diff mbox series

[28/62] x86/head/64: Switch to initial stack earlier

Message ID 20200211135256.24617-29-joro@8bytes.org (mailing list archive)
State New, archived
Headers show
Series Linux as SEV-ES Guest Support | expand

Commit Message

Joerg Roedel Feb. 11, 2020, 1:52 p.m. UTC 
From: Joerg Roedel <jroedel@suse.de>

Make sure there is a stack once the kernel runs from virual addresses.
At this stage any secondary CPU which boots will have lost its stack
because the kernel switched to a new page-table which does not map the
real-mode stack anymore.

This is also needed for handling early #VC exceptions caused by
instructions like CPUID.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/kernel/head_64.S | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 36f2f30ad200..eefd6838b895 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -188,6 +188,12 @@  SYM_CODE_START(secondary_startup_64)
 	movl	initial_gs+4(%rip),%edx
 	wrmsr
 
+	/*
+	 * Setup a boot time stack - Any secondary CPU will have lost its stack
+	 * by now because the cr3-switch above unmaps the real-mode stack
+	 */
+	movq initial_stack(%rip), %rsp
+
 	/* Check if nx is implemented */
 	movl	$0x80000001, %eax
 	cpuid
@@ -208,9 +214,6 @@  SYM_CODE_START(secondary_startup_64)
 	/* Make changes effective */
 	movq	%rax, %cr0
 
-	/* Setup a boot time stack */
-	movq initial_stack(%rip), %rsp
-
 	/* zero EFLAGS after setting rsp */
 	pushq $0
 	popfq