[Xen-changelog] [xen stable-4.12] x86: make loading of GDT at context switch more modular

[patchbot@xxxxxxx]

commit 122f18afbea526bc949735c37854c33c85dbe2ca
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Fri Jul 19 16:13:19 2019 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Jul 19 16:13:19 2019 +0200

    x86: make loading of GDT at context switch more modular
    
    In preparation for core scheduling, carve out the GDT related
    functionality (writing GDT related PTEs, loading default of full GDT)
    into sub-functions.
    
    Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 12dce7ea5a84e0f107710f8df1cfb2dfe306c793
    master date: 2019-07-04 16:02:52 +0200
---
 xen/arch/x86/domain.c | 57 +++++++++++++++++++++++++++++++--------------------
 1 file changed, 35 insertions(+), 22 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 8d579e2cf9..e07f2b37c7 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1613,6 +1613,37 @@ static inline bool need_full_gdt(const struct domain *d)
     return is_pv_domain(d) && !is_idle_domain(d);
 }
 
+static void write_full_gdt_ptes(seg_desc_t *gdt, const struct vcpu *v)
+{
+    unsigned long mfn = virt_to_mfn(gdt);
+    l1_pgentry_t *pl1e = pv_gdt_ptes(v);
+    unsigned int i;
+
+    for ( i = 0; i < NR_RESERVED_GDT_PAGES; i++ )
+        l1e_write(pl1e + FIRST_RESERVED_GDT_PAGE + i,
+                  l1e_from_pfn(mfn + i, __PAGE_HYPERVISOR_RW));
+}
+
+static void load_full_gdt(const struct vcpu *v, unsigned int cpu)
+{
+    struct desc_ptr gdt_desc = {
+        .limit = LAST_RESERVED_GDT_BYTE,
+        .base = GDT_VIRT_START(v),
+    };
+
+    lgdt(&gdt_desc);
+}
+
+static void load_default_gdt(const seg_desc_t *gdt, unsigned int cpu)
+{
+    struct desc_ptr gdt_desc = {
+        .limit = LAST_RESERVED_GDT_BYTE,
+        .base  = (unsigned long)(gdt - FIRST_RESERVED_GDT_ENTRY),
+    };
+
+    lgdt(&gdt_desc);
+}
+
 static void __context_switch(void)
 {
     struct cpu_user_regs *stack_regs = guest_cpu_user_regs();
@@ -1621,7 +1652,6 @@ static void __context_switch(void)
     struct vcpu          *n = current;
     struct domain        *pd = p->domain, *nd = n->domain;
     seg_desc_t           *gdt;
-    struct desc_ptr       gdt_desc;
 
     ASSERT(p != n);
     ASSERT(!vcpu_cpu_dirty(n));
@@ -1663,25 +1693,13 @@ static void __context_switch(void)
 
     gdt = !is_pv_32bit_domain(nd) ? per_cpu(gdt_table, cpu) :
                                     per_cpu(compat_gdt_table, cpu);
-    if ( need_full_gdt(nd) )
-    {
-        unsigned long mfn = virt_to_mfn(gdt);
-        l1_pgentry_t *pl1e = pv_gdt_ptes(n);
-        unsigned int i;
 
-        for ( i = 0; i < NR_RESERVED_GDT_PAGES; i++ )
-            l1e_write(pl1e + FIRST_RESERVED_GDT_PAGE + i,
-                      l1e_from_pfn(mfn + i, __PAGE_HYPERVISOR_RW));
-    }
+    if ( need_full_gdt(nd) )
+        write_full_gdt_ptes(gdt, n);
 
     if ( need_full_gdt(pd) &&
          ((p->vcpu_id != n->vcpu_id) || !need_full_gdt(nd)) )
-    {
-        gdt_desc.limit = LAST_RESERVED_GDT_BYTE;
-        gdt_desc.base  = (unsigned long)(gdt - FIRST_RESERVED_GDT_ENTRY);
-
-        lgdt(&gdt_desc);
-    }
+        load_default_gdt(gdt, cpu);
 
     write_ptbase(n);
 
@@ -1694,12 +1712,7 @@ static void __context_switch(void)
 
     if ( need_full_gdt(nd) &&
          ((p->vcpu_id != n->vcpu_id) || !need_full_gdt(pd)) )
-    {
-        gdt_desc.limit = LAST_RESERVED_GDT_BYTE;
-        gdt_desc.base = GDT_VIRT_START(n);
-
-        lgdt(&gdt_desc);
-    }
+        load_full_gdt(n, cpu);
 
     if ( pd != nd )
         cpumask_clear_cpu(cpu, pd->dirty_cpumask);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.12

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