Re: [Xen-devel] [PATCH v2] iommu: setup inclusive mappings before enabling iommu

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Mon, Sep 17, 2018 at 06:49:24AM -0600, Jan Beulich wrote:
> >>> On 14.09.18 at 15:58, <roger.pau@xxxxxxxxxx> wrote:
> > Or else it can lead to freezes when enabling the iommu on certain
> > Intel hardware:
> > 
> > [...]
> > (XEN) ELF: addresses:
> > (XEN)     virt_base        = 0xffffffff80000000
> > (XEN)     elf_paddr_offset = 0x0
> > (XEN)     virt_offset      = 0xffffffff80000000
> > (XEN)     virt_kstart      = 0xffffffff81000000
> > (XEN)     virt_kend        = 0xffffffff82953000
> > (XEN)     virt_entry       = 0xffffffff8274e180
> > (XEN)     p2m_base         = 0x8000000000
> > (XEN)  Xen  kernel: 64-bit, lsb, compat32
> > (XEN)  Dom0 kernel: 64-bit, PAE, lsb, paddr 0x1000000 -> 0x295300
> > <freeze>
> > 
> > This restores the behavior before commit 66a9274cc3435 that changed
> > the order and enabled the iommu without having the inclusive mappings
> > setup.
> > 
> > Note that on AMD hardware the order is also changed to add inclusive
> > mappings before adding any devices.
> > 
> > Reported-by: Dario Faggioli <dfaggioli@xxxxxxxx>
> > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> 
> With the exception of the ARM aspect (because it's not
> clear to me why the code removed from iommu_hwdom_init()
> doesn't need to re-appear in ARM-specific code as well)
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

I guess you mean the following chunk:

-    if ( iommu_hwdom_inclusive && !is_pv_domain(d) )
-    {
-        printk(XENLOG_WARNING
-               "IOMMU inclusive mappings are only supported on PV Dom0\n");
-        iommu_hwdom_inclusive = 0;
-    }

I haven't added it for ARM because iommu_hwdom_inclusive is always set
to 0 in the ARM case, so the condition would never match.

Thanks, Roger.

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