[PATCH v2 3/6] x86/iommu: introduce a rangeset to perform hwdom IOMMU setup

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

This change just introduces the boilerplate code in order to use a rangeset
when setting up the hardware domain IOMMU mappings.  The rangeset is never
populated in this patch, so it's a non-functional change as far as the mappings
the domain gets established.

Note there's a change for HVM domains (ie: PVH dom0) that will get switched to
create the p2m mappings using map_mmio_regions() instead of
p2m_add_identity_entry(), so that ranges can be mapped with a single function
call if possible.  Note that the interface of map_mmio_regions() doesn't allow
creating read-only mappings, but so far there are no such mappings created for
PVH dom0 in arch_iommu_hwdom_init().

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes since v1:
 - Split from bigger patch.
---
 xen/drivers/passthrough/x86/iommu.c | 89 +++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

diff --git a/xen/drivers/passthrough/x86/iommu.c 
b/xen/drivers/passthrough/x86/iommu.c
index 857dccb6a465..531a428f6496 100644
--- a/xen/drivers/passthrough/x86/iommu.c
+++ b/xen/drivers/passthrough/x86/iommu.c
@@ -370,10 +370,77 @@ static unsigned int __hwdom_init hwdom_iommu_map(const 
struct domain *d,
     return perms;
 }
 
+struct map_data {
+    struct domain *d;
+    unsigned int flush_flags;
+    bool ro;
+};
+
+static int __hwdom_init cf_check identity_map(unsigned long s, unsigned long e,
+                                              void *data)
+{
+    struct map_data *info = data;
+    struct domain *d = info->d;
+    long rc;
+
+    if ( iommu_verbose )
+        printk(XENLOG_INFO " [%010lx, %010lx] R%c\n",
+               s, e, info->ro ? 'O' : 'W');
+
+    if ( paging_mode_translate(d) )
+    {
+        if ( info->ro )
+        {
+            ASSERT_UNREACHABLE();
+            return 0;
+        }
+        while ( (rc = map_mmio_regions(d, _gfn(s), e - s + 1, _mfn(s))) > 0 )
+        {
+            s += rc;
+            process_pending_softirqs();
+        }
+    }
+    else
+    {
+        const unsigned int perms = IOMMUF_readable | IOMMUF_preempt |
+                                   (info->ro ? 0 : IOMMUF_writable);
+
+        if ( info->ro && !iomem_access_permitted(d, s, e) )
+        {
+            /*
+             * Should be more fine grained in order to not map the forbidden
+             * frame instead of rejecting the region as a whole, but it's only
+             * for read-only MMIO regions, which are very limited.
+             */
+            printk(XENLOG_DEBUG
+                   "IOMMU read-only mapping of region [%lx, %lx] forbidden\n",
+                   s, e);
+            return 0;
+        }
+        while ( (rc = iommu_map(d, _dfn(s), _mfn(s), e - s + 1,
+                                perms, &info->flush_flags)) > 0 )
+        {
+            s += rc;
+            process_pending_softirqs();
+        }
+    }
+    ASSERT(rc <= 0);
+    if ( rc )
+        printk(XENLOG_WARNING
+               "IOMMU identity mapping of [%lx, %lx] failed: %ld\n",
+               s, e, rc);
+
+    /* Ignore errors and attempt to map the remaining regions. */
+    return 0;
+}
+
 void __hwdom_init arch_iommu_hwdom_init(struct domain *d)
 {
     unsigned long i, top, max_pfn, start, count;
     unsigned int flush_flags = 0, start_perms = 0;
+    struct rangeset *map;
+    struct map_data map_data = { .d = d };
+    int rc;
 
     BUG_ON(!is_hardware_domain(d));
 
@@ -397,6 +464,10 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain *d)
     if ( iommu_hwdom_passthrough )
         return;
 
+    map = rangeset_new(NULL, NULL, 0);
+    if ( !map )
+        panic("IOMMU init: unable to allocate rangeset\n");
+
     max_pfn = (GB(4) >> PAGE_SHIFT) - 1;
     top = max(max_pdx, pfn_to_pdx(max_pfn) + 1);
 
@@ -451,6 +522,24 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain *d)
             goto commit;
     }
 
+    if ( iommu_verbose )
+        printk(XENLOG_INFO "d%u: identity mappings for IOMMU:\n",
+               d->domain_id);
+
+    rc = rangeset_report_ranges(map, 0, ~0UL, identity_map, &map_data);
+    if ( rc )
+        panic("IOMMU unable to create mappings: %d\n", rc);
+    if ( is_pv_domain(d) )
+    {
+        map_data.ro = true;
+        rc = rangeset_report_ranges(mmio_ro_ranges, 0, ~0UL, identity_map,
+                                    &map_data);
+        if ( rc )
+            panic("IOMMU unable to create read-only mappings: %d\n", rc);
+    }
+
+    rangeset_destroy(map);
+
     /* Use if to avoid compiler warning */
     if ( iommu_iotlb_flush_all(d, flush_flags) )
         return;
-- 
2.43.0