Merge branch 'main' into zc-working

microsoft · Feb 1, 2025 · 5160924 · 5160924
2 parents a243d2b + 495daf6
commit 5160924
Show file tree

Hide file tree

Showing 3 changed files with 30 additions and 5 deletions.
diff --git a/openhcl/host_fdt_parser/src/lib.rs b/openhcl/host_fdt_parser/src/lib.rs
@@ -236,6 +236,8 @@ pub struct ParsedDeviceTree<
     pub device_dma_page_count: Option<u64>,
     /// Indicates that Host does support NVMe keep-alive.
     pub nvme_keepalive: bool,
+    /// The physical address of the VTL0 alias mapping, if one is configured.
+    pub vtl0_alias_map: Option<u64>,
 }
 
 /// The memory allocation mode provided by the host. This determines how OpenHCL
@@ -316,6 +318,7 @@ impl<
             entropy: None,
             device_dma_page_count: None,
             nvme_keepalive: false,
+            vtl0_alias_map: None,
         }
     }
 
@@ -483,6 +486,13 @@ impl<
                         }
                     }
 
+                    storage.vtl0_alias_map = child
+                        .find_property("vtl0-alias-map")
+                        .map_err(ErrorKind::Prop)?
+                        .map(|p| p.read_u64(0))
+                        .transpose()
+                        .map_err(ErrorKind::Prop)?;
+
                     for openhcl_child in child.children() {
                         let openhcl_child = openhcl_child.map_err(|error| ErrorKind::Node {
                             parent_name: root.name,
@@ -727,6 +737,7 @@ impl<
             entropy: _,
             device_dma_page_count: _,
             nvme_keepalive: _,
+            vtl0_alias_map: _,
         } = storage;
 
         *device_tree_size = parser.total_size;

diff --git a/openhcl/openhcl_boot/src/host_params/dt.rs b/openhcl/openhcl_boot/src/host_params/dt.rs
@@ -510,6 +510,11 @@ impl PartitionInfo {
             storage.vtl2_pool_memory = pool;
         }
 
+        // If we can trust the host, use the provided alias map
+        if can_trust_host {
+            storage.vtl0_alias_map = parsed.vtl0_alias_map;
+        }
+
         // Set remaining struct fields before returning.
         let Self {
             vtl2_ram: _,

diff --git a/openhcl/openhcl_boot/src/main.rs b/openhcl/openhcl_boot/src/main.rs
@@ -611,14 +611,23 @@ fn shim_main(shim_params_raw_offset: isize) -> ! {
         )
         .vtl0_alias_map_available()
     {
-        // Disable the alias map on ARM because physical address size is not
-        // reliably reported. Since the position of the alias map bit is inferred
-        // from address size, the alias map is broken when the PA size is wrong.
-        // TODO: is this still true?
-        if !cfg!(target_arch = "aarch64") {
+        // If the vtl0 alias map was not provided in the devicetree, attempt to
+        // derive it from the architectural physical address bits.
+        //
+        // The value in the ID_AA64MMFR0_EL1 register used to determine the
+        // physical address bits can only represent multiples of 4. As a result,
+        // the Surface Pro X (and systems with similar CPUs) cannot properly
+        // report their address width of 39 bits. This causes the calculated
+        // alias map to be incorrect, which results in panics when trying to
+        // read memory and getting invalid data.
+        if partition_info.vtl0_alias_map.is_none() {
             partition_info.vtl0_alias_map =
                 Some(1 << (arch::physical_address_bits(p.isolation_type) - 1));
         }
+    } else {
+        // Ignore any devicetree-provided alias map if the conditions above
+        // aren't met.
+        partition_info.vtl0_alias_map = None;
     }
 
     if can_trust_host {