xen/arm: Add handling of extended regions for Dom0

The extended region (safe range) is a region of guest physical
address space which is unused and could be safely used to create
grant/foreign mappings instead of wasting real RAM pages from
the domain memory for establishing these mappings.

The extended regions are chosen at the domain creation time and
advertised to it via "reg" property under hypervisor node in
the guest device-tree. As region 0 is reserved for grant table
space (always present), the indexes for extended regions are 1...N.
If extended regions could not be allocated for some reason,
Xen doesn't fail and behaves as usual, so only inserts region 0.

Please note the following limitations:
- The extended region feature is only supported for 64-bit domain
  currently.
- The ACPI case is not covered.

***

As Dom0 is direct mapped domain on Arm (e.g. MFN == GFN)
the algorithm to choose extended regions for it is different
in comparison with the algorithm for non-direct mapped DomU.
What is more, that extended regions should be chosen differently
whether IOMMU is enabled or not.

Provide RAM not assigned to Dom0 if IOMMU is disabled or memory
holes found in host device-tree if otherwise. Make sure that
extended regions are 2MB-aligned and located within maximum possible
addressable physical memory range. The minimum size of extended
region is 64MB. The maximum number of extended regions is 128,
which is an artificial limit to minimize code changes (we reuse
struct meminfo to describe extended regions, so there are an array
field for 128 elements).

It worth mentioning that unallocated memory solution (when the IOMMU
is disabled) will work safely until Dom0 is able to allocate memory
outside of the original range.

Also introduce command line option to be able to globally enable or
disable support for extended regions for Dom0 (enabled by default).

Suggested-by: Julien Grall <jgrall@amazon.com>
Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc
index 177e656f12b731649ef4de0dcc1246f97d2d30e0..5cae4adc584a2aa7702e7539d55b5187af3e1189 100644 (file)
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -1081,6 +1081,17 @@ hardware domain is architecture dependent.
 Note that specifying zero as domU value means zero, while for dom0 it means
 to use the default.
 
+### ext_regions (Arm)
+> `= <boolean>`
+
+> Default : `true`
+
+Flag to enable or disable support for extended regions for Dom0.
+
+Extended regions are ranges of unused address space exposed to Dom0 as
+"safe to use" for special memory mappings. Disable if your board device
+tree is incomplete.
+
 ### flask
 > `= permissive | enforcing | late | disabled`
 

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index d233d634c11271b33e72a19f71c48e834f35e986..c5afbe2e0521b39f337309aefe996297773c67ee 100644 (file)
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -34,6 +34,10 @@
 static unsigned int __initdata opt_dom0_max_vcpus;
 integer_param("dom0_max_vcpus", opt_dom0_max_vcpus);
 
+/* If true, the extended regions support is enabled for dom0 */
+static bool __initdata opt_ext_regions = true;
+boolean_param("ext_regions", opt_ext_regions);
+
 static u64 __initdata dom0_mem;
 static bool __initdata dom0_mem_set;
 
@@ -886,6 +890,232 @@ static int __init make_memory_node(const struct domain *d,
     return res;
 }
 
