Re: [Xen-users] DomU sees only 512MB RAM with PCI-passthrough

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Dec 13, 2012 at 12:16:37PM +0000, David Vrabel wrote:
> On 13/12/12 11:57, Ian Campbell wrote:
> > On Thu, 2012-12-13 at 11:43 +0000, Christian Holpert wrote:
> >> Hello Ian,
> >>
> >> At 10:38 13.12.2012, you wrote:
> >>> On Wed, 2012-12-12 at 17:04 +0000, Christian Holpert wrote:
> >>>> Please tell me, if you need more logs.
> >>>
> >>> dmesg of the guest booting both with and without the pci device might be
> >>> interesting. So would the output of "xl -vvv create" in both cases.
> >>
> >> attached.
> > 
> > In the diff of the dmesg I see:
> >         --- dmesg_without_pci.log       2012-12-13 11:50:00.000000000 +0000
> >         +++ dmesg_with_pci.log  2012-12-13 11:50:00.000000000 +0000
> >         @@ -1,72 +1,92 @@
> >          Reserving virtual address space above 0xf5800000
> >          Linux version 3.6.6-gentoo (root@xen) (gcc version 4.5.4 (Gentoo 
> > 4.5.4 p1.0, pie-0.4.7) ) #1 SMP Tue Nov 13 17:47:58 CET 2012
> >          ACPI in unprivileged domain disabled
> >         +Freeing 20000-80000 pfn range: 393216 pages freed
> >         +1-1 mapping on 20000->100000
> >         +Released 393216 pages of unused memory
> >         +Set 917504 page(s) to 1-1 mapping
> >          e820: BIOS-provided physical RAM map:
> >          Xen: [mem 0x0000000000000000-0x000000000009ffff] usable
> >          Xen: [mem 0x00000000000a0000-0x00000000000fffff] reserved
> >         -Xen: [mem 0x0000000000100000-0x000000007fffffff] usable
> >         +Xen: [mem 0x0000000000100000-0x000000001fffffff] usable
> >         +Xen: [mem 0x0000000020000000-0x00000000201fffff] reserved
> >         +Xen: [mem 0x0000000020200000-0x0000000040003fff] unusable
> >         +Xen: [mem 0x0000000040004000-0x0000000040004fff] reserved
> >         +Xen: [mem 0x0000000040005000-0x00000000d9cbefff] unusable
> >         +Xen: [mem 0x00000000d9cbf000-0x00000000da285fff] reserved
> >         +Xen: [mem 0x00000000da286000-0x00000000da505fff] ACPI NVS
> >         +Xen: [mem 0x00000000da506000-0x00000000da50afff] ACPI data
> >         +Xen: [mem 0x00000000da50b000-0x00000000da54dfff] ACPI NVS
> >         +Xen: [mem 0x00000000da54e000-0x00000000dad55fff] unusable
> >         +Xen: [mem 0x00000000dad56000-0x00000000daff1fff] reserved
> >         +Xen: [mem 0x00000000daff2000-0x00000000daffffff] unusable
> >         +Xen: [mem 0x00000000db800000-0x00000000df9fffff] reserved
> >         +Xen: [mem 0x00000000f8000000-0x00000000fbffffff] reserved
> >         +Xen: [mem 0x00000000fec00000-0x00000000fec00fff] reserved
> >         +Xen: [mem 0x00000000fed00000-0x00000000fed03fff] reserved
> >         +Xen: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved
> >         +Xen: [mem 0x00000000fee00000-0x00000000fee00fff] reserved
> >         +Xen: [mem 0x00000000ff000000-0x00000000ffffffff] reserved
> >          NX (Execute Disable) protection: active
> >          MPS support code is not built-in.
> >          Using acpi=off or acpi=noirq or pci=noacpi may have problem
> >          DMI not present or invalid.
> >          e820: update [mem 0x00000000-0x0000ffff] usable ==> reserved
> >          e820: remove [mem 0x000a0000-0x000fffff] usable
> >         -e820: last_pfn = 0x80000 max_arch_pfn = 0x1000000
> >         +e820: last_pfn = 0x20000 max_arch_pfn = 0x1000000
> 
> I think the kernel has done the correct thing with the supplied e820 map.
> 
> > On the libxl side with pci I also see:
> >         +libxl: debug: libxl_pci.c:85:libxl__create_pci_backend: Creating 
> > pci backend
> >         +libxl: debug: libxl_x86.c:82:e820_sanitize: Memory: 2097152kB End 
> > of RAM: 0x20000 (PFN) Delta: 1572864kB, PCI start: 524288kB (0x20000 PFN), 
> > Balloon 0kB
> >         +
> >         +libxl: debug: libxl_x86.c:201:e820_sanitize: : [0 -> 20000] RAM
> 
> This is the 512 MiB limit here, so I think the bug is in libxl.

Correct.
> 
> Why has it placed the PCI window at 512 MiB anyway?  3 GiB would be more
> conventional.

It "copies" what the E820 is and tries it best to sanitize it.

But it looks to have missed the "RAM" chunks in from the 0->3GB.

However, it should have made the 'Balloon' be much much bigger value.
Something is off there. What type of machine is this? An Intel DQSW..something?

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