EFI: add architecture functions for pre/post ExitBootServices

The UEFI ExitBootServices function is invoked to transition the
system to the 'runtime' mode of operation, and is done right before
transitioning from the EFI loader code into Xen proper. x86 does some
arch specific memory management (trampoline) before exit boot services,
and the code that transitions from the EFI application state to Xen
is architecture specific.  This patch adds two functions, one pre
and one post ExitBootServices to allow each architecture to
to handle these cases in a customized manner.

Signed-off-by: Roy Franz <roy.franz@linaro.org>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/efi/efi-boot.h

@@ -198,3 +198,53 @@ static void *__init efi_arch_allocate_mmap_buffer(UINTN map_size)
         return NULL;
     return (void *)(long)mbi.mem_upper;
 }
+
+static void __init efi_arch_pre_exit_boot(void)
+{
+    if ( !trampoline_phys )
+    {
+        if ( !cfg.addr )
+            blexit(L"No memory for trampoline");
+        relocate_trampoline(cfg.addr);
+    }
+}
+
+static void __init noreturn efi_arch_post_exit_boot(void)
+{
+    u64 efer;
+
+    efi_arch_relocate_image(__XEN_VIRT_START - xen_phys_start);
+    memcpy((void *)trampoline_phys, trampoline_start, cfg.size);
+
+    /* Set system registers and transfer control. */
+    asm volatile("pushq $0\n\tpopfq");
+    rdmsrl(MSR_EFER, efer);
+    efer |= EFER_SCE;
+    if ( cpuid_ext_features & (1 << (X86_FEATURE_NX & 0x1f)) )
+        efer |= EFER_NX;
+    wrmsrl(MSR_EFER, efer);
+    write_cr0(X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | X86_CR0_NE | X86_CR0_WP |
+              X86_CR0_AM | X86_CR0_PG);
+    asm volatile ( "mov    %[cr4], %%cr4\n\t"
+                   "mov    %[cr3], %%cr3\n\t"
+                   "movabs $__start_xen, %[rip]\n\t"
+                   "lgdt   gdt_descr(%%rip)\n\t"
+                   "mov    stack_start(%%rip), %%rsp\n\t"
+                   "mov    %[ds], %%ss\n\t"
+                   "mov    %[ds], %%ds\n\t"
+                   "mov    %[ds], %%es\n\t"
+                   "mov    %[ds], %%fs\n\t"
+                   "mov    %[ds], %%gs\n\t"
+                   "movl   %[cs], 8(%%rsp)\n\t"
+                   "mov    %[rip], (%%rsp)\n\t"
+                   "lretq  %[stkoff]-16"
+                   : [rip] "=&r" (efer/* any dead 64-bit variable */)
+                   : [cr3] "r" (idle_pg_table),
+                     [cr4] "r" (mmu_cr4_features),
+                     [cs] "ir" (__HYPERVISOR_CS),
+                     [ds] "r" (__HYPERVISOR_DS),
+                     [stkoff] "i" (STACK_SIZE - sizeof(struct cpu_info)),
+                     "D" (&mbi)
+                   : "memory" );
+    for( ; ; ); /* not reached */
+}

xen/common/efi/boot.c

@@ -668,7 +668,6 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
     EFI_GRAPHICS_OUTPUT_MODE_INFORMATION *mode_info;
     EFI_FILE_HANDLE dir_handle;
     union string section = { NULL }, name;
-    u64 efer;
     bool_t base_video = 0;
 
     efi_ih = ImageHandle;
@@ -1277,12 +1276,7 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
     efi_arch_process_memory_map(SystemTable, efi_memmap, efi_memmap_size,
                                 efi_mdesc_size, mdesc_ver);
 
-    if ( !trampoline_phys )
-    {
-        if ( !cfg.addr )
-            blexit(L"No memory for trampoline");
-        relocate_trampoline(cfg.addr);
-    }
+    efi_arch_pre_exit_boot();
 
     status = efi_bs->ExitBootServices(ImageHandle, map_key);
     if ( EFI_ERROR(status) )
@@ -1296,39 +1290,7 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
     efi_memmap = (void *)efi_memmap + DIRECTMAP_VIRT_START;
     efi_fw_vendor = (void *)efi_fw_vendor + DIRECTMAP_VIRT_START;
 
-    efi_arch_relocate_image(__XEN_VIRT_START - xen_phys_start);
-    memcpy((void *)trampoline_phys, trampoline_start, cfg.size);
-
-    /* Set system registers and transfer control. */
-    asm volatile("pushq $0\n\tpopfq");
-    rdmsrl(MSR_EFER, efer);
-    efer |= EFER_SCE;
-    if ( cpuid_ext_features & (1 << (X86_FEATURE_NX & 0x1f)) )
-        efer |= EFER_NX;
-    wrmsrl(MSR_EFER, efer);
-    write_cr0(X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | X86_CR0_NE | X86_CR0_WP |
-              X86_CR0_AM | X86_CR0_PG);
-    asm volatile ( "mov    %[cr4], %%cr4\n\t"
-                   "mov    %[cr3], %%cr3\n\t"
-                   "movabs $__start_xen, %[rip]\n\t"
-                   "lgdt   gdt_descr(%%rip)\n\t"
-                   "mov    stack_start(%%rip), %%rsp\n\t"
-                   "mov    %[ds], %%ss\n\t"
-                   "mov    %[ds], %%ds\n\t"
-                   "mov    %[ds], %%es\n\t"
-                   "mov    %[ds], %%fs\n\t"
-                   "mov    %[ds], %%gs\n\t"
-                   "movl   %[cs], 8(%%rsp)\n\t"
-                   "mov    %[rip], (%%rsp)\n\t"
-                   "lretq  %[stkoff]-16"
-                   : [rip] "=&r" (efer/* any dead 64-bit variable */)
-                   : [cr3] "r" (idle_pg_table),
-                     [cr4] "r" (mmu_cr4_features),
-                     [cs] "ir" (__HYPERVISOR_CS),
-                     [ds] "r" (__HYPERVISOR_DS),
-                     [stkoff] "i" (STACK_SIZE - sizeof(struct cpu_info)),
-                     "D" (&mbi)
-                   : "memory" );
+    efi_arch_post_exit_boot();
     for( ; ; ); /* not reached */
 }