From: David Woodhouse <dwmw@xxxxxxxxxxxx> There's no need to swap pages (which involves three memcopies for each page) in the plain kexec case. Just do a single copy from source to destination page. Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> --- arch/x86/kernel/relocate_kernel_64.S | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S index fea650f92606..50cc33f2ecb7 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -310,6 +310,9 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages) movq %rdi, %rdx /* Save destination page to %rdx */ movq %rsi, %rax /* Save source page to %rax */ + testq %r11, %r11 /* Only actually swap for preserve_context */ + jz .Lnoswap + /* copy source page to swap page */ movq %r10, %rdi movl $512, %ecx @@ -324,6 +327,7 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages) /* copy swap page to destination page */ movq %rdx, %rdi movq %r10, %rsi +.Lnoswap: movl $512, %ecx rep ; movsq -- 2.47.0
