Re: [PATCH v2] x86/shutdown: change default reboot method preference

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Fri, Sep 15, 2023 at 09:43:47AM +0200, Roger Pau Monne wrote:
> The current logic to chose the preferred reboot method is based on the mode Xen
> has been booted into, so if the box is booted from UEFI, the preferred reboot
> method will be to use the ResetSystem() run time service call.
> 
> However, that method seems to be widely untested, and quite often leads to a
> result similar to:
> 
> Hardware Dom0 shutdown: rebooting machine
> ----[ Xen-4.18-unstable  x86_64  debug=y  Tainted:   C    ]----
> CPU:    0
> RIP:    e008:[<0000000000000017>] 0000000000000017
> RFLAGS: 0000000000010202   CONTEXT: hypervisor
> [...]
> Xen call trace:
>    [<0000000000000017>] R 0000000000000017
>    [<ffff83207eff7b50>] S ffff83207eff7b50
>    [<ffff82d0403525aa>] F machine_restart+0x1da/0x261
>    [<ffff82d04035263c>] F apic_wait_icr_idle+0/0x37
>    [<ffff82d040233689>] F smp_call_function_interrupt+0xc7/0xcb
>    [<ffff82d040352f05>] F call_function_interrupt+0x20/0x34
>    [<ffff82d04033b0d5>] F do_IRQ+0x150/0x6f3
>    [<ffff82d0402018c2>] F common_interrupt+0x132/0x140
>    [<ffff82d040283d33>] F arch/x86/acpi/cpu_idle.c#acpi_idle_do_entry+0x113/0x129
>    [<ffff82d04028436c>] F arch/x86/acpi/cpu_idle.c#acpi_processor_idle+0x3eb/0x5f7
>    [<ffff82d04032a549>] F arch/x86/domain.c#idle_loop+0xec/0xee
> 
> ****************************************
> Panic on CPU 0:
> FATAL TRAP: vector = 6 (invalid opcode)
> ****************************************
> 
> Which in most cases does lead to a reboot, however that's unreliable.
> 
> Change the default reboot preference to prefer ACPI over UEFI if available and
> not in reduced hardware mode.
> 
> This is in line to what Linux does, so it's unlikely to cause issues on current
> and future hardware, since there's a much higher chance of vendors testing
> hardware with Linux rather than Xen.
> 
> Add a special case for one Acer model that does require being rebooted using
> ResetSystem().  See Linux commit 0082517fa4bce for rationale.
> 
> I'm not aware of using ACPI reboot causing issues on boxes that do have
> properly implemented ResetSystem() methods.

With the Acer quirk, and the info Jan posted in the thread, this
sentence technically is not true. I don't think it warrants any code
change in this patch (it's clearly less common and less problematic
issue than crash during ResetSystem(), and still can be worked around
with a cmdline option). But might warrant adjusting commit message.

> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Other points still stand, and I think this generally is an improvement,
so, preferably with adjusted commit message:

Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

> ---
> Changes since v1:
>  - Add special case for Acer model to use UEFI reboot.
>  - Adjust commit message.
> ---
>  xen/arch/x86/shutdown.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/x86/shutdown.c b/xen/arch/x86/shutdown.c
> index 7619544d14da..3816ede1afe5 100644
> --- a/xen/arch/x86/shutdown.c
> +++ b/xen/arch/x86/shutdown.c
> @@ -150,19 +150,20 @@ static void default_reboot_type(void)
>  
>      if ( xen_guest )
>          reboot_type = BOOT_XEN;
> +    else if ( !acpi_disabled && !acpi_gbl_reduced_hardware )
> +        reboot_type = BOOT_ACPI;
>      else if ( efi_enabled(EFI_RS) )
>          reboot_type = BOOT_EFI;
> -    else if ( acpi_disabled )
> -        reboot_type = BOOT_KBD;
>      else
> -        reboot_type = BOOT_ACPI;
> +        reboot_type = BOOT_KBD;
>  }
>  
>  static int __init cf_check override_reboot(const struct dmi_system_id *d)
>  {
>      enum reboot_type type = (long)d->driver_data;
>  
> -    if ( type == BOOT_ACPI && acpi_disabled )
> +    if ( (type == BOOT_ACPI && acpi_disabled) ||
> +         (type == BOOT_EFI && !efi_enabled(EFI_RS)) )
>          type = BOOT_KBD;
>  
>      if ( reboot_type != type )
> @@ -172,6 +173,7 @@ static int __init cf_check override_reboot(const struct dmi_system_id *d)
>              [BOOT_KBD]  = "keyboard controller",
>              [BOOT_ACPI] = "ACPI",
>              [BOOT_CF9]  = "PCI",
> +            [BOOT_EFI]  = "UEFI",
>          };
>  
>          reboot_type = type;
> @@ -530,6 +532,15 @@ static const struct dmi_system_id __initconstrel reboot_dmi_table[] = {
>              DMI_MATCH(DMI_PRODUCT_NAME, "PowerEdge R740"),
>          },
>      },
> +    {    /* Handle problems with rebooting on Acer TravelMate X514-51T. */
> +        .callback = override_reboot,
> +        .driver_data = (void *)(long)BOOT_EFI,
> +        .ident = "Acer TravelMate X514-51T",
> +        .matches = {
> +            DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
> +            DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate X514-51T"),
> +        },
> +    },
>      { }
>  };
>  
> -- 
> 2.42.0
> 
> 

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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