[Xen-devel] [PATCH RFC] efi: By default use the BOOT_ACPI method instead of BOOT_EFI unless on reduced ACPI hardware.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

This mimics the behavior of the Linux kernel in which the reboot
sequence by default under EFI booted kernels is first ACPI.

EFI reboot is only tried if the user supplied it or if the hardware
is an ACPI 5.0 (or higher) reduced hardware board.

This fixes the EFI firmware crashing on Lenovo ThinkCentre M57

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 docs/misc/xen-command-line.markdown |  5 ++++-
 xen/arch/x86/shutdown.c             | 17 +++++++++++++----
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown 
b/docs/misc/xen-command-line.markdown
index a061aa4..f037e0f 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -1099,7 +1099,7 @@ The following resources are available:
   * `rmid_max` indicates the max value for rmid.
 
 ### reboot
-> `= t[riple] | k[bd] | a[cpi] | p[ci] | n[o] [, [w]arm | [c]old]`
+> `= t[riple] | k[bd] | a[cpi] | p[ci] | n[o] | [e]fi [, [w]arm | [c]old]`
 
 > Default: `0`
 
@@ -1119,6 +1119,9 @@ Specify the host reboot method.
 
 `pci` instructs Xen to reboot the host using PCI reset register (port CF9).
 
+'efi' instructs Xen to reboot using the EFI reboot call (in EFI mode by
+ default it will use ACPI method first).
+
 ### sched
 > `= credit | credit2 | sedf | arinc653`
 
diff --git a/xen/arch/x86/shutdown.c b/xen/arch/x86/shutdown.c
index 21f6cf5..f17ae9b 100644
--- a/xen/arch/x86/shutdown.c
+++ b/xen/arch/x86/shutdown.c
@@ -32,12 +32,13 @@ enum reboot_type {
         BOOT_KBD = 'k',
         BOOT_ACPI = 'a',
         BOOT_CF9 = 'p',
+        BOOT_EFI = 'e',
 };
 
 static int reboot_mode;
 
 /*
- * reboot=t[riple] | k[bd] | a[cpi] | p[ci] | n[o] [, [w]arm | [c]old]
+ * reboot=t[riple] | k[bd] | a[cpi] | p[ci] | n[o] | [e]fi [, [w]arm | [c]old]
  * warm   Don't set the cold reboot flag
  * cold   Set the cold reboot flag
  * no     Suppress automatic reboot after panics or crashes
@@ -45,6 +46,7 @@ static int reboot_mode;
  * kbd    Use the keyboard controller. cold reset (default)
  * acpi   Use the RESET_REG in the FADT
  * pci    Use the so-called "PCI reset register", CF9
+ * efi    Use the EFI reboot (if running under EFI)
  */
 static enum reboot_type reboot_type = BOOT_ACPI;
 static void __init set_reboot_type(char *str)
@@ -66,6 +68,7 @@ static void __init set_reboot_type(char *str)
         case 'k':
         case 't':
         case 'p':
+        case 'e':
             reboot_type = *str;
             break;
         }
@@ -452,7 +455,11 @@ static struct dmi_system_id __initdata reboot_dmi_table[] 
= {
 
 static int __init reboot_init(void)
 {
-    dmi_check_system(reboot_dmi_table);
+    int rv;
+
+    rv = dmi_check_system(reboot_dmi_table);
+    if ( !rv && acpi_gbl_reduced_hardware )
+        reboot_type = BOOT_EFI;
     return 0;
 }
 __initcall(reboot_init);
@@ -504,8 +511,6 @@ void machine_restart(unsigned int delay_millisecs)
         tboot_shutdown(TB_SHUTDOWN_REBOOT);
     }
 
-    efi_reset_system(reboot_mode != 0);
-
     /* Rebooting needs to touch the page at absolute address 0. */
     *((unsigned short *)__va(0x472)) = reboot_mode;
 
@@ -532,6 +537,10 @@ void machine_restart(unsigned int delay_millisecs)
             reboot_type = (((attempt == 1) && (orig_reboot_type == BOOT_ACPI))
                            ? BOOT_ACPI : BOOT_TRIPLE);
             break;
+        case BOOT_EFI:
+            efi_reset_system(reboot_mode != 0);
+            reboot_type = BOOT_ACPI;
+            break;
         case BOOT_TRIPLE:
             asm volatile ("lidt %0; int3" : : "m" (no_idt));
             reboot_type = BOOT_KBD;
-- 
2.1.0


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