Re: [Xen-devel] 15142:78389dbb08bb and domain state

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

Yeah, that's a nasty one. I committed an alternative fix, which I think is
clearer, as c/s 16401. Please give it a spin.

I'll also queue it for 3.1.3.

 -- Keir

On 19/11/07 10:19, "John Levon" <levon@xxxxxxxxxxxxxxxxx> wrote:

> On Fri, Nov 16, 2007 at 12:01:38AM +0000, Keir Fraser wrote:
> 
>> Reference counting for l4 pagetable entries happens in
>> get_page_from_l4e(),
> 
> The circular reference was a red herring - I was looking at Xen's own
> mapping in its private PTEs (d'oh).
> 
> However, I did notice that we leak a ref count per VCPU, which gave me a
> big clue. Changeset 13302:7c5eea5feebd from Jan added this code:
> 
> +#ifdef __x86_64__
> +            if ( pfn == pagetable_get_pfn(v->arch.guest_table_user) )
> +                v->arch.guest_table_user = pagetable_null();
> +#endif
> 
> Presumably for the benefit of compat guests where this is always true.
> 
> However, it can be true on native Solaris guests too - when we switch
> to the kernel L4 we also load it into _USER_BASEPTR.
> 
> The patch below fixes it for me (though I'm not positive it's correct).
> Assuming this or something like it is the right thing, that will still
> leave the 'xm list' problem, which I see with both Solaris and Linux
> domU's. Still looking at that.
> 
> cheers,
> john
> 
> # HG changeset patch
> # User john.levon@xxxxxxx
> # Date 1195467196 28800
> # Node ID b972585a05838dc3a622438299572423a7a8de8d
> # Parent  00c6696dcc8b17cd9ea2325f260899e489e262e0
> Fix VCPU pagetable cleanup
> 
> Solaris can have the same PT in guest_table and guest_table_user without
> it being a compat domain. Be more careful when cleaning up.
> 
> Signed-off-by: John Levon <john.levon@xxxxxxx>
> 
> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -1625,7 +1625,8 @@ static void vcpu_destroy_pagetables(stru
>          else
>              put_page_and_type(mfn_to_page(pfn));
>  #ifdef __x86_64__
> -        if ( pfn == pagetable_get_pfn(v->arch.guest_table_user) )
> +        if ( is_pv_32on64_vcpu(v) &&
> +      pfn == pagetable_get_pfn(v->arch.guest_table_user) )
>              v->arch.guest_table_user = pagetable_null();
>  #endif
>          v->arch.guest_table = pagetable_null();



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