Re: [Xen-devel] HVM support for e820_host (Was: Bug: Limitation of <=2GB RAM in domU persists with 4.3.0)

[Gordan Bobic <gordan@xxxxxxxxxx>]

On 09/05/2013 10:29 PM, Gordan Bobic wrote:
> On 09/05/2013 10:13 PM, Gordan Bobic wrote:
> > Right, finally got around to trying this with the latest patch.
> >
> > With e820_host=0 things work as before:
> >
> > (XEN) HVM3: BIOS map:
> > (XEN) HVM3:  f0000-fffff: Main BIOS
> > (XEN) HVM3: E820 table:
> > (XEN) HVM3:  [00]: 00000000:00000000 - 00000000:0009e000: RAM
> > (XEN) HVM3:  [01]: 00000000:0009e000 - 00000000:000a0000: RESERVED
> > (XEN) HVM3:  HOLE: 00000000:000a0000 - 00000000:000e0000
> > (XEN) HVM3:  [02]: 00000000:000e0000 - 00000000:00100000: RESERVED
> > (XEN) HVM3:  [03]: 00000000:00100000 - 00000000:e0000000: RAM
> > (XEN) HVM3:  HOLE: 00000000:e0000000 - 00000000:fc000000
> > (XEN) HVM3:  [04]: 00000000:fc000000 - 00000001:00000000: RESERVED
> > (XEN) HVM3:  [05]: 00000001:00000000 - 00000002:1f800000: RAM
> >
> >
> > I seem to be getting two different E820 table dumps with e820_host=1:
> >
> > (XEN) HVM1: BIOS map:
> > (XEN) HVM1:  f0000-fffff: Main BIOS
> > (XEN) HVM1: build_e820_table:91 got 8 op.nr_entries
> > (XEN) HVM1: E820 table:
> > (XEN) HVM1:  [00]: 00000000:00000000 - 00000000:3f790000: RAM
> > (XEN) HVM1:  [01]: 00000000:3f790000 - 00000000:3f79e000: ACPI
> > (XEN) HVM1:  [02]: 00000000:3f79e000 - 00000000:3f7d0000: NVS
> > (XEN) HVM1:  [03]: 00000000:3f7d0000 - 00000000:3f7e0000: RESERVED
> > (XEN) HVM1:  HOLE: 00000000:3f7e0000 - 00000000:3f7e7000
> > (XEN) HVM1:  [04]: 00000000:3f7e7000 - 00000000:40000000: RESERVED
> > (XEN) HVM1:  HOLE: 00000000:40000000 - 00000000:fee00000
> > (XEN) HVM1:  [05]: 00000000:fee00000 - 00000000:fee01000: RESERVED
> > (XEN) HVM1:  HOLE: 00000000:fee01000 - 00000000:ffc00000
> > (XEN) HVM1:  [06]: 00000000:ffc00000 - 00000001:00000000: RESERVED
> > (XEN) HVM1:  [07]: 00000001:00000000 - 00000001:68870000: RAM
> > (XEN) HVM1: E820 table:
> > (XEN) HVM1:  [00]: 00000000:00000000 - 00000000:0009e000: RAM
> > (XEN) HVM1:  [01]: 00000000:0009e000 - 00000000:000a0000: RESERVED
> > (XEN) HVM1:  HOLE: 00000000:000a0000 - 00000000:000e0000
> > (XEN) HVM1:  [02]: 00000000:000e0000 - 00000000:00100000: RESERVED
> > (XEN) HVM1:  [03]: 00000000:00100000 - 00000000:a7800000: RAM
> > (XEN) HVM1:  HOLE: 00000000:a7800000 - 00000000:fc000000
> > (XEN) HVM1:  [04]: 00000000:fc000000 - 00000001:00000000: RESERVED
> > (XEN) HVM1: Invoking ROMBIOS ...
> >
> > I cannot quite figure out what is going on here - these tables can't
> > both be true.
> >
> > Looking at the IOMEM on the host, the IOMEM begins at 0xa8000000 and
> > goes more or less contiguously up to 0xfec8b000.
> >
> > Looking at dmesg on domU, the e820 map more or less matches the second
> > dump above.
> >
> > So I guess that should work - the entire IOMEM area of the host is in
> > fact not mapped. But since I've passed 8GB of RAM to domU, shouldn't
> > there be another usable RAM area after 00000001:00000000 ?
> I should probably also mention that the domU does in fact see 8GB of
> RAM, so clearly it is working.
>
> The PCI IOMEM reservations on the host are:
> # lspci -vvv | grep Region | grep Memory | sed -e 's/.*Memory at //' | sort
> a8000000 (64-bit, prefetchable) [disabled] [size=128M]
> b0000000 (64-bit, prefetchable) [disabled] [size=64M]
> b4000000 (64-bit, prefetchable) [size=64M]
> b8000000 (64-bit, prefetchable) [size=128M]
> c0000000 (64-bit, prefetchable) [size=256M]
> d7efc000 (32-bit, non-prefetchable) [size=16K]
> d8000000 (64-bit, non-prefetchable) [size=64K]
> dc000000 (64-bit, non-prefetchable) [size=16K]
> f3df4000 (64-bit, non-prefetchable) [size=16K]
> f3df8000 (32-bit, non-prefetchable) [size=1K]
> f3dfa000 (32-bit, non-prefetchable) [size=1K]
> f3dfc000 (32-bit, non-prefetchable) [size=2K]
> f3dfe000 (64-bit, non-prefetchable) [size=256]
> f3edc000 (64-bit, non-prefetchable) [size=16K]
> f3fdc000 (64-bit, non-prefetchable) [size=16K]
> f4000000 (32-bit, non-prefetchable) [disabled] [size=32M]
> f7ffc000 (32-bit, non-prefetchable) [disabled] [size=16K]
> f8000000 (32-bit, non-prefetchable) [size=32M]
> fbcfc000 (32-bit, non-prefetchable) [size=16K]
> fbdfe000 (64-bit, non-prefetchable) [disabled] [size=8K]
> fbeef000 (32-bit, non-prefetchable) [size=2K]
> fbeefc00 (32-bit, non-prefetchable) [size=16]
> fec8a000 (32-bit, non-prefetchable) [size=4K]
>
>
> What is a little concerning is that my GPU in dom0 has it's IOMEM mapped at
> E0000000-E7FFFFFF
> E8000000-EBFFFFFF
> EC000000-EDFFFFFF
>
> Granted, this fits into a convenient hole in the host map
> 0xdc004000-0xf3df4000 but I cannot see that hole being listed as such in
> the xl dmesg E820 table dump. Is this _really_ working, or is it working
> by pure luck?
Just doing a bit of testing at the moment. I haven't had a crash yet (it 
would have happened by now, as things were before). But - I am 
definitely getting the sort of graphical glitching/corruption in 3D 
applications that I saw before when assigning > 2688MB of RAM to the 
domU. That implies that there is still some memory overwriting happening 
somewhere.
Aaand just as I was tying that - I've just had a crash. :'(

Back to the drawing board...

Gordan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel