diff --git a/Makefile b/Makefile
index 96f1c14..a85add2 100644
--- a/Makefile
+++ b/Makefile
@@ -79,7 +79,7 @@ $K/kernel: $(OBJS) $K/kernel.ld $U/initcode
 	$(OBJDUMP) -t $K/kernel | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > $K/kernel.sym
 
 $U/initcode: $U/initcode.S
-	$(CC) $(CFLAGS) -nostdinc -I. -Ikernel -c $U/initcode.S -o $U/initcode.o
+	$(CC) $(CFLAGS) -march=rv64g -nostdinc -I. -Ikernel -c $U/initcode.S -o $U/initcode.o
 	$(LD) $(LDFLAGS) -N -e start -Ttext 0 -o $U/initcode.out $U/initcode.o
 	$(OBJCOPY) -S -O binary $U/initcode.out $U/initcode
 	$(OBJDUMP) -S $U/initcode.o > $U/initcode.asm
diff --git a/README b/README
index 87a3833..06035bb 100644
--- a/README
+++ b/README
@@ -15,24 +15,26 @@ Clements.
 
 We are also grateful for the bug reports and patches contributed by
 Silas Boyd-Wickizer, Anton Burtsev, Dan Cross, Cody Cutler, Mike CAT,
-Tej Chajed, eyalz800, Nelson Elhage, Saar Ettinger, Alice Ferrazzi,
-Nathaniel Filardo, Peter Froehlich, Yakir Goaron,Shivam Handa, Bryan
-Henry, Jim Huang, Alexander Kapshuk, Anders Kaseorg, kehao95, Wolfgang
-Keller, Eddie Kohler, Austin Liew, Imbar Marinescu, Yandong Mao, Matan
-Shabtay, Hitoshi Mitake, Carmi Merimovich, Mark Morrissey, mtasm, Joel
-Nider, Greg Price, Ayan Shafqat, Eldar Sehayek, Yongming Shen, Cam
-Tenny, tyfkda, Rafael Ubal, Warren Toomey, Stephen Tu, Pablo Ventura,
-Xi Wang, Keiichi Watanabe, Nicolas Wolovick, wxdao, Grant Wu, Jindong
-Zhang, Icenowy Zheng, and Zou Chang Wei.
+Tej Chajed, Asami Doi, eyalz800, , Nelson Elhage, Saar Ettinger, Alice
+Ferrazzi, Nathaniel Filardo, Peter Froehlich, Yakir Goaron,Shivam
+Handa, Bryan Henry, jaichenhengjie, Jim Huang, Alexander Kapshuk,
+Anders Kaseorg, kehao95, Wolfgang Keller, Jonathan Kimmitt, Eddie
+Kohler, Austin Liew, Imbar Marinescu, Yandong Mao, Matan Shabtay,
+Hitoshi Mitake, Carmi Merimovich, Mark Morrissey, mtasm, Joel Nider,
+Greg Price, Ayan Shafqat, Eldar Sehayek, Yongming Shen, Fumiya
+Shigemitsu, Takahiro, Cam Tenny, tyfkda, Rafael Ubal, Warren Toomey,
+Stephen Tu, Pablo Ventura, Xi Wang, Keiichi Watanabe, Nicolas
+Wolovick, wxdao, Grant Wu, Jindong Zhang, Icenowy Zheng, and Zou Chang
+Wei.
 
 The code in the files that constitute xv6 is
-Copyright 2006-2019 Frans Kaashoek, Robert Morris, and Russ Cox.
+Copyright 2006-2020 Frans Kaashoek, Robert Morris, and Russ Cox.
 
 ERROR REPORTS
 
 Please send errors and suggestions to Frans Kaashoek and Robert Morris
 (kaashoek,rtm@mit.edu). The main purpose of xv6 is as a teaching
-operating system for MIT's 6.828, so we are more interested in
+operating system for MIT's 6.S081, so we are more interested in
 simplifications and clarifications than new features.
 
