[PATCH RFC 15/44] x86: Rearrange the virtual layout to introduce a PERCPU linear slot

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

The PERCPU linear range lives in slot 257, and all later slots slide along to
make room.  The size of the directmap is reduced by one slot temporarily.

Later changes will remove the PERDOMAIN slot, at which point the latter slots
will slide back to fill the hole, and end up where they are now.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
 xen/arch/x86/mm.c            | 13 +++++++++----
 xen/include/asm-x86/config.h | 45 +++++++++++++++++++++++++++-----------------
 2 files changed, 37 insertions(+), 21 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index d6f88ca..deff4eb 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -1576,25 +1576,30 @@ void init_xen_l4_slots(l4_pgentry_t *l4t, mfn_t l4mfn,
         ro_mpt ? idle_pg_table[l4_table_offset(RO_MPT_VIRT_START)]
                : l4e_empty();
 
-    /* Slot 257: PCI MMCFG. */
+    /* Slot 257: Per-CPU mappings (filled on context switch). */
+    l4t[l4_table_offset(PERCPU_LINEAR_START)] = l4e_empty();
+
+    /* Slot 258: PCI MMCFG. */
     l4t[l4_table_offset(PCI_MCFG_VIRT_START)] =
         idle_pg_table[l4_table_offset(PCI_MCFG_VIRT_START)];
 
-    /* Slot 258: Self linear mappings. */
+    /* Slot 259: Self linear mappings. */
     ASSERT(!mfn_eq(l4mfn, INVALID_MFN));
     l4t[l4_table_offset(LINEAR_PT_VIRT_START)] =
         l4e_from_mfn(l4mfn, __PAGE_HYPERVISOR_RW);
 
-    /* Slot 259: Shadow linear mappings (if applicable) .*/
+    /* Slot 260: Shadow linear mappings (if applicable). */
     l4t[l4_table_offset(SH_LINEAR_PT_VIRT_START)] =
         mfn_eq(sl4mfn, INVALID_MFN) ? l4e_empty() :
         l4e_from_mfn(sl4mfn, __PAGE_HYPERVISOR_RW);
 
-    /* Slot 260: Per-domain mappings (if applicable). */
+    /* Slot 261: Per-domain mappings (if applicable). */
     l4t[l4_table_offset(PERDOMAIN_VIRT_START)] =
         d ? l4e_from_page(d->arch.perdomain_l3_pg, __PAGE_HYPERVISOR_RW)
           : l4e_empty();
 
+    /* !!! WARNING - TEMPORARILY STALE BELOW !!! */
+
     /* Slot 261-: text/data/bss, RW M2P, vmap, frametable, directmap. */
 #ifndef NDEBUG
     if ( short_directmap &&
diff --git a/xen/include/asm-x86/config.h b/xen/include/asm-x86/config.h
index 9ef9d03..baf973a 100644
--- a/xen/include/asm-x86/config.h
+++ b/xen/include/asm-x86/config.h
@@ -124,13 +124,16 @@ extern unsigned char boot_edid_info[128];
  *  0xffff804000000000 - 0xffff807fffffffff [256GB, 2^38 bytes, PML4:256]
  *    Reserved for future shared info with the guest OS (GUEST ACCESSIBLE).
  *  0xffff808000000000 - 0xffff80ffffffffff [512GB, 2^39 bytes, PML4:257]
- *    ioremap for PCI mmconfig space
+ *    Per-CPU mappings (Xen's GDT/IDT/Stack etc.)
  *  0xffff810000000000 - 0xffff817fffffffff [512GB, 2^39 bytes, PML4:258]
- *    Guest linear page table.
+ *    ioremap for PCI mmconfig space
  *  0xffff818000000000 - 0xffff81ffffffffff [512GB, 2^39 bytes, PML4:259]
- *    Shadow linear page table.
+ *    Guest linear page table.
  *  0xffff820000000000 - 0xffff827fffffffff [512GB, 2^39 bytes, PML4:260]
- *    Per-domain mappings (e.g., GDT, LDT).
+ *    Shadow linear page table.
+ *
+ *                !!! WARNING - TEMPORARILY STALE BELOW !!!
+ *
  *  0xffff828000000000 - 0xffff82bfffffffff [256GB, 2^38 bytes, PML4:261]
  *    Machine-to-phys translation table.
  *  0xffff82c000000000 - 0xffff82cfffffffff [64GB,  2^36 bytes, PML4:261]
@@ -170,6 +173,8 @@ extern unsigned char boot_edid_info[128];
  *    Read-only machine-to-phys translation table (GUEST ACCESSIBLE).
  *  0x0000000100000000 - 0x00007fffffffffff [128TB-4GB,         PML4:0-255]
  *    Unused / Reserved for future use.
+ *
+ *                   !!! WARNING - TEMPORARILY STALE !!!
  */
 
