On 10/20/17 08:55, Gerd Hoffmann wrote: > Hi, > >>> commit message says: >>> >>> <quote> >>> It turns out that some 32 bit windows guests crash >>> if 64 bit PCI hole size is >2G. >>> </quote> >>> >>> Why this suddenly isn't a problem any more? >>> >> >> I suppose it is, so we need a way to turn it "off". > > Or have machine types behave differently, i.e. give q35 a large 64bit > hole and leave pc as-is.
*If* we make it dependent on machine types at all, then please also make it versioned for Q35. > > Devices with that large bars are most likely pci express anyway ... > >> This is how I started, however Eduardo and (and maybe Michael ?) >> where against letting the upper management software to deal with >> such a low low level detail. They simply can't take such a decision. >> This is why the property you mentioned is not ever linked >> in code anywhere! It is simply not implemented and not used. > > Makes sense. > > BTW: Is it safe to just assume 40 bits physical is going to work? My > workstation: > > model name : Intel(R) Core(TM) i7-7700K CPU @ 4.20GHz > address sizes : 39 bits physical, 48 bits virtual > > Does this imply ept is limited 39 bits physical too? Very good point to raise; "39 bits physical" on your workstation *does* imply that EPT is limited exactly the same way. I had run into this very problem while working on 64GB+ RAM enablement in OVMF. (Back then my laptop had: "address sizes : 36 bits physical, 48 bits virtual".) Thanks, Laszlo
