From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH 4/7] KVM: MMU: document mmio page fault Date: Wed, 19 Jun 2013 20:59:58 +0800 Message-ID: <51C1AB4E.5020402@linux.vnet.ibm.com> References: <1371632965-20077-1-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <1371632965-20077-5-git-send-email-xiaoguangrong@linux.vnet.ibm.com> <51C19FC6.9020001@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: gleb@redhat.com, avi.kivity@gmail.com, mtosatti@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org To: Paolo Bonzini Return-path: In-Reply-To: <51C19FC6.9020001@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 06/19/2013 08:10 PM, Paolo Bonzini wrote: > Il 19/06/2013 11:09, Xiao Guangrong ha scritto: >> Document it to Documentation/virtual/kvm/mmu.txt >> >> Signed-off-by: Xiao Guangrong >> --- >> Documentation/virtual/kvm/mmu.txt | 11 +++++++++-- >> 1 file changed, 9 insertions(+), 2 deletions(-) >> >> diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt >> index 5a6b2e2..4fb442b 100644 >> --- a/Documentation/virtual/kvm/mmu.txt >> +++ b/Documentation/virtual/kvm/mmu.txt >> @@ -270,14 +270,21 @@ 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, walk shadow page table to get the last spte where the mmio >> + information is stored and cache the information to vcpu->arch.mmio_gva, >> + vcpu->arch.access and vcpu->arch.mmio_gfn then call the emulator to emulate >> + the instruction who will get the benefit from the cached mmio info > > + - 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 Nice. > >> - 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 bits on the spte > > Added "(see callers of kvm_mmu_set_mmio_spte_mask)". Not really related, but > just came to my mind: perhaps we can have a section on A/D bits too. It is useful i think. Will do it.