Re: [PATCH 7 of 7] KEXEC: correctly revert x2apic state when kexecing [Reformatted]

[Andrew Cooper <andrew.cooper3@citrix.com>]

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Tweaked the patch to prevent IOMMU_WAIT_OP panicking on the kexec path. 
Unfortunately, this has to rely on the kexecing variable.

As with the other hacks in this patch, I cant see a better way of
solving the problem.

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com


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KEXEC: correctly revert x2apic state when kexecing

Introduce the boolean variable 'kexecing' which indicates to functions
whether we are on the kexec path or not.  This is used by
disable_local_APIC() to try and revert the APIC mode back to how it
was found on boot.

We also need some fudging of the x2apic_enabled variable.  It is used
in multiple places over the codebase to mean multiple things,
including:
    What did the user specifify on the command line?
    Did the BIOS boot me in x2apic mode?
    Is the BSP Local APIC in x2apic mode?
    What mode is my Local APIC in?

Therefore, set it up to prevent a protection fault when disabling the
IOAPICs.  (In this case, it is used in the "What mode is my Local APIC
in?" case, so the processor doesnt suffer a protection fault because
of trying to use x2apic MSRs when it should be using xapic MMIO)

Finally, make sure that interrupts are disabled when jumping into the
purgatory code.  It would be bad to service interrupts in the Xen
context when the next kernel is booting.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff -r e30942288f87 xen/arch/x86/apic.c
--- a/xen/arch/x86/apic.c	Wed Jun 15 15:55:20 2011 +0100
+++ b/xen/arch/x86/apic.c	Wed Jun 15 16:21:13 2011 +0100
@@ -37,6 +37,7 @@
 #include <asm/asm_defns.h> /* for BUILD_SMP_INTERRUPT */
 #include <mach_apic.h>
 #include <io_ports.h>
+#include <xen/kexec.h>
 
 static bool_t tdt_enabled __read_mostly;
 static bool_t tdt_enable __initdata = 1;
@@ -349,6 +350,33 @@ void disable_local_APIC(void)
         wrmsrl(MSR_IA32_APICBASE, msr_content &
                ~(MSR_IA32_APICBASE_ENABLE|MSR_IA32_APICBASE_EXTD));
     }
+
+    if ( kexecing )
+    {
+        uint64_t msr_content;
+        rdmsrl(MSR_IA32_APICBASE, msr_content);
+        msr_content &= ~(MSR_IA32_APICBASE_ENABLE|MSR_IA32_APICBASE_EXTD);
+        wrmsrl(MSR_IA32_APICBASE, msr_content);
+
+        switch ( apic_boot_mode )
+        {
+        case APIC_MODE_DISABLED:
+            break; /* Nothing to do - we did this above */
+        case APIC_MODE_XAPIC:
+            msr_content |= MSR_IA32_APICBASE_ENABLE;
+            wrmsrl(MSR_IA32_APICBASE, msr_content);
+            break;
+        case APIC_MODE_X2APIC:
+            msr_content |= (MSR_IA32_APICBASE_ENABLE|MSR_IA32_APICBASE_EXTD);
+            wrmsrl(MSR_IA32_APICBASE, msr_content);
+            break;
+        default:
+            printk("Default case when reverting #%d lapic to boot state\n",
+                   smp_processor_id());
+            break;
+        }
+    }
+
 }
 
 /*
diff -r e30942288f87 xen/arch/x86/crash.c
--- a/xen/arch/x86/crash.c	Wed Jun 15 15:55:20 2011 +0100
+++ b/xen/arch/x86/crash.c	Wed Jun 15 16:21:13 2011 +0100
@@ -27,6 +27,7 @@
 #include <asm/hvm/support.h>
 #include <asm/apic.h>
 #include <asm/io_apic.h>
+#include <xen/iommu.h>
 
 static atomic_t waiting_for_crash_ipi;
 static unsigned int crashing_cpu;
@@ -82,6 +83,15 @@ static void nmi_shootdown_cpus(void)
     iommu_crash_shutdown();
 
