Add GRUB bootloader patches for talosctl upgrade on RPi5/CM5

Force GRUB instead of sd-boot on arm64 and pass --no-nvram to
  grub-install, working around the SetVariableRT firmware limitation
  that prevents in-place upgrades on RPi5/CM5 hardware.

  Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -46,37 +46,27 @@ zstd -d metal-arm64.raw.zst -o metal-arm64.raw
 
 ### Upgrade an existing node
 
-> **Warning:** In-place upgrades via `talosctl upgrade` may fail on RPi5/CM5 hardware with a `SetVariableRT` EFI firmware error. See [Known issues](#known-issues) below. For now, the recommended upgrade path is to re-flash the disk image.
+```bash
+talosctl upgrade --image docker.io/svrnty/talos-rpi5:v1.12.3-k6.12.47-2
+```
+
+> **Note:** In-place upgrades use GRUB with `--no-nvram` to work around the RPi5/CM5 `SetVariableRT` firmware limitation. This patch is included but not yet tested in production — re-flashing the disk image is the proven fallback.
 
 ```bash
-# Re-flash method (reliable)
+# Fallback: re-flash method
 zstd -d metal-arm64.raw.zst -o metal-arm64.raw
 # Flash to eMMC/SD via your preferred tool
-
-# In-place method (experimental — may fail, see known issues)
-talosctl upgrade --image docker.io/svrnty/talos-rpi5:v1.12.3-k6.12.47-2
 ```
 
 ### What's included
 
 - RPi downstream kernel with CM5/RP1 support (4K page size, aligned with upstream Talos)
+- GRUB bootloader with `--no-nvram` for reliable `talosctl upgrade` on RPi5/CM5
 - Overclock: 2.6GHz (`arm_freq=2600`, `over_voltage_delta=50000`, `arm_boost=1`)
 - Extensions: `iscsi-tools`, `util-linux-tools`
 
 ## Known issues
 
-### In-place upgrade fails (SetVariableRT)
-
-`talosctl upgrade` may fail during the bootloader installation step with:
-
-```
-Firmware does not support SetVariableRT. Can not remount with rw
-```
-
-The RPi5/CM5 EFI firmware does not support runtime EFI variable writes, which the Talos bootloader update requires. **Re-flashing the disk image is the reliable upgrade path for now.** We are investigating GRUB-based boot as a fix (see [Roadmap](#roadmap)).
-
-*Upstream: <a href="https://github.com/talos-rpi5/talos-builder/issues/21" target="_blank">talos-builder#21</a>*
-
 ### No serial console output after boot
 
 Serial output goes silent after the EFI stub decompresses the kernel and exits boot services. This affects headless debugging on CM5 boards where serial is the primary console.
@@ -91,12 +81,14 @@ Talos ignores the `machine.install.disk` config field on SBC platforms. You **mu
 
 ## Roadmap
 
-This project targets production-ready Talos clusters on RPi5/CM5 hardware. Key milestones:
+This project targets production-ready Talos clusters on RPi5/CM5 hardware.
 
-- [x] **Switch to 4K page size** — Aligned with upstream Talos kernel config. Reduces memory overhead and improves workload compatibility (Longhorn, jemalloc, F2FS, etc.).
-- [ ] **Reliable in-place upgrades** — Investigate GRUB-based boot or alternative bootloader strategies to work around the `SetVariableRT` firmware limitation, enabling `talosctl upgrade` on RPi5/CM5.
-- [ ] **Serial console fix** — Debug U-Boot/kernel handoff to restore serial output after EFI stub exit.
-- [ ] **NVMe boot support** — Produce images that target NVMe directly, or document a supported NVMe boot flow.
+| Status | Milestone | Description |
+|--------|-----------|-------------|
+| Untested | **4K page size** | Aligned with upstream Talos kernel config. Reduces memory overhead and improves workload compatibility (Longhorn, jemalloc, F2FS, etc.). |
+| Untested | **Reliable in-place upgrades** | Force GRUB bootloader with `--no-nvram` on arm64 to work around the `SetVariableRT` firmware limitation (<a href="https://github.com/talos-rpi5/talos-builder/issues/21" target="_blank">talos-builder#21</a>). |
+| Pending | **Serial console fix** | Debug U-Boot/kernel handoff to restore serial output after EFI stub exit. |
+| Pending | **NVMe boot support** | Produce images that target NVMe directly, or document a supported NVMe boot flow. |
 
