On Wed, Feb 12, 2025 at 02:21:18AM +0000, Wei Liu wrote:

On Fri, Jan 17, 2025 at 01:07:00PM -0800, Roman Kisel wrote:

quoted

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@linux.microsoft.com/ (local)
[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.

Hi Roman,

Thanks for the patch, few suggestions and queries:

1. Please fix the kernel bot warning
2. Cc Stable tree is not enough, you need to mention the "Fixes" tag as well
   for the commit upto where you want this patch to be backported.
3. In your 2/2 commit, you mention 'triple fault' is the only way to reboot in x86.
   Is that accurate ? Do you mean to say OpenHCL/VTL here ?
   If this behaviour is specific to OpenHCl and not VTLs in general, is there a way
   we can make these changes only for OpenHCL.
   

- Saurabh

I don't have a strong opinion on them.

quoted

 arch/x86/hyperv/hv_vtl.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)


base-commit: 2e03358be78b65d28b66e17aca9e0c8700b0df78
-- 
2.34.1