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

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 ?


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