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<20240315105902.160047-9-carlo.nonato@minervasys.tech> <3f615066-a792-493f-ba33-7667a6557c23@xen.org> <9e0f7ff3-5457-41e4-a1e4-bf75804fb900@xen.org> <255be735-f9fe-4e39-a24e-2f6aff91acc5@suse.com> <3427132d-9458-4447-b667-d2ef3c1f0569@suse.com> From: Jan Beulich Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC 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26.03.2024 17:39, Carlo Nonato wrote: > On Mon, Mar 25, 2024 at 8:19 AM Jan Beulich wrote: >> On 22.03.2024 16:07, Carlo Nonato wrote: >>> On Thu, Mar 21, 2024 at 5:23 PM Jan Beulich wrote: >>>> On 21.03.2024 17:10, Julien Grall wrote: >>>>> On 21/03/2024 16:07, Julien Grall wrote: >>>>>> On 15/03/2024 10:58, Carlo Nonato wrote: >>>>>>> PGC_static and PGC_extra needs to be preserved when assigning a page. >>>>>>> Define a new macro that groups those flags and use it instead of or'ing >>>>>>> every time. >>>>>>> >>>>>>> To make preserved flags even more meaningful, they are kept also when >>>>>>> switching state in mark_page_free(). >>>>>>> >>>>>>> Signed-off-by: Carlo Nonato >>>>>> >>>>>> This patch is introducing a regression in OSStest (and possibly gitlab?): >>>>>> >>>>>> Mar 21 12:00:29.533676 (XEN) pg[0] MFN 2211c5 c=0x2c00000000000000 o=0 >>>>>> v=0xe40000010007ffff t=0x24 >>>>>> Mar 21 12:00:42.829785 (XEN) Xen BUG at common/page_alloc.c:1033 >>>>>> Mar 21 12:00:42.829829 (XEN) ----[ Xen-4.19-unstable x86_64 debug=y >>>>>> Not tainted ]---- >>>>>> Mar 21 12:00:42.829857 (XEN) CPU: 12 >>>>>> Mar 21 12:00:42.841571 (XEN) RIP: e008:[] >>>>>> common/page_alloc.c#alloc_heap_pages+0x37f/0x6e2 >>>>>> Mar 21 12:00:42.841609 (XEN) RFLAGS: 0000000000010282 CONTEXT: >>>>>> hypervisor (d0v8) >>>>>> Mar 21 12:00:42.853654 (XEN) rax: ffff83023e3ed06c rbx: >>>>>> 000000000007ffff rcx: 0000000000000028 >>>>>> Mar 21 12:00:42.853689 (XEN) rdx: ffff83047bec7fff rsi: >>>>>> ffff83023e3ea3e8 rdi: ffff83023e3ea3e0 >>>>>> Mar 21 12:00:42.865657 (XEN) rbp: ffff83047bec7c10 rsp: >>>>>> ffff83047bec7b98 r8: 0000000000000000 >>>>>> Mar 21 12:00:42.877647 (XEN) r9: 0000000000000001 r10: >>>>>> 000000000000000c r11: 0000000000000010 >>>>>> Mar 21 12:00:42.877682 (XEN) r12: 0000000000000001 r13: >>>>>> 0000000000000000 r14: ffff82e0044238a0 >>>>>> Mar 21 12:00:42.889652 (XEN) r15: 0000000000000000 cr0: >>>>>> 0000000080050033 cr4: 0000000000372660 >>>>>> Mar 21 12:00:42.901651 (XEN) cr3: 000000046fe34000 cr2: 00007fb72757610b >>>>>> Mar 21 12:00:42.901685 (XEN) fsb: 00007fb726def380 gsb: >>>>>> ffff88801f200000 gss: 0000000000000000 >>>>>> Mar 21 12:00:42.913646 (XEN) ds: 0000 es: 0000 fs: 0000 gs: 0000 >>>>>> ss: e010 cs: e008 >>>>>> Mar 