[PATCH RFC 27/44] x86/smp: Allocate a percpu linear range for the compat translation area.

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

The existing translation area claims to be 2 frames and a guard page, but is
actually 4 frames with no guard page at all.

Allocate 2 frames in the percpu area, which actually has unmapped frames on
either side.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
 xen/arch/x86/smpboot.c       | 27 +++++++++++++++++++++++++++
 xen/include/asm-x86/config.h |  2 ++
 2 files changed, 29 insertions(+)

diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 6a5f18a..a5d3f7a 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -646,6 +646,8 @@ 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. */
+    PERCPU_ALLOC_FRAME, /* Allocate a frame. flags is an input, and *page is
+                         * optionally an output. */
 };
 static int _alter_percpu_mappings(
     unsigned int cpu, unsigned long linear,
@@ -707,6 +709,15 @@ static int _alter_percpu_mappings(
         l1t[l1_table_offset(linear)] = l1e_from_page(*page, flags);
         break;
 
+    case PERCPU_ALLOC_FRAME:
+        pg = alloc_domheap_page(NULL, memflags);
+        if ( !pg )
+            goto out;
+
+        clear_domain_page(page_to_mfn(pg));
+        l1t[l1_table_offset(linear)] = l1e_from_page(pg, flags);
+
+        /* Fallthrough */
     case PERCPU_ALLOC_L1T:
         if ( page )
             *page = pg;
@@ -742,6 +753,12 @@ static int percpu_alloc_l1t(unsigned int cpu, unsigned long linear,
     return _alter_percpu_mappings(cpu, linear, PERCPU_ALLOC_L1T, page, 0);
 }
 
+static int percpu_alloc_frame(unsigned int cpu, unsigned long linear,
+                              struct page_info **page, unsigned int flags)
+{
+    return _alter_percpu_mappings(cpu, linear, PERCPU_ALLOC_FRAME, page, flags);
+}
+
 /* Allocate data common between the BSP and APs. */
 static int cpu_smpboot_alloc_common(unsigned int cpu)
 {
@@ -795,6 +812,16 @@ static int cpu_smpboot_alloc_common(unsigned int cpu)
     if ( rc )
         goto out;
 
+    /* Allocate two pages for the XLAT area. */
+    rc = percpu_alloc_frame(cpu, PERCPU_XLAT_START, NULL,
+                            PAGE_HYPERVISOR_RW | MAP_PERCPU_AUTOFREE);
+    if ( rc )
+        goto out;
+    rc = percpu_alloc_frame(cpu, PERCPU_XLAT_START + PAGE_SIZE, NULL,
+                            PAGE_HYPERVISOR_RW | MAP_PERCPU_AUTOFREE);
+    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 f78cbde..3d64047 100644
--- a/xen/include/asm-x86/config.h
+++ b/xen/include/asm-x86/config.h
@@ -300,6 +300,8 @@ extern unsigned long xen_phys_start;
 #define PERCPU_MAPCACHE_START    (PERCPU_LINEAR_START + MB(4))
 #define PERCPU_MAPCACHE_END      (PERCPU_MAPCACHE_START + MB(2))
 
+#define PERCPU_XLAT_START        (PERCPU_LINEAR_START + MB(6) + KB(8))
+
 /* 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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