From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@linaro.org>
Subject: Re: [PATCH v8 13/14] tools/libxl: explicitly grant
 access to needed I/O-memory ranges
Date: Sun, 25 May 2014 18:08:23 +0100
Message-ID: <53822387.2030101@linaro.org>
References: <1401015115-7610-1-git-send-email-avanzini.arianna@gmail.com>
	<1401015115-7610-14-git-send-email-avanzini.arianna@gmail.com>
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To: Arianna Avanzini <avanzini.arianna@gmail.com>, xen-devel@lists.xen.org
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, Ian.Campbell@eu.citrix.com, etrudeau@broadcom.com, JBeulich@suse.com, andrew.cooper3@citrix.com, viktor.kleinik@globallogic.com
List-Id: xen-devel@lists.xenproject.org

Hi Arianna,

On 25/05/14 11:51, Arianna Avanzini wrote:
> +
> +        /*
> +         * If VGA passthru is enabled by domain config, be sure that the
> +         * domain can access VGA-related iomem regions.
> +         */
> +        if (d_config->b_info.u.hvm.gfx_passthru.val) {
> +            uint64_t vga_iomem_start = 0xa0000 >> XC_PAGE_SHIFT;
> +            ret = xc_domain_iomem_permission(CTX->xch, domid,
> +                                             vga_iomem_start, 0x20, 1);
> +            if (ret < 0) {
> +                LOGE(ERROR,
> +                     "failed to give dom%d access to iomem range "
> +                     "%"PRIx64"-%"PRIx64" for VGA passthru",
> +                     domid, vga_iomem_start, (vga_iomem_start + 0x20 - 1));
> +                goto error_out;
> +            }
> +        }

IHMO, the guest doesn't need to have permission to this region. When 
QEMU ask to map this region to the guest, the hypercall will only check 
the permission on the domain where QEMU is running. Therefore, the 
permission should be given to the stubdomain.

Regards,

-- 
Julien Grall