 
@@ -187,26 +192,32 @@ extern unsigned char boot_edid_info[128];
 #define RO_MPT_VIRT_START       (PML4_ADDR(256))
 #define MPT_VIRT_SIZE           (PML4_ENTRY_BYTES / 2)
 #define RO_MPT_VIRT_END         (RO_MPT_VIRT_START + MPT_VIRT_SIZE)
-/* Slot 257: ioremap for PCI mmconfig space for 2048 segments (512GB)
+/* Slot 257: Per-CPU mappings. */
+#define PERCPU_LINEAR_START     (PML4_ADDR(257))
+#define PERCPU_LINEAR_END       (PERCPU_LINEAR_START + PML4_ENTRY_BYTES)
+/* Slot 258: ioremap for PCI mmconfig space for 2048 segments (512GB)
  *     - full 16-bit segment support needs 44 bits
  *     - since PML4 slot has 39 bits, we limit segments to 2048 (11-bits)
  */
-#define PCI_MCFG_VIRT_START     (PML4_ADDR(257))
+#define PCI_MCFG_VIRT_START     (PML4_ADDR(258))
 #define PCI_MCFG_VIRT_END       (PCI_MCFG_VIRT_START + PML4_ENTRY_BYTES)
-/* Slot 258: linear page table (guest table). */
-#define LINEAR_PT_VIRT_START    (PML4_ADDR(258))
+/* Slot 259: linear page table (guest table). */
+#define LINEAR_PT_VIRT_START    (PML4_ADDR(259))
 #define LINEAR_PT_VIRT_END      (LINEAR_PT_VIRT_START + PML4_ENTRY_BYTES)
-/* Slot 259: linear page table (shadow table). */
-#define SH_LINEAR_PT_VIRT_START (PML4_ADDR(259))
+/* Slot 260: linear page table (shadow table). */
+#define SH_LINEAR_PT_VIRT_START (PML4_ADDR(260))
 #define SH_LINEAR_PT_VIRT_END   (SH_LINEAR_PT_VIRT_START + PML4_ENTRY_BYTES)
-/* Slot 260: per-domain mappings (including map cache). */
-#define PERDOMAIN_VIRT_START    (PML4_ADDR(260))
+/* Slot 261: per-domain mappings (including map cache). */
+#define PERDOMAIN_VIRT_START    (PML4_ADDR(261))
 #define PERDOMAIN_SLOT_MBYTES   (PML4_ENTRY_BYTES >> (20 + PAGETABLE_ORDER))
 #define PERDOMAIN_SLOTS         3
 #define PERDOMAIN_VIRT_SLOT(s)  (PERDOMAIN_VIRT_START + (s) * \
                                  (PERDOMAIN_SLOT_MBYTES << 20))
+/*
+ *                !!! WARNING - TEMPORARILY STALE BELOW !!!
+ */
 /* Slot 261: machine-to-phys conversion table (256GB). */
-#define RDWR_MPT_VIRT_START     (PML4_ADDR(261))
+#define RDWR_MPT_VIRT_START     (PML4_ADDR(262))
 #define RDWR_MPT_VIRT_END       (RDWR_MPT_VIRT_START + MPT_VIRT_SIZE)
 /* Slot 261: vmap()/ioremap()/fixmap area (64GB). */
 #define VMAP_VIRT_START         RDWR_MPT_VIRT_END
@@ -234,12 +245,12 @@ extern unsigned char boot_edid_info[128];
 
 #ifndef CONFIG_BIGMEM
 /* Slot 262-271/510: A direct 1:1 mapping of all of physical memory. */
-#define DIRECTMAP_VIRT_START    (PML4_ADDR(262))
-#define DIRECTMAP_SIZE          (PML4_ENTRY_BYTES * (511 - 262))
+#define DIRECTMAP_VIRT_START    (PML4_ADDR(263))
+#define DIRECTMAP_SIZE          (PML4_ENTRY_BYTES * (511 - 263))
 #else
 /* Slot 265-271/510: A direct 1:1 mapping of all of physical memory. */
-#define DIRECTMAP_VIRT_START    (PML4_ADDR(265))
-#define DIRECTMAP_SIZE          (PML4_ENTRY_BYTES * (511 - 265))
+#define DIRECTMAP_VIRT_START    (PML4_ADDR(266))
+#define DIRECTMAP_SIZE          (PML4_ENTRY_BYTES * (511 - 266))
 #endif
 #define DIRECTMAP_VIRT_END      (DIRECTMAP_VIRT_START + DIRECTMAP_SIZE)
 
-- 
2.1.4


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