Re: [PATCH hyperv-next 0/2] x86/hyperv: VTL mode reboot fixes

[Wei Liu]

On Fri, Jan 17, 2025 at 01:07:00PM -0800, Roman Kisel wrote:
> The first patch defines a specialized machine emergency restart
> callback not to write to the physical address of 0x472 which is
> what the native_machine_emergency_restart() does unconditionally.
> 
> I first wanted to tweak that function[1], and in the course of
> the discussion it looked as the risks of doing that would
> outweigh the benefit: the bare-metal systems have likely adopted
> that behavior as a standard although I could not find any mentions
> of that magic address in the UEFI+ACPI specification.
> 
> The second patch removes the need to always supply "reboot=t"
> to the kernel command line in the OpenHCL bootloader [2]. There is
> no other option at the moment; when/if it appears the newly added
> callback's code can be adjusted as required.
> 
> It would be great to apply this to the stable tree if no concerns,
> should apply cleanly.
> 
> [1] https://lore.kernel.org/all/20250109204352.1720337-1-romank@xxxxxxxxxxxxxxxxxxx/
> [2] https://github.com/microsoft/openvmm/blob/7a9d0e0a00461be6e5f3267af9ea54cc7157c900/openhcl/openhcl_boot/src/main.rs#L139
> 
> Roman Kisel (2):
>   x86/hyperv: VTL mode emergency restart callback
>   x86/hyperv: VTL mode callback for restarting the system

Saurabh please review these patches. Thanks.

I don't have a strong opinion on them.

> 
>  arch/x86/hyperv/hv_vtl.c | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> 
> base-commit: 2e03358be78b65d28b66e17aca9e0c8700b0df78
> -- 
> 2.34.1
>