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

From: Julien Grall <julien.grall@arm.com>
To: Sergej Proskurin <proskurin@sec.in.tum.de>,
	xen-devel@lists.xenproject.org
Cc: Stefano Stabellini <sstabellini@kernel.org>
Subject: Re: [PATCH 10/18] arm/altp2m: Renamed and extended p2m_alloc_table.
Date: Mon, 4 Jul 2016 19:43:17 +0100	[thread overview]
Message-ID: <577AAE45.2020505@arm.com> (raw)
In-Reply-To: <20160704114605.10086-11-proskurin@sec.in.tum.de>

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.

> +            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,

-- 
Julien Grall

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