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SubjectRe: [PATCH 11/18] KVM: MMU: Add infrastructure for two-level page walker
On Mon, Mar 08, 2010 at 11:37:22AM +0200, Avi Kivity wrote:
> 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@amd.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.

Ok, doing the translation in kvm_read_guest is certainly the more
generic approach. I already fixed a bug related to loading l2 pdptr
pointers. Doing the translation in kvm_read_guest makes the code a lot
nicer.

Joerg




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