[Xen-devel] [PATCH RFC 07/44] x86/boot: Use percpu pagetables for the idle vcpus

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Introduce early_switch_to_idle() to replace the opencoded switching to idle
context in the BSP and AP boot paths, and extend it to switch away from
idle_pg_table[] as well.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/domain.c        |  4 +++-
 xen/arch/x86/domain_page.c   |  2 +-
 xen/arch/x86/setup.c         | 22 ++++++++++++++++++++--
 xen/arch/x86/smpboot.c       |  6 ++++--
 xen/include/asm-x86/system.h |  1 +
 5 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 0ae715d..93e81c0 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -349,7 +349,9 @@ int vcpu_initialise(struct vcpu *v)
     else
     {
         /* Idle domain */
-        v->arch.cr3 = __pa(idle_pg_table);
+        v->arch.cr3 = per_cpu(percpu_idle_pt, v->vcpu_id);
+        BUG_ON(!v->arch.cr3); /* Had better be initialised... */
+
         rc = 0;
         v->arch.msr = ZERO_BLOCK_PTR; /* Catch stray misuses */
     }
diff --git a/xen/arch/x86/domain_page.c b/xen/arch/x86/domain_page.c
index 3432a85..8f2bcd4 100644
--- a/xen/arch/x86/domain_page.c
+++ b/xen/arch/x86/domain_page.c
@@ -51,7 +51,7 @@ static inline struct vcpu *mapcache_current_vcpu(void)
         if ( (v = idle_vcpu[smp_processor_id()]) == current )
             sync_local_execstate();
         /* We must now be running on the idle page table. */
-        ASSERT(read_cr3() == __pa(idle_pg_table));
+        ASSERT(read_cr3() == this_cpu(percpu_idle_pt));
     }
 
     return v;
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 4aff5bd..b8e52cf 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -237,11 +237,29 @@ void __init discard_initial_images(void)
 
 extern char __init_begin[], __init_end[], __bss_start[], __bss_end[];
 
+void early_switch_to_idle(void)
+{
+    unsigned int cpu = smp_processor_id();
+    struct vcpu *v = idle_vcpu[cpu];
+    unsigned long cr4 = read_cr4();
+
+    set_current(v);
+    per_cpu(curr_vcpu, cpu) = v;
+
+    asm volatile ( "mov %[npge], %%cr4;"
+                   "mov %[cr3], %%cr3;"
+                   "mov %[pge], %%cr4;"
+                   ::
+                    [npge] "r" (cr4 & ~X86_CR4_PGE),
+                    [cr3]  "r" (v->arch.cr3),
+                    [pge]  "r" (cr4)
+                   : "memory" );
+}
+
 static void __init init_idle_domain(void)
 {
     scheduler_init();
-    set_current(idle_vcpu[0]);
-    this_cpu(curr_vcpu) = current;
+    early_switch_to_idle();
 }
 
 void srat_detect_node(int cpu)
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 221d9c7..ae39b48 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -307,8 +307,10 @@ void start_secondary(void *unused)
     /* Critical region without IDT or TSS.  Any fault is deadly! */
 
     set_processor_id(cpu);
-    set_current(idle_vcpu[cpu]);
-    this_cpu(curr_vcpu) = idle_vcpu[cpu];
+    get_cpu_info()->cr4 = XEN_MINIMAL_CR4;
+
+    early_switch_to_idle();
+
     rdmsrl(MSR_EFER, this_cpu(efer));
 
     /*
diff --git a/xen/include/asm-x86/system.h b/xen/include/asm-x86/system.h
index 8ac1703..ee57631 100644
--- a/xen/include/asm-x86/system.h
+++ b/xen/include/asm-x86/system.h
@@ -230,6 +230,7 @@ static inline int local_irq_is_enabled(void)
 
 void trap_init(void);
 void init_idt_traps(void);
+void early_switch_to_idle(void);
 void load_system_tables(void);
 void percpu_traps_init(void);
 void subarch_percpu_traps_init(void);
-- 
2.1.4


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