[PATCH RFC 02/44] x86/idt: Factor out enabling and disabling of ISTs

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

All alteration of IST settings (other than the crash path) happen in an
identical triple.  Introduce helpers to keep the triple in sync, and reduce
the risk of opencoded mistakes.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
 xen/arch/x86/cpu/common.c       |  4 +---
 xen/arch/x86/hvm/svm/svm.c      |  8 ++------
 xen/arch/x86/smpboot.c          |  4 +---
 xen/arch/x86/traps.c            |  4 +---
 xen/include/asm-x86/processor.h | 14 ++++++++++++++
 5 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index e9588b3..b18e0f4 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -703,9 +703,7 @@ void load_system_tables(void)
 	ltr(TSS_ENTRY << 3);
 	lldt(0);
 
-	set_ist(&idt_tables[cpu][TRAP_double_fault],  IST_DF);
-	set_ist(&idt_tables[cpu][TRAP_nmi],	      IST_NMI);
-	set_ist(&idt_tables[cpu][TRAP_machine_check], IST_MCE);
+	enable_each_ist(idt_tables[cpu]);
 
 	/*
 	 * Bottom-of-stack must be 16-byte aligned!
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 2e62b9b..7bfb0ba 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -1038,9 +1038,7 @@ static void svm_ctxt_switch_from(struct vcpu *v)
     svm_vmload_pa(per_cpu(host_vmcb, cpu));
 
     /* Resume use of ISTs now that the host TR is reinstated. */
-    set_ist(&idt_tables[cpu][TRAP_double_fault],  IST_DF);
-    set_ist(&idt_tables[cpu][TRAP_nmi],           IST_NMI);
-    set_ist(&idt_tables[cpu][TRAP_machine_check], IST_MCE);
+    enable_each_ist(idt_tables[cpu]);
 }
 
 static void svm_ctxt_switch_to(struct vcpu *v)
@@ -1059,9 +1057,7 @@ static void svm_ctxt_switch_to(struct vcpu *v)
      * Cannot use ISTs for NMI/#MC/#DF while we are running with the guest TR.
      * But this doesn't matter: the IST is only req'd to handle SYSCALL/SYSRET.
      */
-    set_ist(&idt_tables[cpu][TRAP_double_fault],  IST_NONE);
-    set_ist(&idt_tables[cpu][TRAP_nmi],           IST_NONE);
-    set_ist(&idt_tables[cpu][TRAP_machine_check], IST_NONE);
+    disable_each_ist(idt_tables[cpu]);
 
     svm_restore_dr(v);
 
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 7b97ff8..e7fa159 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -723,9 +723,7 @@ static int cpu_smpboot_alloc(unsigned int cpu)
     if ( idt_tables[cpu] == NULL )
         goto out;
     memcpy(idt_tables[cpu], idt_table, IDT_ENTRIES * sizeof(idt_entry_t));
-    set_ist(&idt_tables[cpu][TRAP_double_fault],  IST_NONE);
-    set_ist(&idt_tables[cpu][TRAP_nmi],           IST_NONE);
-    set_ist(&idt_tables[cpu][TRAP_machine_check], IST_NONE);
+    disable_each_ist(idt_tables[cpu]);
 
     for ( stub_page = 0, i = cpu & ~(STUBS_PER_PAGE - 1);
           i < nr_cpu_ids && i <= (cpu | (STUBS_PER_PAGE - 1)); ++i )
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index db16a44..d06ad69 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1884,9 +1884,7 @@ void __init init_idt_traps(void)
     set_intr_gate(TRAP_simd_error,&simd_coprocessor_error);
 
     /* Specify dedicated interrupt stacks for NMI, #DF, and #MC. */
-    set_ist(&idt_table[TRAP_double_fault],  IST_DF);
-    set_ist(&idt_table[TRAP_nmi],           IST_NMI);
-    set_ist(&idt_table[TRAP_machine_check], IST_MCE);
+    enable_each_ist(idt_table);
 
     /* CPU0 uses the master IDT. */
     idt_tables[0] = idt_table;
diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index 41a8d8c..a0c524b 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -457,6 +457,20 @@ static always_inline void set_ist(idt_entry_t *idt, unsigned long ist)
     _write_gate_lower(idt, &new);
 }
 
+static inline void enable_each_ist(idt_entry_t *idt)
+{
+    set_ist(&idt[TRAP_double_fault],  IST_DF);
+    set_ist(&idt[TRAP_nmi],           IST_NMI);
+    set_ist(&idt[TRAP_machine_check], IST_MCE);
+}
+
+static inline void disable_each_ist(idt_entry_t *idt)
+{
+    set_ist(&idt[TRAP_double_fault],  IST_NONE);
+    set_ist(&idt[TRAP_nmi],           IST_NONE);
+    set_ist(&idt[TRAP_machine_check], IST_NONE);
+}
+
 #define IDT_ENTRIES 256
 extern idt_entry_t idt_table[];
 extern idt_entry_t *idt_tables[];
-- 
2.1.4


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