Commit 9e5683e2 authored by David Woodhouse's avatar David Woodhouse Committed by Ingo Molnar
Browse files

x86/kexec: Only swap pages for ::preserve_context mode 



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: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20241205153343.3275139-5-dwmw2@infradead.org
parent 46d4e205

arch/x86/kernel/relocate_kernel_64.S

+4 −0
Original line number Diff line number Diff line
@@ -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