[SRU] Crash on RISC-V in virtual machine using KVM

[Heinrich Schuchardt]

[ Impact ]

On RISC-V hardware offering the hypervisor extension GRUB crashes in virtual machines running under KVM due to missing accessibility of the counter register.

For measuring time the RISC-V ISA provides the time register.

Please, apply the following patch:

[PATCH 1/1] riscv: use time register in grub_efi_get_time_ms()
https://lists.gnu.org/archive/html/grub-devel/2024-08/msg00008.html

[ Test Plan ]

To reproduce the error run Ubuntu on QEMU according to https://wiki.ubuntu.com/RISC-V/QEMU on an HiFive P550 Premier. Add '-accel kvm' to the command line to use KVM. GRUB crashes.

Run Ubuntu on QEMU according to https://wiki.ubuntu.com/RISC-V/QEMU.

In GRUB press the <C>-key to enter the console.

Execute 'sleep 10' and check that the console prompt is written after approximately 10 seconds.

Restart the VM with the 'reset' command.

Check that the countdown in the Ubuntu menu runs at wall time speed.

Check that the login prompt is reached.

Correct timing under KVM depends on LP #2076927.

[ Where problems could occur ]

The patch only concerns RISC-V. It changes how GRUB measures elapsed time.

Incorrect measuring of time could lead to the menu countdown or the sleep command not working.

[ Other Info ]

n/a

[Heinrich Schuchardt (xypron)]

https://salsa.debian.org/grub-team/grub/-/merge_requests/65