Remove rv48 support, for it has no use and it's easy to add back when necessary

kernel/Cargo.toml

@@ -19,12 +19,10 @@ authors = [
 ]
 
 [features]
-default = ["sv39"]
-# Page table sv39 or sv48 (for riscv64)
-sv39 = []
-board_u540 = ["sv39", "link_user"]
-board_k210 = ["sv39", "link_user"]
-board_rocket_chip = ["sv39", "link_user"]
+default = []
+board_u540 = ["link_user"]
+board_k210 = ["link_user"]
+board_rocket_chip = ["link_user"]
 # (for aarch64 RaspberryPi3)
 nographic = []
 board_raspi3 = ["bcm2837", "link_user"]

kernel/src/arch/riscv32/paging.rs

@@ -13,10 +13,8 @@ use riscv::register::satp;
 
 #[cfg(target_arch = "riscv32")]
 type TopLevelPageTable<'a> = riscv::paging::Rv32PageTable<'a>;
-#[cfg(all(target_arch = "riscv64", feature = "sv39"))]
+#[cfg(target_arch = "riscv64")]
 type TopLevelPageTable<'a> = riscv::paging::Rv39PageTable<'a>;
-#[cfg(all(target_arch = "riscv64", not(feature = "sv39")))]
-type TopLevelPageTable<'a> = riscv::paging::Rv48PageTable<'a>;
 
 pub struct PageTableImpl {
     page_table: TopLevelPageTable<'static>,
@@ -191,20 +189,19 @@ impl PageTableExt for PageTableImpl {
             let frame = Frame::of_addr(PhysAddr::new((i << 22) - PHYSICAL_MEMORY_OFFSET));
             table[i].set(frame, flags);
         }
-        #[cfg(all(target_arch = "riscv64", feature = "sv39"))]
+        #[cfg(target_arch = "riscv64")]
         for i in 509..512 {
             let flags =
                 EF::VALID | EF::READABLE | EF::WRITABLE | EF::EXECUTABLE | EF::ACCESSED | EF::DIRTY;
             let frame = Frame::of_addr(PhysAddr::new((0xFFFFFF80_00000000 + (i << 30)) - PHYSICAL_MEMORY_OFFSET));
             table[i].set(frame, flags);
         }
-        // TODO: sv48
     }
 
     fn token(&self) -> usize {
         #[cfg(target_arch = "riscv32")]
         return self.root_frame.number() | (1 << 31);
-        #[cfg(all(target_arch = "riscv64", feature = "sv39"))]
+        #[cfg(target_arch = "riscv64")]
         return self.root_frame.number() | (8 << 60);
     }