Re: [Xen-devel] [PATCH 10/18] arm/altp2m: Renamed and extended p2m_alloc_table.

[Sergej Proskurin <proskurin@xxxxxxxxxxxxx>]

Hello Julien,


On 07/04/2016 08:43 PM, Julien Grall wrote:
> Hello Sergej,
>
> On 04/07/16 12:45, Sergej Proskurin wrote:
>> +int p2m_table_init(struct domain *d)
>> +{
>> +    int i = 0;
>> +    int rc = -ENOMEM;
>> +    struct p2m_domain *p2m = p2m_get_hostp2m(d);
>> +
>> +    spin_lock(&p2m->lock);
>> +
>> +    rc = p2m_alloc_table(p2m);
>> +    if ( rc != 0 )
>> +        goto out;
>> +
>> +    d->arch.vttbr = d->arch.p2m.vttbr.vttbr;
>> +
>> +    /*
>> +     * Make sure that all TLBs corresponding to the new VMID are
>> flushed
>> +     * before using it.
>>        */
>>       flush_tlb_domain(d);
>>
>>       spin_unlock(&p2m->lock);
>>
>> -    return 0;
>> +    if ( hvm_altp2m_supported() )
>> +    {
>> +        /* Init alternate p2m data */
>> +        for ( i = 0; i < MAX_ALTP2M; i++ )
>> +        {
>> +            d->arch.altp2m_vttbr[i] = INVALID_MFN;
>> +            rc = p2m_alloc_table(d->arch.altp2m_p2m[i]);
>
> Why do we need to allocate all the altp2m root page tables at the
> creation of the domain? This is wasting up to 80KB (2-root page for 10
> altp2m) per domain even if it may not be used at all by the domain.
>

As previously discussed in patch #05, I will change this behavior in a
way that altp2m views will be allocated at run time only when they are
needed. Thank you.

>> +            if ( rc != 0 )
>> +                goto out;
>> +        }
>> +
>> +        d->arch.altp2m_active = 0;
>> +    }
>> +
>> +out:
>> +    return rc;
>>   }
>>
>>   #define MAX_VMID 256
>> diff --git a/xen/include/asm-arm/p2m.h b/xen/include/asm-arm/p2m.h
>> index 783db5c..451b097 100644
>> --- a/xen/include/asm-arm/p2m.h
>> +++ b/xen/include/asm-arm/p2m.h
>> @@ -171,7 +171,7 @@ int relinquish_p2m_mapping(struct domain *d);
>>    *
>>    * Returns 0 for success or -errno.
>>    */
>> -int p2m_alloc_table(struct domain *d);
>> +int p2m_table_init(struct domain *d);
>>
>>   /* Context switch */
>>   void p2m_save_state(struct vcpu *p);
>>
>
> Regards,
>

Best,
~Sergej

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