linux-kernel - Re: [PATCH 11/18] KVM: MMU: Add infrastructure for two-level page walker

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Message-ID: <4B94C552.30604@redhat.com>
Date:	Mon, 08 Mar 2010 11:37:22 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Joerg Roedel <joerg.roedel@....com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	Alexander Graf <agraf@...e.de>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/18] KVM: MMU: Add infrastructure for two-level page
 walker

On 03/03/2010 09:12 PM, Joerg Roedel wrote:
> This patch introduces a mmu-callback to translate gpa
> addresses in the walk_addr code. This is later used to
> translate l2_gpa addresses into l1_gpa addresses.
>
> Signed-off-by: Joerg Roedel<joerg.roedel@....com>
> ---
>   arch/x86/include/asm/kvm_host.h |    1 +
>   arch/x86/kvm/mmu.c              |    7 +++++++
>   arch/x86/kvm/paging_tmpl.h      |   19 +++++++++++++++++++
>   include/linux/kvm_host.h        |    5 +++++
>   4 files changed, 32 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index c0b5576..76c8b5f 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -250,6 +250,7 @@ struct kvm_mmu {
>   	void (*free)(struct kvm_vcpu *vcpu);
>   	gpa_t (*gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t gva, u32 access,
>   			    u32 *error);
> +	gpa_t (*translate_gpa)(struct kvm_vcpu *vcpu, gpa_t gpa, u32 *error);
>   	void (*prefetch_page)(struct kvm_vcpu *vcpu,
>   			      struct kvm_mmu_page *page);
>   	int (*sync_page)(struct kvm_vcpu *vcpu,
>    

I think placing this here means we will miss a few translations, namely 
when we do a physical access (say, reading PDPTEs or similar).

We need to do this on the level of kvm_read_guest() so we capture 
physical accesses:

kvm_read_guest_virt
   -> walk_addr
      -> kvm_read_guest_tdp
          -> kvm_read_guest_virt
             -> walk_addr
                 -> kvm_read_guest_tdp
                      -> kvm_read_guest

Of course, not all accesses will use kvm_read_guest_tdp; for example 
kvmclock accesses should still go untranslated.

-- 
error compiling committee.c: too many arguments to function

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