Re: [Xen-ia64-devel] [Q] about assign_domain_page_replace

[Akio Takebe <takebe_akio@xxxxxxxxxxxxxx>]

Hi, Isaku

Thank you for your reply.

>"mfn != old_mfn" itself isn't a bug of Xen VMM.
>It should be okay from the hypervisor point of view.
>In both case (== and !=), Xen VMM should continue to work finely.
>domain_put_page() makes mfn_to_page(old_mfn)->count_info = 0 and
>frees the page.
No, get_page() is not called for the page.
So, after domain_put_page(), the page->count_info=-1.
>
>On the other hand, "pte_mem(old_pte) == true" is a bad sign
>from the dom0 point of view. (the current domain is dom0, right?)
>domain shouldn't assign new page to pseudo physicall address
>which page is already assigned to. I.e. usually pte_mem(old_pte) is false.
>Dom0 seems to work badly.
>
Thanks, I understand.

>
>> So if I destroy the domain, hypervisor panic like the below.
>> 
>> (XEN) Xen BUG at mm.c:233
>> (XEN) FIXME: implement ia64 dump_execution_state() 
>> (XEN) **************************************** 
>> (XEN) Panic on CPU 1: 
>> (XEN) Xen BUG at mm.c:233                      
>> (XEN) **************************************** 
>> (XEN)                                          
>> (XEN) Reboot in five seconds...
>
>mm.c:233 isn't BUG_ON() in my tree. Does it correspond to mm.c:232 in
>xen-ia64-unstable.hg of c/s 15162:0cf6b75423e9?
>If so, the pte entry is already updated to point to mfn so that
>old_mfn shouldn't be involved.
>
I used a little old cset.
But I also tried c/s 15162:0cf6b75423e9, and the results is below.

(XEN) domain.c:536: arch_domain_create:536 domain 1 pervcpu_vhpt 1              
 
(XEN) tlb_track.c:69: allocated 256 num_entries 256 num_free 256                
 
(XEN) tlb_track.c:115: hash 0xf000004084af0000 hash_size 512                    
 
(XEN) regionreg.c:193: ### domain f0000000040f8080: rid=80000-c0000 mp_rid=2000 
 
(XEN) domain.c:573: arch_domain_create: domain=f0000000040f8080                 
 
(XEN) vcpu.c:1059:d1 vcpu_get_lrr0: Unmasked interrupts unsupported             
 
(XEN) vcpu.c:1068:d1 vcpu_get_lrr1: Unmasked interrupts unsupported             
 
(XEN) domain.c:943:d1 Domain set shared_info_va to 0xfffffffffff00000           
 
(XEN) mm.c:698:d1 vcpu 0 iip 0xa0000001004fbbc0: bad I/O port access d 1 0x64   
 
(XEN) Xen BUG at mm.c:232                                                       
 
(XEN) FIXME: implement ia64 dump_execution_state()                              
 
(XEN)                                                                           
 
(XEN) ****************************************                                  
 
(XEN) Panic on CPU 1:                                                           
 
(XEN) Xen BUG at mm.c:232                                                       
 
(XEN) ****************************************                                  
 
(XEN)                                                                           
 
(XEN) Reboot in five seconds... 

I have seen the issue on only PRIMEQUEST.

>Could you elaborate on details?
>- paravirtualized domain or domVTi?
it's paravirtualized domain.

>- What is the activity to trigger assign_domain_page_replace() with
>  pte_mem(old_pte) true?
I'll check it.

Best Regards,

Akio Takebe


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