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

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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@amazon.co.uk>
Signed-off-by: Ingo 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
This commit is contained in:
David Woodhouse 2024-12-05 15:05:10 +00:00 • committed by Ingo Molnar
parent 46d4e205e2
commit 9e5683e2d0
1 changed files with 4 additions and 0 deletions
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4
arch/x86/kernel/relocate_kernel_64.S
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@ -310,6 +310,9 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
movq %rdi, %rdx /* Save destination page to %rdx */ movq %rdi, %rdx /* Save destination page to %rdx */
movq %rsi, %rax /* Save source page to %rax */ 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 */ /* copy source page to swap page */
movq %r10, %rdi movq %r10, %rdi
movl $512, %ecx movl $512, %ecx
@ -324,6 +327,7 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
/* copy swap page to destination page */ /* copy swap page to destination page */
movq %rdx, %rdi movq %rdx, %rdi
movq %r10, %rsi movq %r10, %rsi
.Lnoswap:
movl $512, %ecx movl $512, %ecx
rep ; movsq rep ; movsq