Re: stable-4.18: reliably crash network driver domain by squeezing free_memory

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

On 28/11/2024 3:31 pm, James Dingwall wrote:
> Hi,
>
> We have reproducible issue with the current HEAD of the stable-4.18 branch
> which crashes a network driver domain and on some hardware subsequently
> results in a dom0 crash.
>
> `xl info` reports: free_memory : 39961, configuring a guest with
> memory = 39800 and starting it gives the log as below.  This is intel
> hardware so if I've followed the code correctly I think this leads through
> to intel_iommu_map_page() from drivers/passthrough/vtd/iommu.c.
>
> The expectation is that we can safely allocate up to free_memory for a
> guest without any issue.  Is there any extra logging we could enable to
> gain more information?

For this, you really should CC the x86 maintainers, or it stands a
chance of getting missed.

Do you have the complete serial log including boot and eventual crash ?

-12 is -ENOMEM so something is wonky, and while dom2 is definitely dead
at this point, Xen ought to be able to unwind cleanly and not take down
dom0 too.

~Andrew

>
> Thanks,
> James
>
>
> (XEN) d2: IOMMU mapping dfn afdf79 to mfn afdf79 failed: -12
> (XEN) domain_crash called from drivers/passthrough/iommu.c:366
> (XEN) Domain 2 (vcpu#1) crashed on cpu#3:
> (XEN) ----[ Xen-4.18.4-pre  x86_64  debug=y  Not tainted ]----
> (XEN) CPU:    3
> (XEN) RIP:    e033:[<ffffffff8220128c>]
> (XEN) RFLAGS: 0000000000000282   EM: 0   CONTEXT: pv guest (d2v1)
> (XEN) rax: 0000000000000014   rbx: ffffc90041361000   rcx: ffffffff8220128c
> (XEN) rdx: 0000000000000001   rsi: ffffc9004136b018   rdi: 0000000000000000
> (XEN) rbp: ffffc900400e0e18   rsp: ffffc900400e0dc8   r8:  0000000000000000
> (XEN) r9:  0000000000000000   r10: 0000000000000000   r11: 0000000000000282
> (XEN) r12: 0000000000000001   r13: ffffc9004136b018   r14: ffffc90041361000
> (XEN) r15: 0000000000000000   cr0: 0000000080050033   cr4: 00000000003526e0
> (XEN) cr3: 0000000cb07c6000   cr2: 00005dc9ed4f6710
> (XEN) fsb: 000073436e0b9400   gsb: ffff888023100000   gss: 0000000000000000
> (XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: e02b   cs: e033
> (XEN) Guest stack trace from rsp=ffffc900400e0dc8:
> (XEN)    0000000000000000 0000000000000001 ffffffff81a94320 0000000000000000
> (XEN)    ffffc9004136e818 ffffc90041361000 0000000000000000 0000000000000001
> (XEN)    ffffc90041361000 0000000000000000 ffffc900400e0e58 ffffffffc0542f35
> (XEN)    0000000100000001 1332c17936eda000 ffffc90041361030 0000000000000000
> (XEN)    0000000000000040 ffffc90041361000 ffffc900400e0e88 ffffffffc05464ae
> (XEN)    ffffc90041361030 0000000000000000 ffffc900400e0eef 0000000000000040
> (XEN)    ffffc900400e0ec0 ffffffff81edef70 ffff888023135e40 000000000000012c
> (XEN)    ffffc900400e0ef8 ffffc90041361030 0000000000000000 ffffc900400e0f48
> (XEN)    ffffffff81edf551 ffffffff811b5c7f ffff888023136100 0000000100566b96
> (XEN)    0000000000000007 ffff888023131b60 ffffc900400e0ef8 ffffc900400e0ef8
> (XEN)    ffffc900400e0f08 ffffc900400e0f08 1332c17936eda000 0000000080000100
> (XEN)    0000000000000003 0000000000000008 0000000000000004 ffffffff834060d8
> (XEN)    ffffc900400e0fb8 ffffffff8110a198 ffff888023134200 0040010000000001
> (XEN)    ffff888004798000 0000000100566b96 000000000000000a ffffc90000000003
> (XEN)    ffffffff81a9f77e ffffc9004000b788 0000000000000000 0000000000000000
> (XEN)    0000000000000000 0000000000000000 ffffc900400e0fd8 ffffffff8110a4e9
> (XEN)    ffffc9004000b788 0000000000000000 ffffc900400e0fe8 ffffffff8110a84e
> (XEN)    ffffc9004000b778 ffffffff821ffd0a ffffc9004000b760
> (XEN)     Fault while accessing guest memory.
> (XEN) common/memory.c:278:d0v2 Could not allocate order=18 extent: id=24 memflags=0xc0 (0 of 1)
> ...repeated
> (XEN) common/memory.c:278:d0v2 Could not allocate order=9 extent: id=24 memflags=0xc0 (3 of 4)
