[PATCH 2/9] x86/kexec: Ensure preserve_context flag is set on return to kernel

[David Woodhouse]

From: David Woodhouse <d...@amazon.co.uk>

The swap_pages function will only actually *swap*, as its name implies,
if the preserve_context flag in the %r11 register is non-zero. On the
way back from a ::preserve_context kexec, ensure that the %r11 register
is non-zero so that the pages get swapped back.

Fixes: 9e5683e2d0b5 ("x86/kexec: Only swap pages for ::preserve_context mode")
Signed-off-by: David Woodhouse <d...@amazon.co.uk>
---
 arch/x86/kernel/relocate_kernel_64.S | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/relocate_kernel_64.S 
b/arch/x86/kernel/relocate_kernel_64.S
index 9bd601dd8659..1a52e4339c1d 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -220,6 +220,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
        movq    kexec_pa_table_page(%rip), %rax
        movq    %rax, %cr3
        lea     PAGE_SIZE(%r8), %rsp
+       movq    $1, %r11        /* Ensure preserve_context flag is set */
        call    swap_pages
        movq    kexec_va_control_page(%rip), %rax
        addq    $(virtual_mapped - relocate_kernel), %rax
-- 
2.47.0