Re: [Xen-users] Xen - Linux PV on HVM drivers

["Fajar A. Nugraha" <list@xxxxxxxxx>]

On Tue, Jun 21, 2011 at 1:37 PM, Alex <alex@xxxxxxxxxx> wrote:
> Hi Guys,
>
> Is there a way to get Xen PV-on-HVM drivers for Linux HVM guests working on
> ubuntu server 11.04 x86_64?

It works. Sort of.

> I am using Ubuntu server on my Xen HVM VPS. It would be nice to use the PV
> drivers for HVM to take advantage of performance improvements.
>
> I am running a custom kernel 2.6.39.1 and have enabled Xen support in the
> kernel (under "Processor type and features" -> "Paravirtualized guest
> support" -> "Xen guest support"
>
> However it appears this is not working, it's not using the PV-on-HVM drivers
> (still using the QEMU detected stuff).
>
> Quote:
> ------
> root@srv:/usr/src/linux# dmesg | grep -i xen
>
> Linux version 2.6.39.1-customserver-xen (root@xxxxxxxxxxxxxxxx) (gcc version
> 4.5.2 (Ubuntu/Linaro 4.5.2-8ubuntu4) ) #1 SMP PREEMPT Sun Jun 19 16:41:16
> EST 2011
> DMI: Xen HVM domU, BIOS 3.4.3 01/22/2011
> ACPI: RSDP 00000000000ea020 00024 (v02 Xen)
> ACPI: XSDT 00000000fc006060 00034 (v01 Xen HVM 00000000 HVML 00000000)
> ACPI: FACP 00000000fc005ee0 000F4 (v04 Xen HVM 00000000 HVML 00000000)
> ACPI: DSDT 00000000fc002c40 0321F (v02 Xen HVM 00000000 INTL 20090220)
> ACPI: APIC 00000000fc005fe0 00080 (v02 Xen HVM 00000000 HVML 00000000)
> XENFS: not registering filesystem on non-xen platform

The trick is you need to make sure that xen-platform-pci is loaded
BEFORE xen-blkfront loaded. This makes natty's linux-image-virtual
unusable for PVonHVM since xen-blkfront is compiled in, while
xen-platform-pci is compiled as module. Using linux-image-server, and
adding these entrie, make it work:

# cat /etc/initramfs-tools/modules
xen-platform-pci
xen-blkfront

Here's the result:

# dmesg | egrep -i "xen|blkfront"
[    0.000000] DMI: Xen HVM domU, BIOS 4.0.1-1.pv_ops.el5 01/13/2011
[    0.000000] Hypervisor detected: Xen HVM
[    0.000000] Xen version 4.0.
[    0.000000] Xen Platform PCI: I/O protocol version 1
[    0.000000] Netfront and the Xen platform PCI driver have been
compiled for this kernel: unplug emulated NICs.
[    0.000000] Blkfront and the Xen platform PCI driver have been
compiled for this kernel: unplug emulated disks.
[    0.000000] ACPI: RSDP 00000000000ea020 00024 (v02    Xen)
[    0.000000] ACPI: XSDT 00000000fc012cb0 00034 (v01    Xen      HVM
00000000 HVML 00000000)
[    0.000000] ACPI: FACP 00000000fc012ad0 000F4 (v04    Xen      HVM
00000000 HVML 00000000)
[    0.000000] ACPI: DSDT 00000000fc002c40 0FE0B (v02    Xen      HVM
00000000 INTL 20090123)
[    0.000000] ACPI: APIC 00000000fc012bd0 000D8 (v02    Xen      HVM
00000000 HVML 00000000)
[    0.000000] Booting paravirtualized kernel on Xen
[    0.000000] Xen HVM callback vector for event delivery is enabled
[    0.210018] Xen: using vcpuop timer interface
[    0.210029] installing Xen timer for CPU 0
[    0.020000] installing Xen timer for CPU 1
[    0.020000] installing Xen timer for CPU 2
[    0.020000] installing Xen timer for CPU 3
[    0.020000] installing Xen timer for CPU 4
[    0.020000] installing Xen timer for CPU 5
[    1.526585] Switching to clocksource xen
[    4.861230] xen-platform-pci 0000:00:03.0: PCI INT A -> GSI 28
(level, low) -> IRQ 28
[    5.006193] blkfront device/vbd/51712 num-ring-pages 1 nr_ents 32.
[    5.013080] blkfront: xvda: barriers enabled
[    5.038129] blkfront device/vbd/51728 num-ring-pages 1 nr_ents 32.
[    5.075300] blkfront: xvdb: barriers enabled
[   15.673938] Initialising Xen virtual ethernet driver.
[   22.996610] blkfront: xvda: empty write barrier op failed
[   22.996618] blkfront: xvda: barriers disabled


# lsmod | grep xen
xen_netfront           26568  0
xen_blkfront           22122  5
xenbus_probe_frontend    13194  2 xen_netfront,xen_blkfront,[permanent]
xen_platform_pci       12836  0 [permanent]

If you use custom kernel, either compile them all as builtin, or make
sure xen-platform-pci is loaded.

-- 
Fajar

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