From: David Woodhouse <d...@amazon.co.uk>
Add more comments explaining what each register contains, and save the
preserve_context flag to a non-clobbered register sooner, to keep things
simpler.
Signed-off-by: David Woodhouse <d...@amazon.co.uk>
---
arch/x86/kernel/relocate_kernel_64.S | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/relocate_kernel_64.S
b/arch/x86/kernel/relocate_kernel_64.S
index e9e88c342f75..c065806884f8 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -100,6 +100,9 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
movq %r10, CP_PA_SWAP_PAGE(%r11)
movq %rdi, CP_PA_BACKUP_PAGES_MAP(%r11)
+ /* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */
+ movq %rcx, %r11
+
/* Switch to the identity mapped page tables */
movq %r9, %cr3
@@ -116,6 +119,13 @@ SYM_CODE_END(relocate_kernel)
SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
UNWIND_HINT_END_OF_STACK
+ /*
+ * %rdi indirection page
+ * %rdx start address
+ * %r11 preserve_context
+ * %r12 host_mem_enc_active
+ */
+
/* set return address to 0 if not preserving context */
pushq $0
/* store the start address on the stack */
@@ -170,8 +180,6 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
wbinvd
.Lsme_off:
- /* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */
- movq %rcx, %r11
call swap_pages
/*
@@ -183,13 +191,14 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
movq %cr3, %rax
movq %rax, %cr3
+ testq %r11, %r11 /* preserve_context */
+ jnz .Lrelocate
+
/*
* set all of the registers to known values
* leave %rsp alone
*/
- testq %r11, %r11
- jnz .Lrelocate
xorl %eax, %eax
xorl %ebx, %ebx
xorl %ecx, %ecx
--
2.44.0
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