Hello, I'm trying to boot a NetBSD PVH dom0 on Xen 4.20. The same NetBSD kernel works fine with Xen 4.18
The boot options are:
menu=Boot netbsd-current PVH Xen420:dev hd0f:;load /netbsd-PVH console=com0
root=wd0f; multiboot /xen420-debug.gz dom0_mem=1024M console=com1
com1=38400,8n1 loglvl=all guest_loglvl=all gnttab_max_nr_frames=64
sync_console=1 dom0=pvh
and the full log from serial console is attached.
With 4.20 the boot fails with:
(XEN) *** Serial input to DOM0 (type 'CTRL-a' three times to switch input)
(XEN) Freed 664kB init memory
(XEN) d0v0 Triple fault - invoking HVM shutdown action 1
(XEN) *** Dumping Dom0 vcpu#0 state: ***
(XEN) ----[ Xen-4.20.2-pre_20250821nb0 x86_64 debug=y Tainted: C ]----
(XEN) CPU: 7
(XEN) RIP: 0008:[<000000000020e268>]
(XEN) RFLAGS: 0000000000010006 CONTEXT: hvm guest (d0v0)
(XEN) rax: 000000002024c003 rbx: 000000000020e260 rcx: 00000000000dfeb7
(XEN) rdx: 0000000000100000 rsi: 0000000000103000 rdi: 000000000013e000
(XEN) rbp: 0000000080000000 rsp: 00000000014002e4 r8: 0000000000000000
(XEN) r9: 0000000000000000 r10: 0000000000000000 r11: 0000000000000000
(XEN) r12: 0000000000000000 r13: 0000000000000000 r14: 0000000000000000
(XEN) r15: 0000000000000000 cr0: 0000000000000011 cr4: 0000000000000000
(XEN) cr3: 0000000000000000 cr2: 0000000000000000
(XEN) fsb: 0000000000000000 gsb: 0000000000000000 gss: 0000000000000000
(XEN) ds: 0010 es: 0010 fs: 0000 gs: 0000 ss: 0010 cs: 0008
because of the triple fault the RIP above doens't point to the code.
I tracked it down to this code:
cmpl $0,%ecx ; /* zero-sized? */ \
je 2f ; \
pushl %ebp ; \
movl RELOC(nox_flag),%ebp ; \
1: movl %ebp,(PDE_SIZE-4)(%ebx) ; /* upper 32 bits: NX */ \
movl %eax,(%ebx) ; /* store phys addr */ \
addl $PDE_SIZE,%ebx ; /* next PTE/PDE */ \
addl $PAGE_SIZE,%eax ; /* next phys page */ \
loop 1b ; \
popl %ebp ; \
2: ;
there are others pushl/popl before so I don't think that's the problem
(in fact the exact same fragment is called just before with different
inputs and it doesn't fault). So the culprit it probably the write to (%ebx),
which would be 0x20e260
This is in the range:
(XEN) [0000000000100000, 0000000040068e77] (usable)
so I can't see why this would be a problem.
Any idea, including how to debug this further, welcome
thanks
--
Manuel Bouyer <bou...@antioche.eu.org>
NetBSD: 26 ans d'experience feront toujours la difference
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4.20.log.gz
Description: Binary data
