On 22.01.2026 14:57, Andrew Cooper wrote:
> On 22/01/2026 1:48 pm, Julian Vetter wrote:
>> (XEN) Early fatal page fault at e008:ffff82d0403b38e0 
>> (cr2=0000000001100202, ec=0009)
>> (XEN) ----[ Xen-4.22-unstable  x86_64  debug=y  Not tainted ]----
>> (XEN) CPU:    0
>> (XEN) RIP:    e008:[<ffff82d0403b38e0>] memcmp+0x20/0x46
>> (XEN) RFLAGS: 0000000000010002   CONTEXT: hypervisor
>> (XEN) rax: 0000000000000000   rbx: 0000000001100000   rcx: 0000000000000000
>> (XEN) rdx: 0000000000000004   rsi: ffff82d0404a0d23   rdi: 0000000001100202
>> (XEN) rbp: ffff82d040497d88   rsp: ffff82d040497d78   r8:  0000000000000016
>> (XEN) r9:  ffff82d04061a180   r10: ffff82d04061a188   r11: 0000000000000010
>> (XEN) r12: 0000000001100000   r13: 0000000000000001   r14: ffff82d0404d2b80
>> (XEN) r15: ffff82d040462750   cr0: 0000000080050033   cr4: 00000000000000a0
>> (XEN) cr3: 00000000b5d0e000   cr2: 0000000001100202
>> (XEN) fsb: 0000000000000000   gsb: 0000000000000000   gss: 0000000000000000
>> (XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: 0000   cs: e008
>> (XEN) Xen code around <ffff82d0403b38e0> (memcmp+0x20/0x46):
>> (XEN)  0f 1f 84 00 00 00 00 00 <0f> b6 04 0f 44 0f b6 04 0e 44 29 c0 75 
>> 13 48 83
>> (XEN) Xen stack trace from rsp=ffff82d040497d78:
>> (XEN)    ffff82d040483f79 0000000000696630 ffff82d040497db0 ffff82d040483fd2
>> (XEN)    0000000000696630 ffff82d040200000 0000000000000001 ffff82d040497ef8
>> (XEN)    ffff82d04047c4ac 0000000000000000 0000000000000000 0000000000000000
>> (XEN)    ffff82d04062c6d8 0000000000000000 0000000000000000 0000000000000000
>> (XEN)    0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> (XEN)    0000000000000000 0000000000140000 0000000000000000 0000000000000001
>> (XEN)    0000000000000000 0000000000000000 ffff82d040497f08 ffff82d0404d2b80
>> (XEN)    0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> (XEN)    0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> (XEN)    0000000000000000 0000000800000000 000000010000006e 0000000000000003
>> (XEN)    00000000000002f8 0000000000000000 0000000000000000 0000000000000000
>> (XEN)    0000000099f30ba0 0000000099feeda7 0000000000000000 ffff82d040497fff
>> (XEN)    00000000b9cf3920 ffff82d0402043e8 0000000000000000 0000000000000000
>> (XEN)    0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> (XEN)    0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> (XEN)    0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> (XEN)    0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> (XEN)    0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> (XEN)    0000000000000000 0000e01000000000 0000000000000000 0000000000000000
>> (XEN)    00000000000000a0 0000000000000000 0000000000000000 0000000000000000
>> (XEN) Xen call trace:
>> (XEN)    [<ffff82d0403b38e0>] R memcmp+0x20/0x46
>> (XEN)    [<ffff82d040483f79>] S arch/x86/bzimage.c#bzimage_check+0x2e/0x73
>> (XEN)    [<ffff82d040483fd2>] F bzimage_headroom+0x14/0xa5
>> (XEN)    [<ffff82d04047c4ac>] F __start_xen+0x908/0x2452
>> (XEN)    [<ffff82d0402043e8>] F __high_start+0xb8/0xc0
>> (XEN)
>> (XEN) Pagetable walk from 0000000001100202:
>> (XEN)  L4[0x000] = 00000000b5c9d063 ffffffffffffffff
>> (XEN)
>> (XEN) ****************************************
>> (XEN) Panic on CPU 0:
>> (XEN) FATAL TRAP: vec 14, #PF[0009] IN INTERRUPT CONTEXT
>> (XEN) ****************************************
> 
> Huh, that means we have a bug in the pagewalk rendering.  It shouldn't
> give up like that.

Is it perhaps too early for mfn_valid() to return "true" for the page table
page in question?

Jan

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