     __stop_this_cpu();
+
+    /* This is a bit of a hack due to the problems with the x2apic_enabled
+     * variable, but we can't do any better without a significant refactoring
+     * of the APIC code */
+    if ( current_local_apic_mode() == APIC_MODE_X2APIC )
+        x2apic_enabled = 1;
+    else
+        x2apic_enabled = 0;
+
     disable_IO_APIC();
 }
 
diff -r e30942288f87 xen/arch/x86/machine_kexec.c
--- a/xen/arch/x86/machine_kexec.c	Wed Jun 15 15:55:20 2011 +0100
+++ b/xen/arch/x86/machine_kexec.c	Wed Jun 15 16:21:13 2011 +0100
@@ -88,6 +88,11 @@ void machine_kexec(xen_kexec_image_t *im
     if ( hpet_broadcast_is_available() )
         hpet_disable_legacy_broadcast();
 
+    /* We are about to permenantly jump out of the Xen context into the kexec
+     * purgatory code.  We really dont want to be still servicing interupts.
+     */
+    local_irq_disable();
+
     /*
      * compat_machine_kexec() returns to idle pagetables, which requires us
      * to be running on a static GDT mapping (idle pagetables have no GDT
diff -r e30942288f87 xen/common/kexec.c
--- a/xen/common/kexec.c	Wed Jun 15 15:55:20 2011 +0100
+++ b/xen/common/kexec.c	Wed Jun 15 16:21:13 2011 +0100
@@ -29,6 +29,8 @@
 #include <compat/kexec.h>
 #endif
 
+bool_t kexecing = FALSE;
+
 static DEFINE_PER_CPU_READ_MOSTLY(void *, crash_notes);
 
 static Elf_Note *xen_crash_note;
@@ -220,6 +222,8 @@ void kexec_crash(void)
     if ( !test_bit(KEXEC_IMAGE_CRASH_BASE + pos, &kexec_flags) )
         return;
 
+    kexecing = TRUE;
+
     kexec_common_shutdown();
     kexec_crash_save_cpu();
     machine_crash_shutdown();
@@ -232,6 +236,8 @@ static long kexec_reboot(void *_image)
 {
     xen_kexec_image_t *image = _image;
 
+    kexecing = TRUE;
+
     kexec_common_shutdown();
     machine_reboot_kexec(image);
 
diff -r e30942288f87 xen/drivers/passthrough/vtd/dmar.h
--- a/xen/drivers/passthrough/vtd/dmar.h	Wed Jun 15 15:55:20 2011 +0100
+++ b/xen/drivers/passthrough/vtd/dmar.h	Wed Jun 15 16:21:13 2011 +0100
@@ -23,6 +23,7 @@
 
 #include <xen/list.h>
 #include <xen/iommu.h>
+#include <xen/kexec.h>
 
 /* This one is for interrupt remapping */
 struct acpi_ioapic_unit {
@@ -99,8 +100,9 @@ do {                                    
         if ( cond )                                 \
             break;                                  \
         if ( NOW() > start_time + DMAR_OPERATION_TIMEOUT )      \
-            panic("%s:%d:%s: DMAR hardware is malfunctional\n", \
-                  __FILE__, __LINE__, __func__);                \
+            if ( !kexecing )                                    \
+                panic("%s:%d:%s: DMAR hardware is malfunctional\n",\
+                      __FILE__, __LINE__, __func__);            \
         cpu_relax();                                            \
     }                                                           \
 } while (0)
diff -r e30942288f87 xen/include/xen/kexec.h
--- a/xen/include/xen/kexec.h	Wed Jun 15 15:55:20 2011 +0100
+++ b/xen/include/xen/kexec.h	Wed Jun 15 16:21:13 2011 +0100
@@ -12,6 +12,8 @@ typedef struct xen_kexec_reserve {
 
 extern xen_kexec_reserve_t kexec_crash_area;
 
+extern bool_t kexecing;
+
 void set_kexec_crash_area_size(u64 system_ram);
 
 /* We have space for 4 images to support atomic update

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