Separate leaf page and directory pages USER flag

This is required for RISC-V. Privileged spec says:

> For non-leaf PTEs, the D, A, and U bits are reserved for future standard use.
> Until their use is defined by a standard extension, they must be cleared by software
> for forward compatibility.

QEMU fails address translation if it sees any of these flags set on non-leaf page entry.

src/arch/aarch64.rs

@@ -24,7 +24,7 @@ impl Arch for AArch64Arch {
     const ENTRY_FLAG_PRESENT: usize = 1 << 0;
     const ENTRY_FLAG_READONLY: usize = 1 << 7;
     const ENTRY_FLAG_READWRITE: usize = 0;
-    const ENTRY_FLAG_USER: usize = 1 << 6;
+    const ENTRY_FLAG_PAGE_USER: usize = 1 << 6;
     // This sets both userspace and privileged execute never
     //TODO: Separate the two?
     const ENTRY_FLAG_NO_EXEC: usize = 0b11 << 53;

src/arch/emulate.rs

@@ -20,7 +20,7 @@ impl Arch for EmulateArch {
     const ENTRY_FLAG_PRESENT: usize = X8664Arch::ENTRY_FLAG_PRESENT;
     const ENTRY_FLAG_READONLY: usize = X8664Arch::ENTRY_FLAG_READONLY;
     const ENTRY_FLAG_READWRITE: usize = X8664Arch::ENTRY_FLAG_READWRITE;
-    const ENTRY_FLAG_USER: usize = X8664Arch::ENTRY_FLAG_USER;
+    const ENTRY_FLAG_PAGE_USER: usize = X8664Arch::ENTRY_FLAG_PAGE_USER;
     const ENTRY_FLAG_NO_EXEC: usize = X8664Arch::ENTRY_FLAG_NO_EXEC;
     const ENTRY_FLAG_EXEC: usize = X8664Arch::ENTRY_FLAG_EXEC;
 

src/arch/mod.rs

@@ -36,7 +36,8 @@ pub trait Arch: Clone + Copy {
     const ENTRY_FLAG_PRESENT: usize;
     const ENTRY_FLAG_READONLY: usize;
     const ENTRY_FLAG_READWRITE: usize;
-    const ENTRY_FLAG_USER: usize;
+    const ENTRY_FLAG_PAGE_USER: usize; // Leaf table user page flag
+    const ENTRY_FLAG_TABLE_USER: usize = Self::ENTRY_FLAG_PAGE_USER; // Directory user page table flag
     const ENTRY_FLAG_NO_EXEC: usize;
     const ENTRY_FLAG_EXEC: usize;
     const ENTRY_FLAG_GLOBAL: usize;

src/arch/riscv64/sv39.rs

@@ -20,7 +20,8 @@ impl Arch for RiscV64Sv39Arch {
     const ENTRY_FLAG_PRESENT: usize = 1 << 0;
     const ENTRY_FLAG_READONLY: usize = 0;
     const ENTRY_FLAG_READWRITE: usize = 1 << 2;
-    const ENTRY_FLAG_USER: usize = 1 << 4;
+    const ENTRY_FLAG_PAGE_USER: usize = 1 << 4;
+    const ENTRY_FLAG_TABLE_USER: usize = 0;
     const ENTRY_FLAG_NO_EXEC: usize = 0;
     const ENTRY_FLAG_EXEC: usize = 1 << 3;
     const ENTRY_FLAG_GLOBAL: usize = 1 << 5;

src/arch/riscv64/sv48.rs

@@ -20,7 +20,8 @@ impl Arch for RiscV64Sv48Arch {
     const ENTRY_FLAG_PRESENT: usize = 1 << 0;
     const ENTRY_FLAG_READONLY: usize = 0;
     const ENTRY_FLAG_READWRITE: usize = 1 << 2;
-    const ENTRY_FLAG_USER: usize = 1 << 4;
+    const ENTRY_FLAG_PAGE_USER: usize = 1 << 4;
+    const ENTRY_FLAG_TABLE_USER: usize = 0;
     const ENTRY_FLAG_NO_EXEC: usize = 0;
     const ENTRY_FLAG_EXEC: usize = 1 << 3;
     const ENTRY_FLAG_GLOBAL: usize = 1 << 5;

src/arch/x86.rs

@@ -17,7 +17,7 @@ impl Arch for X86Arch {
     const ENTRY_FLAG_PRESENT: usize = 1 << 0;
     const ENTRY_FLAG_READONLY: usize = 0;
     const ENTRY_FLAG_READWRITE: usize = 1 << 1;
-    const ENTRY_FLAG_USER: usize = 1 << 2;
+    const ENTRY_FLAG_PAGE_USER: usize = 1 << 2;
     // Not used: const ENTRY_FLAG_HUGE: usize = 1 << 7;
     const ENTRY_FLAG_GLOBAL: usize = 1 << 8;
     const ENTRY_FLAG_NO_GLOBAL: usize = 0;

src/arch/x86_64.rs

@@ -16,7 +16,7 @@ impl Arch for X8664Arch {
     const ENTRY_FLAG_PRESENT: usize = 1 << 0;
     const ENTRY_FLAG_READONLY: usize = 0;
     const ENTRY_FLAG_READWRITE: usize = 1 << 1;
-    const ENTRY_FLAG_USER: usize = 1 << 2;
+    const ENTRY_FLAG_PAGE_USER: usize = 1 << 2;
     // Not used: const ENTRY_FLAG_HUGE: usize = 1 << 7;
     const ENTRY_FLAG_GLOBAL: usize = 1 << 8;
     const ENTRY_FLAG_NO_GLOBAL: usize = 0;

src/page/flags.rs

@@ -72,12 +72,12 @@ impl<A: Arch> PageFlags<A> {
     #[must_use]
     #[inline(always)]
     pub fn user(self, value: bool) -> Self {
-        self.custom_flag(A::ENTRY_FLAG_USER, value)
+        self.custom_flag(A::ENTRY_FLAG_PAGE_USER, value)
     }
 
     #[inline(always)]
     pub fn has_user(&self) -> bool {
-        self.has_flag(A::ENTRY_FLAG_USER)
+        self.has_flag(A::ENTRY_FLAG_PAGE_USER)
     }
 
     #[must_use]

src/page/mapper.rs

@@ -123,7 +123,7 @@ impl<A: Arch, F: FrameAllocator> PageMapper<A, F> {
                         let flags = A::ENTRY_FLAG_READWRITE
                             | A::ENTRY_FLAG_DEFAULT_TABLE
                             | if virt.kind() == TableKind::User {
-                                A::ENTRY_FLAG_USER
+                                A::ENTRY_FLAG_TABLE_USER
                             } else {
                                 0
                             };