Re: Xen-4.4-rc2 - Some Nested Virt testing

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 21/01/2014 18:12, Andrew Cooper wrote:
> Hello,
>
> I have been giving nested virt a try, and have my first bug to report. 
> This is still ongoing, and is by no means complete yet.
>
> Setup:
> Each reference to XenServer is a trunk XenServer based on 4.4-rc2
>
> Single Intel Haswell SDP (Grantley platform):
> Native hypervisor: XenServer
>
> Two L1 guests:
>   XenServer (running with EPT)
>   XenServer (running with shadow)
>
>
> When attempting to create an L2 EPT HVM domain under an L1 shadow
> domain, the L1 shadow domain is killed with:
>
> (XEN) <vm_launch_fail> error code 7
> (XEN) domain_crash_sync called from vmcs.c:1293
> (XEN) Domain 16 (vcpu#3) crashed on cpu#2:
> (XEN) ----[ Xen-4.4.0-xs82349-d  x86_64  debug=y  Not tainted ]----
> (XEN) CPU:    2
> (XEN) RIP:    0000:[<0000000000000000>]
> (XEN) RFLAGS: 0000000000000002   CONTEXT: hvm guest
> (XEN) rax: 0000000000000000   rbx: ffff83043cad8000   rcx: ffff83043cadff80
> (XEN) rdx: ffff82d0801d6ea0   rsi: 0000000000000000   rdi: ffff82d0801e2e8c
> (XEN) rbp: ffff82d080105680   rsp: 0000000000000000   r8:  ffff830064100000
> (XEN) r9:  ffff82d0801056ee   r10: ffff83043cadff70   r11: 0000000000000000
> (XEN) r12: ffff83043cadff50   r13: ffff830441e42000   r14: ffff830064100000
> (XEN) r15: ffff82d080189425   cr0: 0000000000000039   cr4: 0000000000002050
> (XEN) cr3: 0000000000000000   cr2: 0000000000000000
> (XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: 0000   cs: 0000

I suppose it is worth adding that `xl dmesg` from the L1 shadow
XenServer shows:

(XEN) VMX: Supported advanced features:
(XEN)  - APIC MMIO access virtualisation
(XEN)  - APIC TPR shadow
(XEN)  - Extended Page Tables (EPT)
(XEN)  - Virtual-Processor Identifiers (VPID)
(XEN)  - MSR direct-access bitmap
(XEN)  - Unrestricted Guest
(XEN) HVM: ASIDs enabled.
(XEN) HVM: VMX enabled
(XEN) HVM: Hardware Assisted Paging (HAP) detected
(XEN) HVM: HAP page sizes: 4kB, 2MB, 1GB
(XEN) Brought up 4 CPUs

Which indicates that EPT is available even in a shadow L1 domain.  I
can't think of a technical reason why it wouldn't work.

>
>
> I am continuing experiments with different VMs under each L1 hypervisor,
> to see what else breaks.
>
> ~Andrew
>
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