manatee/debugging: switching to manatee kernel.

We will have a 5.10-manatee branch for development until we can unfork.

BUG=b:216405078
TEST=read it.

Cq-Depend: chromium:3429139
Change-Id: I0287a1d67fb541f78910fa8f68732230fc0c011e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/docs/+/3438865
Reviewed-by: Mattias Nissler <mnissler@chromium.org>
Commit-Queue: Junichi Uekawa <uekawa@chromium.org>
Tested-by: Junichi Uekawa <uekawa@chromium.org>
diff --git a/manatee/boards.md b/manatee/boards.md
index aec44a4..a73d2fb 100644
--- a/manatee/boards.md
+++ b/manatee/boards.md
@@ -15,8 +15,9 @@
 
 ### Guest Kernel
 
-Unmodified chromeos kernel release 5.4 or 5.10. Paravirtualization support is
-enabled through USE flags added by project-manatee profile configuration.
+Unmodified chromeos kernel release 5.4 or modified 5.10-manatee
+kernel. Paravirtualization support is enabled through USE flags
+(such as `hypervisor_guest`) added by project-manatee profile configuration.
 
 ### Hardware Passthrough
 
@@ -87,8 +88,8 @@
 
 board           | status      | serial port | hypervisor kernel
 --------------- | ----------- | ----------- | -----------------
-brya-manatee    | build/boots | ttyS0       | 5.10
-volteer-manatee | build/boots | ttyS0       | 5.10
+brya-manatee    | build/boots | ttyS0       | 5.10-manatee
+volteer-manatee | build/boots | ttyS0       | 5.10-manatee
 
 ### Firmware issues
 
diff --git a/manatee/debugging.md b/manatee/debugging.md
index 64080d4..11d9cef 100644
--- a/manatee/debugging.md
+++ b/manatee/debugging.md
@@ -18,7 +18,7 @@
 -   Latest version: `sys-kernel/chromeos-kernel-5_4-manatee` or
     `sys-kernel/chromeos-kernel-5_10-manatee` on brya and volteer.
 -   Source directory: `src/third_party/kernel/v5.4-manatee/` or
-    `src/third_party/kernel/v5.10/` (shared with non-manatee kernel).
+    `src/third_party/kernel/v5.10-manatee/` (shared with non-manatee kernel).
 
 Build location is different than regular chromeos-kernel, placing all kernel
 binaries under `/build/${BOARD}/build/manatee/` directory. If `USE=manatee` is
@@ -30,6 +30,9 @@
 [`src/overlays/project-manatee/sys-kernel/chromeos-kernel-5_10-manatee/files`](https://source.chromium.org/chromiumos/chromiumos/codesearch/+/main:src/overlays/project-manatee/sys-kernel/chromeos-kernel-5_10-manatee/files/).
 TODO(b/201240038): remove.
 
+Kernel configuration is at
+`src/overlays/project-manatee/sys-kernel/chromeos-kernel-5_10-manatee/files/defconfig.x86_64`.
+
 ### InitramFS Image
 
 -   Package name: `chromeos-base/chromeos-initramfs`
@@ -49,6 +52,14 @@
 Instead of being on the kernel partition directly, the kernel image is contained
 in the initramfs as `/boot/vmlinuz` and deployed as part of manatee initramfs.
 
+Source is on `src/third_party/kernel/v5.4/` for 5.4 kernels.
+`src/third_party/kernel/v5.10-manatee/` for 5.10 kernels.
+
+Kernel configuration is using usual Chrome OS configuration mechanisms, with
+hypervisor USE flags enabled from project-manatee overlay.  See
+`src/third_party/chromiumos-overlay/eclass/cros-kernel2.eclass` for what flags
+are enabled with `hypervisor_guest`.
+
 ### SiblingOS kernel
 
 Virtual machines run as secondary guests are running at the same virtualization