Re: [PATCH 16/22] KVM: MMU: Track page fault data in struct vcpu

Avi Kivity
2010-04-27T12:58:39Z

On 04/27/2010 01:38 PM, Joerg Roedel wrote:
> This patch introduces two fields in vcpu_arch for x86:
>
> * fault_address
> * fault_error_code
>
> This will be used to correctly propagate page faults back
> into the guest when we could have either an ordinary page
> fault or a nested page fault. In the case of a nested page
> fault the fault-address is different from the original
> address that should be walked. So we need to keep track
> about the real fault-address.
> We could also remove the current path of the error_code to
> the fault. But this change is too invasive and outside the
> scope of this patch set. It will be changed and tested
> seperatly.
>
> Signed-off-by: Joerg Roedel<joerg.roedel@amd.com>
> ---
> arch/x86/include/asm/kvm_host.h | 3 +++
> arch/x86/kvm/paging_tmpl.h | 4 ++++
> 2 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index d9dfc8c..8426870 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -298,6 +298,9 @@ struct kvm_vcpu_arch {
> /* Used for two dimensional paging emulation */
> struct kvm_mmu nested_mmu;
>
> + unsigned long fault_address;
>

Probably a problem on i386. How does npt handle faults when the guest
is using pae paging and the host (in our case the guest...) isn't? I
see it uses exit_info_2 for the address, which is a u64.

So we probably need to upgrade gva_t to a u64. Please send this as a
separate patch, and test on i386 hosts.

> + int fault_error_code;
>

unsigned.

Maybe put the two in a struct, easier to pass around.

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