21 12:00:42.913680 (XEN) Xen code around >>>>>> (common/page_alloc.c#alloc_heap_pages+0x37f/0x6e2): >>>>>> Mar 21 12:00:42.925645 (XEN) d1 1c 00 e8 ad dd 02 00 <0f> 0b 48 85 c9 >>>>>> 79 36 0f 0b 41 89 cd 48 c7 47 f0 >>>>>> Mar 21 12:00:42.937649 (XEN) Xen stack trace from rsp=ffff83047bec7b98: >>>>>> Mar 21 12:00:42.937683 (XEN) 0000000000000024 000000007bec7c20 >>>>>> 0000000000000001 ffff83046ccda000 >>>>>> Mar 21 12:00:42.949653 (XEN) ffff82e000000021 0000000000000016 >>>>>> 0000000000000000 0000000000000000 >>>>>> Mar 21 12:00:42.949687 (XEN) 0000000000000000 0000000000000000 >>>>>> 0000000000000028 0000000000000021 >>>>>> Mar 21 12:00:42.961652 (XEN) ffff83046ccda000 0000000000000000 >>>>>> 00007d2000000000 ffff83047bec7c48 >>>>>> Mar 21 12:00:42.961687 (XEN) ffff82d0402302ff ffff83046ccda000 >>>>>> 0000000000000100 0000000000000000 >>>>>> Mar 21 12:00:42.973655 (XEN) ffff82d0405f0080 00007d2000000000 >>>>>> ffff83047bec7c80 ffff82d0402f626c >>>>>> Mar 21 12:00:42.985656 (XEN) ffff83046ccda000 ffff83046ccda640 >>>>>> 0000000000000000 0000000000000000 >>>>>> Mar 21 12:00:42.985690 (XEN) ffff83046ccda220 ffff83047bec7cb0 >>>>>> ffff82d0402f65a0 ffff83046ccda000 >>>>>> Mar 21 12:00:42.997662 (XEN) 0000000000000000 0000000000000000 >>>>>> 0000000000000000 ffff83047bec7cc0 >>>>>> Mar 21 12:00:43.009660 (XEN) ffff82d040311f8a ffff83047bec7ce0 >>>>>> ffff82d0402bd543 ffff83046ccda000 >>>>>> Mar 21 12:00:43.009695 (XEN) ffff83047bec7dc8 ffff83047bec7d08 >>>>>> ffff82d04032c524 ffff83046ccda000 >>>>>> Mar 21 12:00:43.021653 (XEN) ffff83047bec7dc8 0000000000000002 >>>>>> ffff83047bec7d58 ffff82d040206750 >>>>>> Mar 21 12:00:43.033642 (XEN) 0000000000000000 ffff82d040233fe5 >>>>>> ffff83047bec7d48 0000000000000000 >>>>>> Mar 21 12:00:43.033678 (XEN) 0000000000000002 00007fb72767f010 >>>>>> ffff82d0405e9120 0000000000000001 >>>>>> Mar 21 12:00:43.045654 (XEN) ffff83047bec7e70 ffff82d040240728 >>>>>> 0000000000000007 ffff83023e3b3000 >>>>>> Mar 21 12:00:43.045690 (XEN) 0000000000000246 ffff83023e2efa90 >>>>>> ffff83023e38e000 ffff83023e2efb40 >>>>>> Mar 21 12:00:43.057609 (XEN) 0000000000000007 ffff83023e3afb80 >>>>>> 0000000000000206 ffff83047bec7dc0 >>>>>> Mar 21 12:00:43.069662 (XEN) 0000001600000001 000000000000ffff >>>>>> e75aaa8d0000000c ac0d6d864e487f62 >>>>>> Mar 21 12:00:43.069697 (XEN) 000000037fa48d76 0000000200000000 >>>>>> ffffffff000003ff 00000002ffffffff >>>>>> Mar 21 12:00:43.081647 (XEN) 0000000000000000 00000000000001ff >>>>>> 0000000000000000 0000000000000000 >>>>>> Mar 21 12:00:43.093646 (XEN) Xen call trace: >>>>>> Mar 21 12:00:43.093677 (XEN) [] R >>>>>> common/page_alloc.c#alloc_heap_pages+0x37f/0x6e2 >>>>>> Mar 