Re: [PATCH V2 2/3] xen/arm: Add handling of extended regions for Dom0

[Oleksandr <olekstysh@xxxxxxxxx>]

Hi Stefano


[snip]


> > > > You will also need to cover "ranges" that will describe the BARs 
> > > > for the PCI
> > > > devices.
> > > Good point.
> > Yes, very good point!
> >
> >
> > > Could you please clarify how to recognize whether it is a PCI
> > > device as long as PCI support is not merged? Or just to find any 
> > > device nodes
> > > with non-empty "ranges" property
> > > and retrieve addresses?
> > Normally any bus can have a ranges property with the aperture and
> > possible address translations, including /amba (compatible =
> > "simple-bus"). However, in these cases dt_device_get_address already
> > takes care of it, see xen/common/device_tree.c:dt_device_get_address.
> >
> > The PCI bus is special for 2 reasons:
> > - the ranges property has a different format
> > - the bus is hot-pluggable
> >
> > So I think the only one that we need to treat specially is PCI.
> >
> > As far as I am aware PCI is the only bus (or maybe just the only bus
> > that we support?) where ranges means the aperture.
> Thank you for the clarification. I need to find device node with 
> non-empty ranges property
> (and make sure that device_type property is "pci"), after that I need 
> to read the context of ranges property and translate it.
OK, I experimented with that and managed to parse ranges property for 
PCI host bridge node.
I tested on my setup where the host device tree contains two PCI host 
bridge nodes with the following:
pcie@fe000000 {
...
            ranges = <0x1000000 0x0 0x0 0x0 0xfe100000 0x0 0x100000 
0x2000000 0x0 0xfe200000 0x0 0xfe200000 0x0 0x200000 0x2000000 0x0 
0x30000000 0x0 0x30000000 0x0 0x8000000 0x42000000 0x0 0x38000000 0x0 
0x38000000 0x0 0x8000000>;
...
};

pcie@ee800000 {
...
            ranges = <0x1000000 0x0 0x0 0x0 0xee900000 0x0 0x100000 
0x2000000 0x0 0xeea00000 0x0 0xeea00000 0x0 0x200000 0x2000000 0x0 
0xc0000000 0x0 0xc0000000 0x0 0x8000000 0x42000000 0x0 0xc8000000 0x0 
0xc8000000 0x0 0x8000000>;
...
};

So Xen retrieves the *CPU addresses* from the ranges:

(XEN) dev /soc/pcie@fe000000 range_size 7 nr_ranges 4
(XEN) 0: addr=fe100000, size=100000
(XEN) 1: addr=fe200000, size=200000
(XEN) 2: addr=30000000, size=8000000
(XEN) 3: addr=38000000, size=8000000
(XEN) dev /soc/pcie@ee800000 range_size 7 nr_ranges 4
(XEN) 0: addr=ee900000, size=100000
(XEN) 1: addr=eea00000, size=200000
(XEN) 2: addr=c0000000, size=8000000
(XEN) 3: addr=c8000000, size=8000000

The code below covers ranges property in the context of finding memory 
holes (to be squashed with current patch):
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index d37156a..7d20c10 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -834,6 +834,8 @@ static int __init find_memory_holes(struct meminfo 
*ext_regions)
     {
         unsigned int naddr;
         u64 addr, size;
+        const __be32 *ranges;
+        u32 len;

         naddr = dt_number_of_address(np);

@@ -857,6 +859,41 @@ static int __init find_memory_holes(struct meminfo 
*ext_regions)
                 goto out;
             }
         }
+
+        /*
+         * Also looking for non-empty ranges property which would 
likely mean
+         * that we deal with PCI host bridge device and the property here
+         * describes the BARs for the PCI devices.
+         */
+        ranges = dt_get_property(np, "ranges", &len);
+        if ( ranges && len )
+        {
+            unsigned int range_size, nr_ranges;
+            int na, ns, pna;
+
+            pna = dt_n_addr_cells(np);
+            na = dt_child_n_addr_cells(np);
+            ns = dt_child_n_size_cells(np);
+            range_size = pna + na + ns;
+            nr_ranges = len / sizeof(__be32) / range_size;
+
+            for ( i = 0; i < nr_ranges; i++, ranges += range_size )
+            {
+                /* Skip the child address and get the parent (CPU) 
address */
+                addr = dt_read_number(ranges + na, pna);
+                size = dt_read_number(ranges + na + pna, ns);
+
+                start = addr & PAGE_MASK;
+                end = PAGE_ALIGN(addr + size);
+                res = rangeset_remove_range(mem_holes, start, end - 1);
+                if ( res )
+                {
+                    printk(XENLOG_ERR "Failed to remove: 
%#"PRIx64"->%#"PRIx64"\n",
+                           start, end);
+                    goto out;
+                }
+            }
+        }
     }

     start = 0;



--
Regards,

Oleksandr Tyshchenko