013 at 12:45 AM, Markus Armbruster
>>> <address@hidden> wrote:
>>>> x86 maintainers may wish to *switch it off* until it's done fully and
>>>> properly, by setting "pc-sysfw" property "rom_only" to 1.
>>>
>>> This would completely disable the flash support.
>>
>> Unless the user enables it explicitly with something like "-global
>> pc-sysfw.rom_only=0".
>>
>>>                                                  At the time this
>>> feature was added, I think it was well understood that kvm would not
>>> support the flash mode, while plain qemu could. If it was not a
>>> show-stopper to integrating the feature originally, what has changed?
>>
>> Nothing changed, and that's the problem.
>>
>> Merging the feature was okay, I think.  Defaulting it to "on" with TCG
>> and "off" with KVM was a mistake, because that made enabling/disabling
>> KVM guest-visible (see item 2. below).  The default needs to be the same
>> both with and without KVM.  Since the thing still doesn't work with KVM,
>> the default needs to be "off".
>>
>> A possible explanation for making this mistake is that people assumed it
>> would soon work with KVM.  That turned out not to be the case.
>
> Given this can be overridden on the command line it does seem
> reasonable to disable it by default until KVM support is in place.

Sent, you're cc'ed.

> Slight off topic, does pc_q35 intend to support SPI flash at some
> point? SPI programming is at a different MMIO address from the flash,
> so it should be possible to support with qemu/kvm today.

No idea :)

> Are there any plans for Q35 to become the default qemu PC machine?

Unless I'm mistaken, that's the plan.