On 22/07/2020 10.05, Janosch Frank wrote: > On 7/22/20 9:39 AM, Christian Borntraeger wrote: >> >> >> On 22.07.20 09:24, Janosch Frank wrote: >>> On 7/22/20 8:43 AM, Christian Borntraeger wrote: >>>> >>>> >>>> On 15.07.20 16:08, Janosch Frank wrote: >>>>> Normally they don't need to be set up before waiting for an interrupt >>>>> but are set up on boot. The BIOS however might overwrite the lowcore >>>>> (and hence the PSWs) when loading a blob into memory and therefore >>>>> needs to set up those PSWs more often. >>>> >>>> Now when I read the new comment this actually inidicates a bug. >>>> When do we restore the original content? If the loaded program >>>> does have interrupt handlers in the original image and relies on that >>>> then we are broken, no? >>> >>> I haven't seen references to a save/restore functionality for those >>> PSWs. And I also think it's not that easy to do because we have multiple >>> ways of loading data and if we want to print when loading we might end >>> up overwriting and then saving the written value for a later restore. >>> >>> I need to have a closer look at how virtio works, but wouldn't we have a >>> chicken - egg problem with IO interrupts for IO that writes the prefix? >>> >>> The BIOS often has "interesting" solutions to problems. >>> If you have a quick fix, be my guest and send it. If not I'd put it on >>> my todo list or let Stefan make it a proper dev item. >> >> Maybe a global fixup table in BIOS memory that restores all the memory that >> we messed with when we hand over control? Can you at least change the comment >> here to add a fixme? > > Sure
Hi Janosch! Did you ever send a new version of this patch with the FIXME added? I can't find it right now... Or shall I add a FIXME when picking this up? (If so, could you please suggest a text?) Thomas
