This patch prepare decompression code to boot-time switching between 4-
and 5-level paging.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
arch/x86/boot/compressed/head_64.S | 16 ++++++++++++----
arch/x86/boot/compressed/pagetable.c | 19 +++++++++++++++++++
2 files changed, 31 insertions(+), 4 deletions(-)
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index b4a5d284391c..6ac8239af2b6 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -288,10 +288,18 @@ ENTRY(startup_64)
leaq boot_stack_end(%rbx), %rsp
#ifdef CONFIG_X86_5LEVEL
- /* Check if 5-level paging has already enabled */
- movq %cr4, %rax
- testl $X86_CR4_LA57, %eax
- jnz lvl5
+ /*
+ * Check if we need to enable 5-level paging.
+ * RSI holds real mode data and need to be preserved across
+ * a function call.
+ */
+ pushq %rsi
+ call need_to_enabled_l5
+ popq %rsi
+
+ /* If need_to_enabled_l5() returned zero, we're done here. */
+ cmpq $0, %rax
+ je lvl5
/*
* At this point we are in long mode with 4-level paging enabled,
diff --git a/arch/x86/boot/compressed/pagetable.c b/arch/x86/boot/compressed/pagetable.c
index a15bbfcb3413..cd2dd49333cc 100644
--- a/arch/x86/boot/compressed/pagetable.c
+++ b/arch/x86/boot/compressed/pagetable.c
@@ -154,3 +154,22 @@ void finalize_identity_maps(void)
}
#endif /* CONFIG_RANDOMIZE_BASE */
+
+#ifdef CONFIG_X86_5LEVEL
+int need_to_enabled_l5(void)
+{
+ /* Check i leaf 7 is supported. */
+ if (native_cpuid_eax(0) < 7)
+ return 0;
+
+ /* Check if la57 is supported. */
+ if (!(native_cpuid_ecx(7) & (1 << (X86_FEATURE_LA57 & 31))))
+ return 0;
+
+ /* Check if 5-level paging has already been enabled. */
+ if (native_read_cr4() & X86_CR4_LA57)
+ return 0;
+
+ return 1;
+}
+#endif
--
2.14.2
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