 BUILDING AND RUNNING XV6
diff --git a/doc/riscv-privileged-20190608-1.pdf b/doc/riscv-privileged-20190608-1.pdf
new file mode 100644
index 0000000..2303a01
Binary files /dev/null and b/doc/riscv-privileged-20190608-1.pdf differ
diff --git a/doc/riscv-privileged-v1.10.pdf b/doc/riscv-privileged-v1.10.pdf
deleted file mode 100644
index 6942fe7..0000000
Binary files a/doc/riscv-privileged-v1.10.pdf and /dev/null differ
diff --git a/doc/riscv-spec-20191213.pdf b/doc/riscv-spec-20191213.pdf
new file mode 100644
index 0000000..533c1cb
Binary files /dev/null and b/doc/riscv-spec-20191213.pdf differ
diff --git a/doc/riscv-spec-v2.2.pdf b/doc/riscv-spec-v2.2.pdf
deleted file mode 100644
index e4a4634..0000000
Binary files a/doc/riscv-spec-v2.2.pdf and /dev/null differ
diff --git a/kernel/entry.S b/kernel/entry.S
index ef5a56a..62fe1f2 100644
--- a/kernel/entry.S
+++ b/kernel/entry.S
@@ -1,7 +1,7 @@
 	# qemu -kernel starts at 0x1000. the instructions
         # there seem to be provided by qemu, as if it
         # were a ROM. the code at 0x1000 jumps to
-        # 0x8000000, the _start function here,
+        # 0x80000000, the _start function here,
         # in machine mode. each CPU starts here.
 .section .data
 .globl stack0
diff --git a/kernel/proc.c b/kernel/proc.c
index cf7f260..417e30a 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -183,13 +183,13 @@ proc_freepagetable(pagetable_t pagetable, uint64 sz)
 // a user program that calls exec("/init")
 // od -t xC initcode
 uchar initcode[] = {
-  0x17, 0x05, 0x00, 0x00, 0x13, 0x05, 0x05, 0x02,
-  0x97, 0x05, 0x00, 0x00, 0x93, 0x85, 0x05, 0x02,
-  0x9d, 0x48, 0x73, 0x00, 0x00, 0x00, 0x89, 0x48,
-  0x73, 0x00, 0x00, 0x00, 0xef, 0xf0, 0xbf, 0xff,
-  0x2f, 0x69, 0x6e, 0x69, 0x74, 0x00, 0x00, 0x01,
-  0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-  0x00, 0x00, 0x00
+  0x17, 0x05, 0x00, 0x00, 0x13, 0x05, 0x45, 0x02,
+  0x97, 0x05, 0x00, 0x00, 0x93, 0x85, 0x35, 0x02,
+  0x93, 0x08, 0x70, 0x00, 0x73, 0x00, 0x00, 0x00,
+  0x93, 0x08, 0x20, 0x00, 0x73, 0x00, 0x00, 0x00,
+  0xef, 0xf0, 0x9f, 0xff, 0x2f, 0x69, 0x6e, 0x69,
+  0x74, 0x00, 0x00, 0x24, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00
 };
 
 // Set up first user process.
diff --git a/kernel/ramdisk.c b/kernel/ramdisk.c
index 9901294..eb60ee7 100644
--- a/kernel/ramdisk.c
+++ b/kernel/ramdisk.c
@@ -1,5 +1,5 @@
 //
-// ramdisk that uses the disk image loaded by qemu -rdinit fs.img
+// ramdisk that uses the disk image loaded by qemu -initrd fs.img
 //
 
 #include "types.h"
diff --git a/kernel/virtio_disk.c b/kernel/virtio_disk.c
index 3cff024..06e0645 100644
--- a/kernel/virtio_disk.c
+++ b/kernel/virtio_disk.c
@@ -264,6 +264,7 @@ virtio_disk_intr()
 
     disk.used_idx = (disk.used_idx + 1) % NUM;
   }
+  *R(VIRTIO_MMIO_INTERRUPT_ACK) = *R(VIRTIO_MMIO_INTERRUPT_STATUS) & 0x3;
 
   release(&disk.vdisk_lock);
 }
diff --git a/kernel/vm.c b/kernel/vm.c
index d45210a..b48a022 100644
--- a/kernel/vm.c
+++ b/kernel/vm.c
@@ -65,9 +65,9 @@ kvminithart()
 // A 64-bit virtual address is split into five fields:
 //   39..63 -- must be zero.
 //   30..38 -- 9 bits of level-2 index.
-//   21..39 -- 9 bits of level-1 index.
+//   21..29 -- 9 bits of level-1 index.
 //   12..20 -- 9 bits of level-0 index.
-//    0..12 -- 12 bits of byte offset within the page.
+//    0..11 -- 12 bits of byte offset within the page.
 pte_t *
 walk(pagetable_t pagetable, uint64 va, int alloc)
 {