On Wed, May 18, 2016 at 05:52:29PM +0300, Marcel Apfelbaum wrote: > On 05/18/2016 05:42 PM, Michael S. Tsirkin wrote: > >On Wed, May 18, 2016 at 04:31:46PM +0200, Igor Mammedov wrote: > >>On Wed, 18 May 2016 17:12:09 +0300 > >>Marcel Apfelbaum <mar...@redhat.com> wrote: > >> > >>>On 05/18/2016 05:11 PM, Michael S. Tsirkin wrote: > >>>>On Wed, May 18, 2016 at 03:59:29PM +0200, Igor Mammedov wrote: > >>>>>On Sun, 15 May 2016 22:23:32 +0300 > >>>>>Marcel Apfelbaum <mar...@redhat.com> wrote: > >>>>> > >>>>>>Using the firmware assigned MMIO ranges for 64-bit PCI window > >>>>>>leads to zero space for hot-plugging PCI devices over 4G. > >>>>>> > >>>>>>PC machines can use the whole CPU addressable range after > >>>>>>the space reserved for memory-hotplug. > >>>>>> > >>>>>>Signed-off-by: Marcel Apfelbaum <mar...@redhat.com> > >>>>>that patch also has side effect of unconditionally adding > >>>>>QWordMemory() resource in PCI0._CRS > >>>>>on all machine types with QEMU generated ACPI tables. > >>>>> > >>>>>Have you tested that it won't break boot of legacy OSes > >>>>>(XP, WS2003, old linux with 32bit kernel)? > >>>> > >>>>It's almost sure it break it. > >>>>Maybe you can check _REV in _CRS to work around this for XP. > >>> > >>>I'll try it. > >>but only after you check if just presence of QWord would crash XP, > >>so in case it doesn't crash we would keep _CRS simple static > >>structure. > >> > >>I very vaguely recall that XP ignored QWord in PCI0._CRS, > >>but it was long time ago so it won't hurt to recheck. > > > >I played with different guests (32 and 64 bit) > >at some point. > > > >Generally, windows tends to crash when CRS resources exceed the > >supported limits > >of physical memory (sometimes with weird off by one errors, > >e.g. win7 32 bit seems to survive with a 36 bit pci hole even though > >this means the max address is 2^37-1 which it can't address). > > > >This might depend on CPU as well. > > It seems QEMU returns 40-bit as CPU addressable bits, but I might got it > wrong. > > > > >Which makes me ask: why don't we fix this in BIOS? > >If you want it to allocate a large window, do it. > > I don't follow, BIOS can assign resources to PCI devices, but how to > specify a MMIO range for hot-plug? Add it to the CRS of the host-bridge, > right? > > Thanks, > Marcel > > [...]
Ah I forgot on PC there's no register for this. On Q35 there is. -- MST
