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Re: [PATCH] xen: Move NX handling to a dedicated place

To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Date: Thu, 22 Jan 2026 15:09:20 +0100

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Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, "Daniel P . Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>, Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>, Julian Vetter <julian.vetter@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx

Delivery-date: Thu, 22 Jan 2026 14:09:32 +0000

List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

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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