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KVM: MMU: document mmio page fault

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Document it to Documentation/virtual/kvm/mmu.txt

Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Xiao Guangrong 2013-06-19 17:09:22 +08:00 committed by Gleb Natapov
parent 0cbf8e437b
commit 67652ed343
1 changed files with 9 additions and 2 deletions
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Documentation/virtual/kvm/mmu.txt
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@ -272,14 +272,21 @@ This is the most complicated event. The cause of a page fault can be:
Handling a page fault is performed as follows:
- if the RSV bit of the error code is set, the page fault is caused by guest
accessing MMIO and cached MMIO information is available.
- walk shadow page table
- cache the information to vcpu->arch.mmio_gva, vcpu->arch.access and
vcpu->arch.mmio_gfn, and call the emulator
- if needed, walk the guest page tables to determine the guest translation
(gva->gpa or ngpa->gpa)
- if permissions are insufficient, reflect the fault back to the guest
- determine the host page
- if this is an mmio request, there is no host page; call the emulator
to emulate the instruction instead
- if this is an mmio request, there is no host page; cache the info to
vcpu->arch.mmio_gva, vcpu->arch.access and vcpu->arch.mmio_gfn
- walk the shadow page table to find the spte for the translation,
instantiating missing intermediate page tables as necessary
- If this is an mmio request, cache the mmio info to the spte and set some
reserved bit on the spte (see callers of kvm_mmu_set_mmio_spte_mask)
- try to unsynchronize the page
- if successful, we can let the guest continue and modify the gpte
- emulate the instruction