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Message-ID: <172458943113.2215.12518487594417401349.tip-bot2@tip-bot2> Date: Sun, 25 Aug 2024 12:37:11 -0000 From: "tip-bot2 for Kai Huang" <tip-bot2@...utronix.de> To: linux-tip-commits@...r.kernel.org Cc: Kai Huang <kai.huang@...el.com>, Thomas Gleixner <tglx@...utronix.de>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, x86@...nel.org, linux-kernel@...r.kernel.org Subject: [tip: x86/cleanups] x86/kexec: Add comments around swap_pages() assembly to improve readability The following commit has been merged into the x86/cleanups branch of tip: Commit-ID: ea49cdb26e7cffc261ceb1db26707e6d337fa104 Gitweb: https://git.kernel.org/tip/ea49cdb26e7cffc261ceb1db26707e6d337fa104 Author: Kai Huang <kai.huang@...el.com> AuthorDate: Sun, 25 Aug 2024 20:18:06 +12:00 Committer: Thomas Gleixner <tglx@...utronix.de> CommitterDate: Sun, 25 Aug 2024 14:29:39 +02:00 x86/kexec: Add comments around swap_pages() assembly to improve readability The current assembly around swap_pages() in the relocate_kernel() takes some time to follow because the use of registers can be easily lost when the line of assembly goes long. Add a couple of comments to clarify the code around swap_pages() to improve readability. Signed-off-by: Kai Huang <kai.huang@...el.com> Signed-off-by: Thomas Gleixner <tglx@...utronix.de> Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> Link: https://lore.kernel.org/all/8b52b0b8513a34b2a02fb4abb05c6700c2821475.1724573384.git.kai.huang@intel.com --- arch/x86/kernel/relocate_kernel_64.S | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S index f7a3ca3..e9e88c3 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -170,6 +170,7 @@ 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 @@ -289,18 +290,21 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages) movq %rcx, %rsi /* For ever source page do a copy */ andq $0xfffffffffffff000, %rsi - movq %rdi, %rdx - movq %rsi, %rax + movq %rdi, %rdx /* Save destination page to %rdx */ + movq %rsi, %rax /* Save source page to %rax */ + /* copy source page to swap page */ movq %r10, %rdi movl $512, %ecx rep ; movsq + /* copy destination page to source page */ movq %rax, %rdi movq %rdx, %rsi movl $512, %ecx rep ; movsq + /* copy swap page to destination page */ movq %rdx, %rdi movq %r10, %rsi movl $512, %ecx
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