linux-kernel - Re: [PATCH 5/7] KVM: MMU: document fast page fault in

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Date:	Wed, 19 Jun 2013 14:13:55 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
CC:	gleb@...hat.com, avi.kivity@...il.com, mtosatti@...hat.com,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 5/7] KVM: MMU: document fast page fault in

Il 19/06/2013 11:09, Xiao Guangrong ha scritto:
> Document fast page fault to Documentation/virtual/kvm/mmu.txt
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
> ---
>  Documentation/virtual/kvm/mmu.txt | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt
> index 4fb442b..b5ce7dd 100644
> --- a/Documentation/virtual/kvm/mmu.txt
> +++ b/Documentation/virtual/kvm/mmu.txt
> @@ -275,6 +275,9 @@ Handling a page fault is performed as follows:
>     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 both P bit and R/W bit of error code are set, there has a chance to
> +   fast fix the page fault, please see the description of "Fast page fault" in
> +   Documentation/virtual/kvm/locking.txt

 - If both P bit and R/W bit of error code are set, this could possibly
   be handled as a "fast page fault" (fixed without taking the MMU lock).  See
   the description in Documentation/virtual/kvm/locking.txt.

Paolo

>   - 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
> 

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