Re: [Xen-devel] [PATCH] Allow PV superpages to work with live migration

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 20:10 +0100 on 17 May (1274127046), Dave McCracken wrote:
> 
> PV superpages currently do not work with live migration.  They fall over dead 
> when the shadow page table is enabled for dirty tracking.  The HVM support 
> for 
> superpages in this code has been tested and found to work just fine for PV 
> superpages.  This patch modifies the test macro to allow the code to work 
> with 
> PV superpages.

It rather overshoots. :)  This enables PSE even for HVM guests which
have explicitly disabled it.   I think you want

    return (is_hvm_vcpu(v) ? (GUEST_PAGING_LEVELS != 2
                              || !hvm_paging_enabled(v)
                              || (v->arch.hvm_vcpu.guest_cr[4] & X86_CR4_PSE))
                           : opt_allow_hugepage);

Cheers,

Tim.

Content-Description: xen-unstable-smigrate-1.patch
> --- xen-unstable//xen/include/asm-x86/guest_pt.h      2010-04-19 
> 09:23:24.000000000 -0500
> +++ xen-hmigrate//xen/include/asm-x86/guest_pt.h      2010-05-17 
> 14:00:34.000000000 -0500
> @@ -186,10 +186,11 @@ guest_supports_superpages(struct vcpu *v
>      /* The _PAGE_PSE bit must be honoured in HVM guests, whenever
>       * CR4.PSE is set or the guest is in PAE or long mode. 
>       * It's also used in the dummy PT for vcpus with CR4.PG cleared. */
> -    return (is_hvm_vcpu(v) && 
> -            (GUEST_PAGING_LEVELS != 2 
> -             || !hvm_paging_enabled(v)
> -             || (v->arch.hvm_vcpu.guest_cr[4] & X86_CR4_PSE)));
> +    return (opt_allow_hugepage ||
> +         (is_hvm_vcpu(v) && 
> +          (GUEST_PAGING_LEVELS != 2 
> +           || !hvm_paging_enabled(v)
> +           || (v->arch.hvm_vcpu.guest_cr[4] & X86_CR4_PSE))));
>  }
>  
>  static inline int

Content-Description: ATT00001..txt
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-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, XenServer Engineering
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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