[Xen-devel] [PATCH RFC 23/44] x86/smp: Allocate percpu resources for map_domain_page() to use

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The mapcache infrastructure needs some linear address space with which to make
temporary mappings.

_alter_percpu_mappings() is updated to support allocating an L1t, and
cpu_smpboot_alloc_common() is updated to allocate an L1t for mapcache
purposes, and map the L1t into linear address space so it can be easily
modified.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/smpboot.c       | 27 ++++++++++++++++++++++++++-
 xen/include/asm-x86/config.h |  4 ++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 7f02dd8..6a5f18a 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -645,6 +645,7 @@ void cpu_exit_clear(unsigned int cpu)
  */
 enum percpu_alter_action {
     PERCPU_MAP, /* Map existing frame: page and flags are input parameters. */
+    PERCPU_ALLOC_L1T, /* Allocate an L1 table. optionally returned via *page. 
*/
 };
 static int _alter_percpu_mappings(
     unsigned int cpu, unsigned long linear,
@@ -694,7 +695,10 @@ static int _alter_percpu_mappings(
         l2t[l2_table_offset(linear)] = l2e_from_page(pg, __PAGE_HYPERVISOR);
     }
     else
-        l1t = map_l1t_from_l2e(l2t[l2_table_offset(linear)]);
+    {
+        pg = l2e_get_page(l2t[l2_table_offset(linear)]);
+        l1t = __map_domain_page(pg);
+    }
 
     switch ( action )
     {
@@ -703,6 +707,11 @@ static int _alter_percpu_mappings(
         l1t[l1_table_offset(linear)] = l1e_from_page(*page, flags);
         break;
 
+    case PERCPU_ALLOC_L1T:
+        if ( page )
+            *page = pg;
+        break;
+
     default:
         ASSERT_UNREACHABLE();
         rc = -EINVAL;
@@ -727,6 +736,12 @@ static int percpu_map_frame(unsigned int cpu, unsigned 
long linear,
     return _alter_percpu_mappings(cpu, linear, PERCPU_MAP, &page, flags);
 }
 
+static int percpu_alloc_l1t(unsigned int cpu, unsigned long linear,
+                            struct page_info **page)
+{
+    return _alter_percpu_mappings(cpu, linear, PERCPU_ALLOC_L1T, page, 0);
+}
+
 /* Allocate data common between the BSP and APs. */
 static int cpu_smpboot_alloc_common(unsigned int cpu)
 {
@@ -770,6 +785,16 @@ static int cpu_smpboot_alloc_common(unsigned int cpu)
     if ( rc )
         goto out;
 
+    /* Allocate space for the mapcache L1e's... */
+    rc = percpu_alloc_l1t(cpu, PERCPU_MAPCACHE_START, &pg);
+    if ( rc )
+        goto out;
+
+    /* ... and map the L1t so it can be used. */
+    rc = percpu_map_frame(cpu, PERCPU_MAPCACHE_L1ES, pg, PAGE_HYPERVISOR_RW);
+    if ( rc )
+        goto out;
+
     rc = 0; /* Success */
 
  out:
diff --git a/xen/include/asm-x86/config.h b/xen/include/asm-x86/config.h
index cddfc4e..a95f8c8 100644
--- a/xen/include/asm-x86/config.h
+++ b/xen/include/asm-x86/config.h
@@ -296,6 +296,10 @@ extern unsigned long xen_phys_start;
 /* Mappings in the percpu area: */
 #define PERCPU_IDT_MAPPING       (PERCPU_LINEAR_START + KB(4))
 
+#define PERCPU_MAPCACHE_L1ES     (PERCPU_LINEAR_START + MB(2) + KB(12))
+#define PERCPU_MAPCACHE_START    (PERCPU_LINEAR_START + MB(4))
+#define PERCPU_MAPCACHE_END      (PERCPU_MAPCACHE_START + MB(2))
+
 /* GDT/LDT shadow mapping area. The first per-domain-mapping sub-area. */
 #define GDT_LDT_VCPU_SHIFT       5
 #define GDT_LDT_VCPU_VA_SHIFT    (GDT_LDT_VCPU_SHIFT + PAGE_SHIFT)
-- 
2.1.4


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