[Xen-changelog] [linux-2.6.18-xen] x86: fix context switch on debug hypervisor after 1183:5e3c342a325e

[Xen patchbot-linux-2.6.18-xen <patchbot@xxxxxxx>]

# HG changeset patch
# User Jan Beulich <jbeulich@xxxxxxxx>
# Date 1344319632 -7200
# Node ID f628814a279a118f4b1b7c121ccc1b8be4d44f9d
# Parent  d5afea2ab44ff42e3a12e3952efa35a60ca2d1de
x86: fix context switch on debug hypervisor after 1183:5e3c342a325e

Looking at anything but the result field of a multicall structure after
issuing the multicall is invalid - the debug hypervisor intentionally
clobbers all other fields.

On i386 also remove some left over, unused debugging code.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---


diff -r d5afea2ab44f -r f628814a279a arch/i386/kernel/process-xen.c
--- a/arch/i386/kernel/process-xen.c    Tue Jul 03 11:07:47 2012 +0200
+++ b/arch/i386/kernel/process-xen.c    Tue Aug 07 08:07:12 2012 +0200
@@ -548,7 +548,7 @@ struct task_struct fastcall * __switch_t
 {
        struct thread_struct *prev = &prev_p->thread,
                                 *next = &next_p->thread;
-       int cpu = smp_processor_id();
+       int cpu = smp_processor_id(), cr0_ts;
 #ifndef CONFIG_X86_NO_TSS
        struct tss_struct *tss = &per_cpu(init_tss, cpu);
 #endif
@@ -575,9 +575,6 @@ struct task_struct fastcall * __switch_t
                mcl->args[0] = 1;
                mcl++;
        }
-#if 0 /* lazy fpu sanity check */
-       else BUG_ON(!(read_cr0() & 8));
-#endif
 
        /*
         * Reload esp0.
@@ -639,11 +636,14 @@ struct task_struct fastcall * __switch_t
        BUG_ON(pdo > _pdo + ARRAY_SIZE(_pdo));
 #endif
        BUG_ON(mcl > _mcl + ARRAY_SIZE(_mcl));
-       if (_mcl->op == __HYPERVISOR_fpu_taskswitch)
+       if (_mcl->op == __HYPERVISOR_fpu_taskswitch) {
                __get_cpu_var(xen_x86_cr0_upd) = X86_CR0_TS;
+               cr0_ts = 1;
+       } else
+               cr0_ts = 0;
        if (unlikely(HYPERVISOR_multicall_check(_mcl, mcl - _mcl, NULL)))
                BUG();
-       if (_mcl->op == __HYPERVISOR_fpu_taskswitch) {
+       if (cr0_ts) {
                __get_cpu_var(xen_x86_cr0) |= X86_CR0_TS;
                xen_clear_cr0_upd();
        }
diff -r d5afea2ab44f -r f628814a279a arch/x86_64/kernel/process-xen.c
--- a/arch/x86_64/kernel/process-xen.c  Tue Jul 03 11:07:47 2012 +0200
+++ b/arch/x86_64/kernel/process-xen.c  Tue Aug 07 08:07:12 2012 +0200
@@ -486,7 +486,7 @@ __switch_to(struct task_struct *prev_p, 
 {
        struct thread_struct *prev = &prev_p->thread,
                                 *next = &next_p->thread;
-       int cpu = smp_processor_id();  
+       int cpu = smp_processor_id(), cr0_ts;
 #ifndef CONFIG_X86_NO_TSS
        struct tss_struct *tss = &per_cpu(init_tss, cpu);
 #endif
@@ -572,11 +572,14 @@ __switch_to(struct task_struct *prev_p, 
        BUG_ON(pdo > _pdo + ARRAY_SIZE(_pdo));
 #endif
        BUG_ON(mcl > _mcl + ARRAY_SIZE(_mcl));
-       if (_mcl->op == __HYPERVISOR_fpu_taskswitch)
+       if (_mcl->op == __HYPERVISOR_fpu_taskswitch) {
                __get_cpu_var(xen_x86_cr0_upd) = X86_CR0_TS;
+               cr0_ts = 1;
+       } else
+               cr0_ts = 0;
        if (unlikely(HYPERVISOR_multicall_check(_mcl, mcl - _mcl, NULL)))
                BUG();
-       if (_mcl->op == __HYPERVISOR_fpu_taskswitch) {
+       if (cr0_ts) {
                __get_cpu_var(xen_x86_cr0) |= X86_CR0_TS;
                xen_clear_cr0_upd();
        }

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