[Xen-changelog] [xen-unstable] x86/hpet: disable before reboot or kexec

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Jan Beulich <jbeulich@xxxxxxxx>
# Date 1332854423 -7200
# Node ID f06ff3dfde08ee563970cffba502742249ff5820
# Parent  ed48258053aea953afd28b746b53af7b8b30531b
x86/hpet: disable before reboot or kexec

Linux up to now is not smart enough to properly clear the HPET when it
boots, which is particularly a problem when a kdump attempt from
running under Xen is being made. Linux itself added code to work around
this to its shutdown paths quite some time ago, so let's do something
similar in Xen: Save the configuration register settings during boot,
and restore them during shutdown. This should cover the majority of
cases where the secondary kernel might not come up because timer
interrupts don't work.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Keir Fraser <keir@xxxxxxx>
---


diff -r ed48258053ae -r f06ff3dfde08 xen/arch/x86/crash.c
--- a/xen/arch/x86/crash.c      Tue Mar 27 11:13:58 2012 +0100
+++ b/xen/arch/x86/crash.c      Tue Mar 27 15:20:23 2012 +0200
@@ -94,6 +94,7 @@ static void nmi_shootdown_cpus(void)
     x2apic_enabled = (current_local_apic_mode() == APIC_MODE_X2APIC);
 
     disable_IO_APIC();
+    hpet_disable();
 }
 
 void machine_crash_shutdown(void)
diff -r ed48258053ae -r f06ff3dfde08 xen/arch/x86/hpet.c
--- a/xen/arch/x86/hpet.c       Tue Mar 27 11:13:58 2012 +0100
+++ b/xen/arch/x86/hpet.c       Tue Mar 27 15:20:23 2012 +0200
@@ -562,7 +562,7 @@ void hpet_broadcast_resume(void)
     if ( !hpet_events )
         return;
 
-    hpet_resume();
+    hpet_resume(NULL);
 
     cfg = hpet_read32(HPET_CFG);
 
@@ -700,10 +700,13 @@ int hpet_legacy_irq_tick(void)
     return 1;
 }
 
+static u32 *hpet_boot_cfg;
+
 u64 __init hpet_setup(void)
 {
     static u64 __initdata hpet_rate;
     u32 hpet_id, hpet_period;
+    unsigned int last;
 
     if ( hpet_rate )
         return hpet_rate;
@@ -728,7 +731,9 @@ u64 __init hpet_setup(void)
         return 0;
     }
 
-    hpet_resume();
+    last = (hpet_id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT;
+    hpet_boot_cfg = xmalloc_array(u32, 2 + last);
+    hpet_resume(hpet_boot_cfg);
 
     hpet_rate = 1000000000000000ULL; /* 10^15 */
     (void)do_div(hpet_rate, hpet_period);
@@ -736,24 +741,29 @@ u64 __init hpet_setup(void)
     return hpet_rate;
 }
 
-void hpet_resume(void)
+void hpet_resume(u32 *boot_cfg)
 {
     static u32 system_reset_latch;
     u32 hpet_id, cfg;
-    unsigned int i;
+    unsigned int i, last;
 
     if ( system_reset_latch == system_reset_counter )
         return;
     system_reset_latch = system_reset_counter;
 
     cfg = hpet_read32(HPET_CFG);
+    if ( boot_cfg )
+        *boot_cfg = cfg;
     cfg &= ~(HPET_CFG_ENABLE | HPET_CFG_LEGACY);
     hpet_write32(cfg, HPET_CFG);
 
     hpet_id = hpet_read32(HPET_ID);
-    for ( i = 0; i <= ((hpet_id >> 8) & 31); i++ )
+    last = (hpet_id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT;
+    for ( i = 0; i <= last; ++i )
     {
         cfg = hpet_read32(HPET_Tn_CFG(i));
+        if ( boot_cfg )
+            boot_cfg[i + 1] = cfg;
         cfg &= ~HPET_TN_ENABLE;
         hpet_write32(cfg, HPET_Tn_CFG(i));
     }
@@ -762,3 +772,21 @@ void hpet_resume(void)
     cfg |= HPET_CFG_ENABLE;
     hpet_write32(cfg, HPET_CFG);
 }
+
+void hpet_disable(void)
+{
+    unsigned int i;
+    u32 id;
+
+    if ( !hpet_boot_cfg )
+        return;
+
+    hpet_write32(*hpet_boot_cfg & ~HPET_CFG_ENABLE, HPET_CFG);
+
+    id = hpet_read32(HPET_ID);
+    for ( i = 0; i <= ((id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT); ++i )
+        hpet_write32(hpet_boot_cfg[i + 1], HPET_Tn_CFG(i));
+
+    if ( *hpet_boot_cfg & HPET_CFG_ENABLE )
+        hpet_write32(*hpet_boot_cfg, HPET_CFG);
+}
diff -r ed48258053ae -r f06ff3dfde08 xen/arch/x86/smp.c
--- a/xen/arch/x86/smp.c        Tue Mar 27 11:13:58 2012 +0100
+++ b/xen/arch/x86/smp.c        Tue Mar 27 15:20:23 2012 +0200
@@ -19,6 +19,7 @@
 #include <asm/mc146818rtc.h>
 #include <asm/flushtlb.h>
 #include <asm/hardirq.h>
+#include <asm/hpet.h>
 #include <asm/hvm/support.h>
 #include <mach_apic.h>
 
@@ -375,6 +376,7 @@ void smp_send_stop(void)
     local_irq_disable();
     __stop_this_cpu();
     disable_IO_APIC();
+    hpet_disable();
     local_irq_enable();
 }
 
diff -r ed48258053ae -r f06ff3dfde08 xen/arch/x86/time.c
--- a/xen/arch/x86/time.c       Tue Mar 27 11:13:58 2012 +0100
+++ b/xen/arch/x86/time.c       Tue Mar 27 15:20:23 2012 +0200
@@ -377,7 +377,7 @@ static int __init init_hpet(struct platf
 
 static void resume_hpet(struct platform_timesource *pts)
 {
-    hpet_resume();
+    hpet_resume(NULL);
 }
 
 static struct platform_timesource __initdata plt_hpet =
diff -r ed48258053ae -r f06ff3dfde08 xen/include/asm-x86/hpet.h
--- a/xen/include/asm-x86/hpet.h        Tue Mar 27 11:13:58 2012 +0100
+++ b/xen/include/asm-x86/hpet.h        Tue Mar 27 15:20:23 2012 +0200
@@ -55,7 +55,12 @@ extern unsigned long hpet_address;
  * Return value is zero if HPET is unavailable.
  */
 u64 hpet_setup(void);
-void hpet_resume(void);
+void hpet_resume(u32 *);
+
+/*
+ * Disable HPET hardware: restore it to boot time state.
+ */
+void hpet_disable(void);
 
 /*
  * Callback from legacy timer (PIT channel 0) IRQ handler.

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