On 2011-03-10 10:47, Gleb Natapov wrote: > On Wed, Mar 09, 2011 at 08:51:23PM -0800, Jordan Justen wrote: >> Hi all, >> >> I have documented a simple flash-like device which I think could be >> useful for qemu/kvm in some cases. (Particularly for allowing >> persistent UEFI non-volatile variables.) >> >> http://wiki.qemu.org/Features/System_Flash >> >> Let me know if you have any suggestions or concerns. >> > > Two things. First You suggest to replace -bios with -flash. This will > make firmware upgrade painful process that will have to be performed > from inside the guest since the same flash image will contain both > firmware and whatever data was stored on a flash which presumably you > want to reuse after upgrading a firmware. My suggestion is to extend > -bios option like this: > > -bios bios.bin,flash=flash.bin,flash_base=addr > > flash.bin will be mapped at address flash_base, or, if flash_base is not > present, just below bios.bin.
...or define -flash in a way that allows mapping the bios image as an overlay to the otherwise guest-managed flash image. > > Second. I asked how flash is programmed because interfaces like CFI > where you write into flash memory address range to issue commands cannot > be emulated efficiently in KVM. KVM supports either regular memory slots > or IO memory, but in your proposal the same memory behaves as IO on > write and regular memory on read. Better idea would be to present > non-volatile flash as ISA virtio device. Should be simple to implement. Why not enhancing KVM memory slots to support direct read access while writes are trapped and forwarded to a user space device model? Virtio means that you have to patch the guest (which might be something else than flexible Linux...). Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