+static int __init add_ext_regions(unsigned long s, unsigned long e, void *data)
+{
+    struct meminfo *ext_regions = data;
+    paddr_t start, size;
+
+    if ( ext_regions->nr_banks >= ARRAY_SIZE(ext_regions->bank) )
+        return 0;
+
+    /* Both start and size of the extended region should be 2MB aligned */
+    start = (s + SZ_2M - 1) & ~(SZ_2M - 1);
+    if ( start > e )
+        return 0;
+
+    /*
+     * e is actually "end-1" because it is called by rangeset functions
+     * which are inclusive of the last address.
+     */
+    e += 1;
+    size = (e - start) & ~(SZ_2M - 1);
+    if ( size < MB(64) )
+        return 0;
+
+    ext_regions->bank[ext_regions->nr_banks].start = start;
+    ext_regions->bank[ext_regions->nr_banks].size = size;
+    ext_regions->nr_banks++;
+
+    return 0;
+}
+
+static int __init find_unallocated_memory(const struct kernel_info *kinfo,
+                                          struct meminfo *ext_regions)
+{
+    const struct meminfo *assign_mem = &kinfo->mem;
+    struct rangeset *unalloc_mem;
+    paddr_t start, end;
+    unsigned int i;
+    int res;
+
+    dt_dprintk("Find unallocated memory for extended regions\n");
+
+    unalloc_mem = rangeset_new(NULL, NULL, 0);
+    if ( !unalloc_mem )
+        return -ENOMEM;
+
+    /* Start with all available RAM */
+    for ( i = 0; i < bootinfo.mem.nr_banks; i++ )
+    {
+        start = bootinfo.mem.bank[i].start;
+        end = bootinfo.mem.bank[i].start + bootinfo.mem.bank[i].size;
+        res = rangeset_add_range(unalloc_mem, start, end - 1);
+        if ( res )
+        {
+            printk(XENLOG_ERR "Failed to add: %#"PRIx64"->%#"PRIx64"\n",
+                   start, end);
+            goto out;
+        }
+    }
+
+    /* Remove RAM assigned to Dom0 */
+    for ( i = 0; i < assign_mem->nr_banks; i++ )
+    {
+        start = assign_mem->bank[i].start;
+        end = assign_mem->bank[i].start + assign_mem->bank[i].size;
+        res = rangeset_remove_range(unalloc_mem, start, end - 1);
+        if ( res )
+        {
+            printk(XENLOG_ERR "Failed to remove: %#"PRIx64"->%#"PRIx64"\n",
+                   start, end);
+            goto out;
+        }
+    }
+
+    /* Remove reserved-memory regions */
+    for ( i = 0; i < bootinfo.reserved_mem.nr_banks; i++ )
+    {
+        start = bootinfo.reserved_mem.bank[i].start;
+        end = bootinfo.reserved_mem.bank[i].start +
+            bootinfo.reserved_mem.bank[i].size;
+        res = rangeset_remove_range(unalloc_mem, start, end - 1);
+        if ( res )
+        {
+            printk(XENLOG_ERR "Failed to remove: %#"PRIx64"->%#"PRIx64"\n",
+                   start, end);
+            goto out;
+        }
+    }
+
+    /* Remove grant table region */
+    start = kinfo->gnttab_start;
+    end = kinfo->gnttab_start + kinfo->gnttab_size;
+    res = rangeset_remove_range(unalloc_mem, start, end - 1);
+    if ( res )
+    {
+        printk(XENLOG_ERR "Failed to remove: %#"PRIx64"->%#"PRIx64"\n",
+               start, end);
+        goto out;
+    }
+
+    start = 0;
+    end = (1ULL << p2m_ipa_bits) - 1;
+    res = rangeset_report_ranges(unalloc_mem, start, end,
+                                 add_ext_regions, ext_regions);
+    if ( res )
+        ext_regions->nr_banks = 0;
+    else if ( !ext_regions->nr_banks )
+        res = -ENOENT;
+
+out:
+    rangeset_destroy(unalloc_mem);
+
+    return res;
+}
+
+static int __init find_memory_holes(const struct kernel_info *kinfo,
+                                    struct meminfo *ext_regions)
+{
+    struct dt_device_node *np;
+    struct rangeset *mem_holes;
+    paddr_t start, end;
+    unsigned int i;
+    int res;
+
+    dt_dprintk("Find memory holes for extended regions\n");
+
+    mem_holes = rangeset_new(NULL, NULL, 0);
+    if ( !mem_holes )
+        return -ENOMEM;
+
+    /* Start with maximum possible addressable physical memory range */
+    start = 0;
+    end = (1ULL << p2m_ipa_bits) - 1;
+    res = rangeset_add_range(mem_holes, start, end);
+    if ( res )
+    {
+        printk(XENLOG_ERR "Failed to add: %#"PRIx64"->%#"PRIx64"\n",
+               start, end);
+        goto out;
+    }
+
+    /*
+     * Remove regions described by "reg" and "ranges" properties where
+     * the memory is addressable (MMIO, RAM, PCI BAR, etc).
+     */
+    dt_for_each_device_node( dt_host, np )
+    {
+        unsigned int naddr;
+        u64 addr, size;
+
+        naddr = dt_number_of_address(np);
+
+        for ( i = 0; i < naddr; i++ )
+        {
+            res = dt_device_get_address(np, i, &addr, &size);
+            if ( res )
+            {
+                printk(XENLOG_ERR "Unable to retrieve address %u for %s\n",
+                       i, dt_node_full_name(np));
+                goto out;
+            }
+
+            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;
+            }
+        }
+
+        if ( dt_device_type_is_equal(np, "pci" ) )
+        {
+            unsigned int range_size, nr_ranges;
+            int na, ns, pna;
+            const __be32 *ranges;
+            u32 len;
+
+            /*
+             * Looking for non-empty ranges property which in this context
+             * describes the PCI host bridge aperture.
+             */
+            ranges = dt_get_property(np, "ranges", &len);
+            if ( !ranges || !len )
+                continue;
+
+            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;
+    end = (1ULL << p2m_ipa_bits) - 1;
+    res = rangeset_report_ranges(mem_holes, start, end,
+                                 add_ext_regions,  ext_regions);
+    if ( res )
+        ext_regions->nr_banks = 0;
+    else if ( !ext_regions->nr_banks )
+        res = -ENOENT;
+
+out:
+    rangeset_destroy(mem_holes);
+
+    return res;
+}
+
 static int __init make_hypervisor_node(struct domain *d,
                                        const struct kernel_info *kinfo,
                                        int addrcells, int sizecells)
@@ -893,11 +1123,12 @@ static int __init make_hypervisor_node(struct domain *d,
     const char compat[] =
         "xen,xen-"__stringify(XEN_VERSION)"."__stringify(XEN_SUBVERSION)"\0"
         "xen,xen";
-    __be32 reg[4];
+    __be32 *reg, *cells;
     gic_interrupt_t intr;
-    __be32 *cells;
     int res;
     void *fdt = kinfo->fdt;
+    struct meminfo *ext_regions = NULL;
+    unsigned int i, nr_ext_regions;
 