> (XEN) common/memory.c:278:d0v2 Could not allocate order=9 extent: id=24 memflags=0xc0 (0 of 4)
> ...repeated
>
>
>
>
> decoding the symbols from the crashed driver domain:
>
> vcpu0:
> rip: ffffffff8220128c
> flags: 00001282 i s nz
> rsp: ffffc90040003dc8
> rax: 0000000000000000 rcx: ffffffff8220128c rdx: deadbeefdeadf00d
> rbx: ffffc90040358680 rsi: deadbeefdeadf00d rdi: deadbeefdeadf00d
> rbp: ffffc90040003e18 r8: 0000000000000000 r9: 0000000000000000
> r10: 0000000000000000 r11: 0000000000000282 r12: 0000000000000001
> r13: ffffc90040362698 r14: ffffc90040358680 r15: 0000000000000000
> cs: e033 ss: e02b ds: 0000 es: 0000
> fs: 0000 @ 0000000000000000
> gs: 0000 @ ffff888103c00000/0000000000000000
> Code (instr addr ffffffff8220128c)
> cc cc cc cc cc cc cc cc cc 51 41 53 48 c7 c0 14 00 00 00 0f 05 <41> 5b 59 c3 cc cc cc cc cc cc cc
>
>
> Stack:
> 0000000000000000 0000000000000001 ffffffff81a942a0 0000000000000000
> ffffc90040365e98 ffffc90040358680 0000000000000000 0000000000000001
> ffffc90040358680 0000000000000000 ffffc90040003e58 ffffffffc05a6f35
> 0000000200000001 2acc1e6e51961900 ffffc900403586b0 0000000000000000
> 0000000000000040 ffffc90040358680 ffffc90040003e88 ffffffffc05aa4ae
>
> Call Trace:
> [<ffffffff8220128c>] <--  xen_hypercall_grant_table_op+0xc
> ffffc90040003dd8: [<ffffffff81a942a0>]  gnttab_map_refs+0x30
> ffffc90040003e20: [<ffffffffc05a6f35>]  
> ffffc90040003e60: [<ffffffffc05aa4ae>]  
> ffffc90040003e90: [<ffffffff81edede0>]  __napi_poll+0x30
> ffffc90040003ec8: [<ffffffff81edf3c1>]  net_rx_action+0x181
> ffffc90040003ed0: [<ffffffff811b5c7f>]  generic_handle_irq+0x1f
> ffffc90040003f40: [<ffffffff834060d8>]  
> ffffc90040003f50: [<ffffffff8110a198>]  handle_softirqs+0xd8
> ffffc90040003f68: [<ffffffff8340fcc0>]  
> ffffc90040003f88: [<ffffffff81a9f6fe>]  evtchn_fifo_handle_events+0xe
> ffffc90040003f90: [<ffffffff83403cc8>]  
> ffffc90040003fc0: [<ffffffff8110a4e9>]  __irq_exit_rcu+0xd9
> ffffc90040003fc8: [<ffffffff83403cc8>]  
> ffffc90040003fe0: [<ffffffff8110a84e>]  irq_exit_rcu+0xe
> ffffc90040003fe8: [<ffffffff83403cb8>]  
> ffffc90040003ff0: [<ffffffff821ffd0a>]  xen_pv_evtchn_do_upcall+0xaa
> ffffc90040003ff8: [<ffffffff83403ca0>]  
>
> vcpu1:
> rip: ffffffff822013ac
> flags: 00001246 i z p
> rsp: ffffc900400a3e60
> rax: 0000000000000000 rcx: ffffffff822013ac rdx: 0000000000000000
> rbx: 0000000000000000 rsi: deadbeefdeadf00d rdi: deadbeefdeadf00d
> rbp: ffffc900400a3e78 r8: 0000000000000000 r9: 0000000000000000
> r10: 0000000000000000 r11: 0000000000000246 r12: ffff8881003b8000
> r13: 0000000000000000 r14: 0000000000000000 r15: 0000000000000000
> cs: e033 ss: e02b ds: 002b es: 002b
> fs: 0000 @ 0000000000000000
> gs: 0000 @ ffff888103d00000/0000000000000000
> Code (instr addr ffffffff822013ac)
> cc cc cc cc cc cc cc cc cc 51 41 53 48 c7 c0 1d 00 00 00 0f 05 <41> 5b 59 c3 cc cc cc cc cc cc cc
>
>
> Stack:
> 0000000000000000 0000000000000000 ffffffff82200060 ffffc900400a3e88
> ffffffff82209629 ffffc900400a3e98 ffffffff822096f9 ffffc900400a3ea8
> ffffffff822099cc ffffc900400a3ee8 ffffffff8117bf53 0000000000000001
> ac54db278c0d3c00 0000000000000001 ffff8881003b8000 0000000000000001
> 0000000000000000 ffffc900400a3f08 ffffffff8117c027 000000000000008f
>
> Call Trace:
> [<ffffffff822013ac>] <--  xen_hypercall_sched_op+0xc
> ffffc900400a3e70: [<ffffffff82200060>]  xen_safe_halt+0x10
> ffffc900400a3e80: [<ffffffff82209629>]  default_idle+0x9
> ffffc900400a3e90: [<ffffffff822096f9>]  arch_cpu_idle+0x9
> ffffc900400a3ea0: [<ffffffff822099cc>]  default_idle_call+0x2c
> ffffc900400a3eb0: [<ffffffff8117bf53>]  cpuidle_idle_call+0x153
> ffffc900400a3ef0: [<ffffffff8117c027>]  do_idle+0x87
> ffffc900400a3f10: [<ffffffff8117c2ba>]  cpu_startup_entry+0x2a
> ffffc900400a3f28: [<ffffffff8104bb51>]  cpu_bringup_and_idle+0xa1
> ffffc900400a3f50: [<ffffffff81052565>]  asm_cpu_bringup_and_idle+0x5
>
>