Re: performance with guests running 2.4 kernels (specifically RHEL3)

["David S. Ahern" <daahern@cisco.com>]

What is the rip (GUEST_RIP) value in the VMEXIT trace output? Is that the
current instruction pointer for the guest?

I take it the virt in the PAGE_FAULT trace output is the virtual address the
guest was referencing when the page fault occurred. What I don't understand (one
of many things really) is what the 0xfffb63b0 corresponds to in the guest. Any
ideas?

Also, the expensive page fault occurs on errorcode = 0x0000000b (PAGE_FAULT
trace data). What does the 4th bit in 0xb mean? bit 0 set means
PFERR_PRESENT_MASK is set, and bit 1 means PT_WRITABLE_MASK. What is bit 3?

david


David S. Ahern wrote:
> 
> Avi Kivity wrote:
>> Ah!  The flood detector is not seeing the access through the
>> kmap_atomic() pte, because that access has gone through the emulator. 
>> last_updated_pte_accessed(vcpu) will never return true.
>>
>> Can you verify that last_updated_pte_accessed(vcpu) indeed always
>> returns false?
>>
> 
> It returns both true and false. I added a tracer to kvm_mmu_pte_write() to dump
> the rc of last_updated_pte_accessed(vcpu). ie.,
> 	pte_access = last_updated_pte_accessed(vcpu);
>         KVMTRACE_1D(PTE_ACCESS, vcpu, (u32) pte_access, handler);
> 
> A sample:
> 
> (+    4488)  VMEXIT       [ exitcode = 0x00000000, rip = 0x00000000 c016104a ]
> (+       0)  PAGE_FAULT   [ errorcode = 0x0000000b, virt = 0x00000000 fffb63b0 ]
> (+    2480)  PAGE_FAULT1  [ write_count = 0 ]
> (+     424)  PAGE_FAULT2  [ level = 2 metaphysical = 0 access 0x00000007 ]
> (+   51672)  PAGE_FAULT3
> (+     472)  PAGE_FAULT4
> (+     704)  PAGE_FAULT5  [ shadow_ent = 0x80000001 2dfb5043 ]
> (+    1496)  VMENTRY
> (+    4568)  VMEXIT       [ exitcode = 0x00000000, rip = 0x00000000 c01610e7 ]
> (+       0)  PAGE_FAULT   [ errorcode = 0x00000003, virt = 0x00000000 c0009db4 ]
> (+    2352)  PAGE_FAULT1  [ write_count = 0 ]
> (+     728)  PAGE_FAULT5  [ shadow_ent = 0x00000001 91409041 ]
> (+       0)  PTE_WRITE    [ gpa = 0x00000000 00009db4 gpte = 0x00000000 41fb5363 ]
> (+       0)  PTE_ACCESS   [ pte_access = 1 ]
> (+    6864)  VMENTRY
> (+    3896)  VMEXIT       [ exitcode = 0x00000000, rip = 0x00000000 c01610ee ]
> (+       0)  PAGE_FAULT   [ errorcode = 0x00000003, virt = 0x00000000 c0009db0 ]
> (+    2376)  PAGE_FAULT1  [ write_count = 1 ]
> (+     720)  PAGE_FAULT5  [ shadow_ent = 0x00000001 91409041 ]
> (+       0)  PTE_WRITE    [ gpa = 0x00000000 00009db0 gpte = 0x00000000 00000000 ]
> (+       0)  PTE_ACCESS   [ pte_access = 0 ]
> (+   12344)  VMENTRY
> (+    4688)  VMEXIT       [ exitcode = 0x00000000, rip = 0x00000000 c016127c ]
> (+       0)  PAGE_FAULT   [ errorcode = 0x00000003, virt = 0x00000000 c0009db4 ]
> (+    2416)  PAGE_FAULT1  [ write_count = 2 ]
> (+     792)  PAGE_FAULT5  [ shadow_ent = 0x00000001 91409043 ]
> (+    1128)  VMENTRY
> (+    4512)  VMEXIT       [ exitcode = 0x00000000, rip = 0x00000000 c016104a ]
> (+       0)  PAGE_FAULT   [ errorcode = 0x0000000b, virt = 0x00000000 fffb63b0 ]
> (+    2448)  PAGE_FAULT1  [ write_count = 0 ]
> (+     448)  PAGE_FAULT2  [ level = 2 metaphysical = 0 access 0x00000007 ]
> (+   51520)  PAGE_FAULT3
> (+     432)  PAGE_FAULT4
> (+     696)  PAGE_FAULT5  [ shadow_ent = 0x80000001 2df5a043 ]
> (+    1480)  VMENTRY
> 
> 
> david
> 

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