linux: Reserve direct mmio in mmio allocator

Direct mmio range couldn't be assigned to any device, so this commit
exclude them from mmio allocator before build_vm().

BUG=None
TEST=tools/presubimt and boot manatee

Change-Id: I71414de1d44545e2c490ce75f5ced5545752858f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3605163
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>

src/linux/mod.rs

@@ -1310,6 +1310,22 @@ where
         irqs.push(direct_irq);
     }
 
+    // Reserve direct mmio range in advance.
+    #[cfg(feature = "direct")]
+    if let Some(mmio) = &cfg.direct_mmio {
+        for range in mmio.ranges.iter() {
+            sys_allocator
+                .reserve_mmio(range.base, range.len)
+                .with_context(|| {
+                    format!(
+                        "failed to reserved direct mmio: {:x}-{:x}",
+                        range.base,
+                        range.base + range.len - 1,
+                    )
+                })?;
+        }
+    };
+
     let mut iommu_attached_endpoints: BTreeMap<u32, Arc<Mutex<Box<dyn MemoryMapperTrait>>>> =
         BTreeMap::new();
     let mut iova_max_addr: Option<u64> = None;