[PATCH 1/2] x86/efi: Simplify efi_arch_cpu() a little

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Make the "no extended leaves" case fatal and remove one level of indentation.
Defer the max-leaf aquisition until it is first used.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
CC: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
CC: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
CC: Gene Bright <gene@xxxxxxxxxxxxx>
---
 xen/arch/x86/efi/efi-boot.h | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
index f282358435f1..4e4be7174751 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -738,29 +738,30 @@ static void __init efi_arch_handle_module(const struct 
file *file,
 
 static void __init efi_arch_cpu(void)
 {
-    uint32_t eax = cpuid_eax(0x80000000U);
+    uint32_t eax;
     uint32_t *caps = boot_cpu_data.x86_capability;
 
     boot_tsc_stamp = rdtsc();
 
     caps[FEATURESET_1c] = cpuid_ecx(1);
 
-    if ( (eax >> 16) == 0x8000 && eax > 0x80000000U )
-    {
-        caps[FEATURESET_e1d] = cpuid_edx(0x80000001U);
+    eax = cpuid_eax(0x80000000U);
+    if ( (eax >> 16) != 0x8000 || eax < 0x80000000U )
+        blexit(L"In 64bit mode, but no extended CPUID leaves?!?");
 
-        /*
-         * This check purposefully doesn't use cpu_has_nx because
-         * cpu_has_nx bypasses the boot_cpu_data read if Xen was compiled
-         * with CONFIG_REQUIRE_NX
-         */
-        if ( IS_ENABLED(CONFIG_REQUIRE_NX) &&
-             !boot_cpu_has(X86_FEATURE_NX) )
-            blexit(L"This build of Xen requires NX support");
+    caps[FEATURESET_e1d] = cpuid_edx(0x80000001U);
 
-        if ( cpu_has_nx )
-            trampoline_efer |= EFER_NXE;
-    }
+    /*
+     * This check purposefully doesn't use cpu_has_nx because
+     * cpu_has_nx bypasses the boot_cpu_data read if Xen was compiled
+     * with CONFIG_REQUIRE_NX
+     */
+    if ( IS_ENABLED(CONFIG_REQUIRE_NX) &&
+         !boot_cpu_has(X86_FEATURE_NX) )
+        blexit(L"This build of Xen requires NX support");
+
+    if ( cpu_has_nx )
+        trampoline_efer |= EFER_NXE;
 }
 
 static void __init efi_arch_blexit(void)
-- 
2.39.2