[PATCH 32/70] x86/head/64: Switch to initial stack earlier

Joerg Roedel
2020-03-19T09:18:21Z

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 --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 1be178be1566..b8ba72f31be9 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -194,6 +194,12 @@ 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
@@ -214,9 +220,6 @@ 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
--
2.17.1