Re: [PATCH v3 2/4] libxc: support of linear p2m list for migration of pv-domains

[Juergen Gross <jgross@suse.com>]

On 06/01/16 16:40, Wei Liu wrote:
> On Wed, Dec 16, 2015 at 10:24:18AM +0100, Juergen Gross wrote:
> [...]
>> @@ -698,21 +868,19 @@ static int normalise_pagetable(struct xc_sr_context *ctx, const uint64_t *src,
>>              /* 32bit guests can only use the first 4 entries of their L3 tables.
>>               * All other are potentially used by Xen. */
>>              xen_first = 4;
>> -            xen_last = 512;
>> +            xen_last = 511;
> 
> Is this a bug fix in its own right?

Hmm, bug fix is too much. It is a harmonization with the change below
using macros to set xen_last to 511 at maximum. In fact it doesn't
matter, because xen_last is used in:

   if ( i >= xen_first && i <= xen_last )

with i being in the range from 0 to 511.


Juergen

> 
> Wei.
> 
>>              break;
>>  
>>          case XEN_DOMCTL_PFINFO_L2TAB:
>>              /* It is hard to spot Xen mappings in a 32bit guest's L2.  Most
>>               * are normal but only a few will have Xen mappings.
>> -             *
>> -             * 428 = (HYPERVISOR_VIRT_START_PAE >> L2_PAGETABLE_SHIFT_PAE)&0x1ff
>> -             *
>> -             * ...which is conveniently unavailable to us in a 64bit build.
>>               */
>> -            if ( pte_to_frame(src[428]) == ctx->x86_pv.compat_m2p_mfn0 )
>> +            i = (HYPERVISOR_VIRT_START_X86_32 >> L2_PAGETABLE_SHIFT_PAE) & 511;
>> +            if ( pte_to_frame(src[i]) == ctx->x86_pv.compat_m2p_mfn0 )
>>              {
>> -                xen_first = 428;
>> -                xen_last = 512;
>> +                xen_first = i;
>> +                xen_last = (HYPERVISOR_VIRT_END_X86_32 >>
>> +                            L2_PAGETABLE_SHIFT_PAE) & 511;
>>              }
>>              break;
>>          }
>> -- 
>> 2.6.2
>>
> 
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