From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@linaro.org>
Subject: Re: [PATCH v6 01/11] arch,
 arm: domain build: let dom0 access I/O memory of mapped devices
Date: Tue, 29 Apr 2014 13:37:21 +0100
Message-ID: <535F9D01.6000907@linaro.org>
References: <1398087904-16594-1-git-send-email-avanzini.arianna@gmail.com>
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To: Arianna Avanzini <avanzini.arianna@gmail.com>
Cc: julien.grall@citrix.com, paolo.valente@unimore.it, keir@xen.org, stefano.stabellini@eu.citrix.com, tim@xen.org, dario.faggioli@citrix.com, Ian.Jackson@eu.citrix.com, xen-devel@lists.xen.org, Ian.Campbell@eu.citrix.com, etrudeau@broadcom.com, JBeulich@suse.com, viktor.kleinik@globallogic.com
List-Id: xen-devel@lists.xenproject.org

Hi Arianna,

On 04/21/2014 02:44 PM, Arianna Avanzini wrote:
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index 187e071..1802b6e 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -11,6 +11,7 @@
>  #include <xen/device_tree.h>
>  #include <xen/libfdt/libfdt.h>
>  #include <xen/guest_access.h>
> +#include <xen/iocap.h>
>  #include <asm/setup.h>
>  #include <asm/platform.h>
>  #include <asm/psci.h>
> @@ -740,6 +741,16 @@ static int map_device(struct domain *d, const struct dt_device_node *dev)
>          DPRINT("addr %u = 0x%"PRIx64" - 0x%"PRIx64"\n",
>                 i, addr, addr + size - 1);
>  
> +        res = iomem_permit_access(d, paddr_to_pfn(addr & PAGE_MASK),
> +                                  paddr_to_pfn(PAGE_ALIGN(addr + size - 1)));
> +        if ( res )
> +        {
> +            printk(XENLOG_ERR "Unable to permit to dom%d access to"
> +                   " 0x%"PRIx64" - 0x%"PRIx64"\n",
> +                   d->domain_id,
> +                   addr & PAGE_MASK, PAGE_ALIGN(addr + size) - 1);
> +            return res;
> +        }
>          res = map_mmio_regions(d, addr & PAGE_MASK,
>                                 PAGE_ALIGN(addr + size) - 1,
>                                 addr & PAGE_MASK);
> 

I though a bit more about this patch. If the device is disabled (i.e
status="disabled"), Xen doesn't call map_device.
Futhermore, in your use case (e.g with iomem=) you might want to map
memory that is not describe to the device tree.

I would either:
	1) give a full access to the I/O range
	2) give a full access to the I/O range except on the RAM region

IHMO, the second solution might be better but I don't know if it's easy
to implement it.

Any thoughts?

Regards,

-- 
Julien Grall