 ## Building
 

TECHNICAL.md

@@ -79,6 +79,8 @@ patches/
   siderolabs/
     pkgs/0001-*.patch      # RPi kernel patch
     talos/0001-*.patch     # Module list patch
+    talos/0002-*.patch     # Skip NVRAM writes for GRUB on arm64
+    talos/0003-*.patch     # Force GRUB bootloader on arm64
   talos-rpi5/
     sbc-raspberrypi5/      # Overlay patches (Go toolchain bump)
 cosign.pub                 # Public key for verifying image attestations

patches/siderolabs/talos/0002-Skip-NVRAM-writes-for-GRUB-on-arm64.patch

@@ -0,0 +1,33 @@
+From 2db8797af370535aba7c5694cd291bba8e6c5a67 Mon Sep 17 00:00:00 2001
+From: Mathias Beaulieu-Duncan <mathias@svrnty.io>
+Date: Fri, 13 Feb 2026 19:08:41 -0500
+Subject: [PATCH 2/3] Skip NVRAM writes for GRUB on arm64
+
+On arm64 platforms like RPi5/CM5, the UEFI firmware (U-Boot) does not
+support EFI runtime SetVariable, causing grub-install to fail when
+efibootmgr tries to create NVRAM boot entries. Since arm64-efi systems
+boot by convention (finding BOOTAA64.efi on the ESP), NVRAM boot
+entries are unnecessary.
+
+Pass --no-nvram to grub-install on arm64 to allow in-place upgrades
+via talosctl upgrade to succeed.
+---
+ .../machined/pkg/runtime/v1alpha1/bootloader/grub/install.go    | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/internal/app/machined/pkg/runtime/v1alpha1/bootloader/grub/install.go b/internal/app/machined/pkg/runtime/v1alpha1/bootloader/grub/install.go
+index 6f5c9f8..766374b 100644
+--- a/internal/app/machined/pkg/runtime/v1alpha1/bootloader/grub/install.go
++++ b/internal/app/machined/pkg/runtime/v1alpha1/bootloader/grub/install.go
+@@ -196,7 +196,7 @@ func (c *Config) install(opts options.InstallOptions) (*options.InstallResult, e
+ 			args = append(args, "--efi-directory="+filepath.Join(opts.MountPrefix, constants.EFIMountPoint))
+ 		}
+ 
+-		if opts.ImageMode {
++		if opts.ImageMode || opts.Arch == arm64 {
+ 			args = append(args, "--no-nvram")
+ 		}
+ 
+-- 
+2.50.1 (Apple Git-155)
+

patches/siderolabs/talos/0003-Force-GRUB-bootloader-on-arm64.patch

@@ -0,0 +1,47 @@
+From 1393b3f013e758f6bb52d14006d3a7e7db348930 Mon Sep 17 00:00:00 2001
+From: Mathias Beaulieu-Duncan <mathias@svrnty.io>
+Date: Fri, 13 Feb 2026 19:08:58 -0500
+Subject: [PATCH 3/3] Force GRUB bootloader on arm64
+
+On arm64 platforms like RPi5/CM5, the UEFI firmware (U-Boot) exposes
+/sys/firmware/efi but does not support EFI runtime SetVariable. This
+causes NewAuto() to select sd-boot, which then fails when trying to
+write EFI variables during installation/upgrade.
+
+Force GRUB on arm64 since it uses config files instead of EFI
+variables for boot configuration. Combined with the --no-nvram patch,
+this enables reliable in-place upgrades via talosctl upgrade on
+RPi5/CM5 hardware.
+
+Ref: https://github.com/siderolabs/talos/issues/10859
+Ref: https://github.com/talos-rpi5/talos-builder/issues/21
+---
+ .../machined/pkg/runtime/v1alpha1/bootloader/bootloader.go   | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/internal/app/machined/pkg/runtime/v1alpha1/bootloader/bootloader.go b/internal/app/machined/pkg/runtime/v1alpha1/bootloader/bootloader.go
+index f084e09..5c388c1 100644
+--- a/internal/app/machined/pkg/runtime/v1alpha1/bootloader/bootloader.go
++++ b/internal/app/machined/pkg/runtime/v1alpha1/bootloader/bootloader.go
+@@ -8,6 +8,7 @@ package bootloader
+ import (
+ 	"fmt"
+ 	"os"
++	goruntime "runtime"
+ 
+ 	"github.com/siderolabs/go-blockdevice/v2/block"
+ 	"github.com/siderolabs/go-blockdevice/v2/partitioning/gpt"
+@@ -73,6 +74,10 @@ func Probe(disk string, options options.ProbeOptions) (Bootloader, error) {
+ 
+ // NewAuto returns a new bootloader based on auto-detection.
+ func NewAuto() Bootloader {
++	if goruntime.GOARCH == "arm64" {
++		return grub.NewConfig()
++	}
++
+ 	if sdboot.IsUEFIBoot() {
+ 		return sdboot.New()
+ 	}
+-- 
+2.50.1 (Apple Git-155)
+