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

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Message-ID: <4BD6DF7C.1090203@redhat.com>
Date:	Tue, 27 Apr 2010 15:58:36 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Joerg Roedel <joerg.roedel@....com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 16/22] KVM: MMU: Track page fault data in struct vcpu

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@....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

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