21 12:00:43.093705 (XEN) [] F >>>>>> alloc_domheap_pages+0x17d/0x1e4 >>>>>> Mar 21 12:00:43.105652 (XEN) [] F >>>>>> hap_set_allocation+0x73/0x23c >>>>>> Mar 21 12:00:43.105685 (XEN) [] F >>>>>> hap_enable+0x138/0x33c >>>>>> Mar 21 12:00:43.117646 (XEN) [] F >>>>>> paging_enable+0x2d/0x45 >>>>>> Mar 21 12:00:43.117679 (XEN) [] F >>>>>> hvm_domain_initialise+0x185/0x428 >>>>>> Mar 21 12:00:43.129652 (XEN) [] F >>>>>> arch_domain_create+0x3e7/0x4c1 >>>>>> Mar 21 12:00:43.129687 (XEN) [] F >>>>>> domain_create+0x4cc/0x7e2 >>>>>> Mar 21 12:00:43.141665 (XEN) [] F >>>>>> do_domctl+0x1850/0x192d >>>>>> Mar 21 12:00:43.141699 (XEN) [] F >>>>>> pv_hypercall+0x617/0x6b5 >>>>>> Mar 21 12:00:43.153656 (XEN) [] F >>>>>> lstar_enter+0x13a/0x140 >>>>>> Mar 21 12:00:43.153689 (XEN) >>>>>> Mar 21 12:00:43.153711 (XEN) >>>>>> Mar 21 12:00:43.153731 (XEN) **************************************** >>>>>> Mar 21 12:00:43.165647 (XEN) Panic on CPU 12: >>>>>> Mar 21 12:00:43.165678 (XEN) Xen BUG at common/page_alloc.c:1033 >>>>>> Mar 21 12:00:43.165703 (XEN) **************************************** >>>>>> Mar 21 12:00:43.177633 (XEN) >>>>>> Mar 21 12:00:43.177662 (XEN) Manual reset required ('noreboot' specified) >>>>>> >>>>>> The code around the BUG is: >>>>>> >>>>>> /* Reference count must continuously be zero for free pages. */ >>>>>> if ( (pg[i].count_info & ~PGC_need_scrub) != PGC_state_free ) >>>>>> { >>>>>> printk(XENLOG_ERR >>>>>> "pg[%u] MFN %"PRI_mfn" c=%#lx o=%u v=%#lx t=%#x\n", >>>>>> i, mfn_x(page_to_mfn(pg + i)), >>>>>> pg[i].count_info, pg[i].v.free.order, >>>>>> pg[i].u.free.val, pg[i].tlbflush_timestamp); >>>>>> BUG(); >>>>>> } >>>>>> >>>>>> Now that you are preserving some flags, you also want to modify the >>>>>> condition. I haven't checked the rest of the code, so there might be >>>>>> some adjustments necessary. >>>>> >>>>> Actually maybe the condition should not be adjusted. I think it would be >>>>> wrong if a free pages has the flag PGC_extra set. Any thoughts? >>>> >>>> I agree, yet I'm inclined to say PGC_extra should have been cleared >>>> before trying to free the page. >>> >>> So what to do now? Should I drop this commit? >> >> No, we need to get to the root of the issue. Since osstest has hit it quite >> easily as it seems, I'm somewhat surprised you didn't hit it in your testing. >> In any event, as per my earlier reply, my present guess is that your change >> has merely uncovered a previously latent issue elsewhere. > > Ok, what about removing PGC_extra in free_heap_pages() before the > mark_page_free() call? Question is: How would you justify such a change? IOW I'm not convinced (yet) this wants doing there. Jan