Re: [PATCH] x86: machine_restart() must not call acpi_dmar_reinstate() twice

[Keir Fraser <keir.xen@gmail.com>]

On 13/09/2013 01:07, "Jan Beulich" <JBeulich@suse.com> wrote:

> .. as that function is not idempotent (it always alters the table
> checksum). The (generally) duplicate call was a result from it being
> made before machine_restart() re-invoking itself on the boot CPU.
> 
> Considering that no problem arose so far from the table corruption I
> doubt that we need to restore the correct table signature on the
> reboot path in general. The only case I can see this as potentially
> necessary is the tboot one, hence do the call just in that case.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Keir Fraser <keir@xen.org>

> ---
> Note that this was found to be particularly an issue backporting
> 2ee9cbf9 ("ACPI: fix acpi_os_map_memory()") to 4.1.x: The first
> invocation would acquire the lock in acpi_os_map_memory(), and since
> the lock never gets released, the second invocation gets stuck.
> 
> --- a/xen/arch/x86/shutdown.c
> +++ b/xen/arch/x86/shutdown.c
> @@ -470,8 +470,6 @@ void machine_restart(unsigned int delay_
>      console_start_sync();
>      spin_debug_disable();
>  
> -    acpi_dmar_reinstate();
> -
>      local_irq_enable();
>  
>      /* Ensure we are the boot CPU. */
> @@ -496,7 +494,10 @@ void machine_restart(unsigned int delay_
>      mdelay(delay_millisecs);
>  
>      if ( tboot_in_measured_env() )
> +    {
> +        acpi_dmar_reinstate();
>          tboot_shutdown(TB_SHUTDOWN_REBOOT);
> +    }
>  
>      efi_reset_system(reboot_mode != 0);
>  
> 
> 
> 
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