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From: Julien Grall <julien.grall@arm.com>
To: Benjamin Sanda <ben.sanda@dornerworks.com>,
	xen-devel@lists.xenproject.org
Cc: Keir Fraser <keir@xen.org>,
	Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	Dario Faggioli <dario.faggioli@citrix.com>,
	Tim Deegan <tim@xen.org>,
	George Dunlap <george.dunlap@citrix.com>,
	Jan Beulich <jbeulich@suse.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Paul Sujkov <psujkov@gmail.com>
Subject: Re: [PATCH 3/6] xentrace: P2M lookup suport for ARM platform
Date: Thu, 17 Mar 2016 16:21:27 +0000	[thread overview]
Message-ID: <56EAD987.6080204@arm.com> (raw)
In-Reply-To: <1458161499-15313-4-git-send-email-ben.sanda@dornerworks.com>

Hello Benjamin,

Thank you for the patch.

On 16/03/16 20:51, Benjamin Sanda wrote:
> From: bensanda <ben.sanda@dornerworks.com>
>
> Modified p2m_lookup() to provide support for xentrace on the ARM platform. Added check for DOMID_XEN which skips PFN to MFN translation. xentrace sends a MFN dirrectly when requesting DOMID_XEN, so no translation is needed. Also sets page memory type, p2m_type_t, to p2m_ram_rw to provide correct access.

A line in the commit message should not be longer than 72 characters.

>
> Signed-off-by: Benjamin Sanda <ben.sanda@dornerworks.com>
> ---
>   xen/arch/arm/p2m.c | 19 +++++++++++++++----
>   1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index a2a9c4b..2e7da43 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -228,10 +228,21 @@ paddr_t p2m_lookup(struct domain *d, paddr_t paddr, p2m_type_t *t)
>       paddr_t ret;
>       struct p2m_domain *p2m = &d->arch.p2m;
>
> -    spin_lock(&p2m->lock);
> -    ret = __p2m_lookup(d, paddr, t);
> -    spin_unlock(&p2m->lock);
> -
> +    /* Check for DOMID_XEN: If we are called with DOMID_XEN (from xentrace)

Multi-lines comment in Xen should be:

/*
  * Foo
  * Bar
  */

You can find the coding style in CODING_STYLE.

> +    then paddr is already a MFN and no translation is needed. We only set the
> +    page type as p2m_raw_rw and return the MFN directly */

DOMID_XEN is not specific to xentrace. It's a mechanism to share xenheap 
page to any guest.

xentrace is using directly an MFN because DOMID_XEN is considered as a 
PV guest on x86 (i.e MFN == GFN). And we don't have a such concept on ARM.

> +    if(DOMID_XEN != d->domain_id)


if ( d->domain_id != DOMID_XEN )

> +    {
> +        spin_lock(&p2m->lock);
> +        ret = __p2m_lookup(d, paddr, t);
> +        spin_unlock(&p2m->lock);
> +    }
> +    else
> +    {
> +        *t = p2m_ram_rw;

A DOMID_XEN page could be read only too. For instance, the meta-data of 
the trace buffer is read-only (see t_info), we don't want a domain to be 
able to overwrite them.

However, all the foreign page are mapped read-write. You will need to 
rework the code to map a foreign domain (see XENMAPSPACE_gmfn_foreign) 
to allow read-only foreign page (maybe by adding a new p2m_type_t?).

> +        ret = paddr;
> +    }
> +
>       return ret;
>   }
>
>

Regards,

-- 
Julien Grall

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  reply	other threads:[~2016-03-17 16:21 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-16 20:51 [PATCH 0/6] xentrace/xenalyze support on ARM Benjamin Sanda
2016-03-16 20:51 ` [PATCH 1/6] Flask: Support for ARM xentrace Benjamin Sanda
2016-03-17 14:56   ` Julien Grall
2016-03-17 15:03   ` Julien Grall
2016-03-25 19:27   ` Konrad Rzeszutek Wilk
2016-03-28 15:52     ` Ben Sanda
2016-03-16 20:51 ` [PATCH 2/6] xenalyze: Support for ARM platform Benjamin Sanda
2016-03-16 20:59   ` Andrew Cooper
2016-03-17 10:39     ` George Dunlap
2016-03-16 20:51 ` [PATCH 3/6] xentrace: P2M lookup suport " Benjamin Sanda
2016-03-17 16:21   ` Julien Grall [this message]
2016-03-28 18:55     ` Ben Sanda
2016-03-30 18:38       ` Julien Grall
2016-03-16 20:51 ` [PATCH 4/6] xentrace: ARM platform DOMID_XEN mapping support Benjamin Sanda
2016-03-17 15:53   ` Julien Grall
2016-03-16 20:51 ` [PATCH 5/6] xentrace: Trace buffer support for ARM platform Benjamin Sanda
2016-03-16 20:51 ` [PATCH 6/6] xentrace: ARM platform timestamp support Benjamin Sanda
2016-03-25 19:31   ` Konrad Rzeszutek Wilk
2016-03-31 16:38     ` Stefano Stabellini
2016-03-31 16:44       ` Ben Sanda
2016-04-01 13:05         ` Stefano Stabellini
2016-03-17 15:00 ` [PATCH 0/6] xentrace/xenalyze support on ARM Julien Grall
2016-03-17 16:50   ` Ben Sanda
2016-03-17 17:01     ` Julien Grall
2016-03-17 17:04       ` Ben Sanda
2016-03-18 17:12         ` Wei Liu
2016-03-17 17:23 ` George Dunlap

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