     dt_dprintk("Create hypervisor node\n");
 
@@ -919,12 +1150,61 @@ static int __init make_hypervisor_node(struct domain *d,
     if ( res )
         return res;
 
+    if ( !opt_ext_regions )
+    {
+        printk(XENLOG_DEBUG "The extended regions support is disabled\n");
+        nr_ext_regions = 0;
+    }
+    else if ( is_32bit_domain(d) )
+    {
+        printk(XENLOG_DEBUG "The extended regions are only supported for 64-bit guest currently\n");
+        nr_ext_regions = 0;
+    }
+    else
+    {
+        ext_regions = xzalloc(struct meminfo);
+        if ( !ext_regions )
+            return -ENOMEM;
+
+        if ( !is_iommu_enabled(d) )
+            res = find_unallocated_memory(kinfo, ext_regions);
+        else
+            res = find_memory_holes(kinfo, ext_regions);
+
+        if ( res )
+            printk(XENLOG_WARNING "Failed to allocate extended regions\n");
+        nr_ext_regions = ext_regions->nr_banks;
+    }
+
+    reg = xzalloc_array(__be32, (nr_ext_regions + 1) * (addrcells + sizecells));
+    if ( !reg )
+    {
+        xfree(ext_regions);
+        return -ENOMEM;
+    }
+
     /* reg 0 is grant table space */
     cells = &reg[0];
     dt_child_set_range(&cells, addrcells, sizecells,
                        kinfo->gnttab_start, kinfo->gnttab_size);
+    /* reg 1...N are extended regions */
+    for ( i = 0; i < nr_ext_regions; i++ )
+    {
+        u64 start = ext_regions->bank[i].start;
+        u64 size = ext_regions->bank[i].size;
+
+        dt_dprintk("Extended region %d: %#"PRIx64"->%#"PRIx64"\n",
+                   i, start, start + size);
+
+        dt_child_set_range(&cells, addrcells, sizecells, start, size);
+    }
+
     res = fdt_property(fdt, "reg", reg,
-                       dt_cells_to_size(addrcells + sizecells));
+                       dt_cells_to_size(addrcells + sizecells) *
+                       (nr_ext_regions + 1));
+    xfree(ext_regions);
+    xfree(reg);
+
     if ( res )
         return res;