linux-kernel - [PATCH v2] x86/kexec: Add a comment to relocate

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Message-Id: <20230612123438.469673-1-kai.huang@intel.com>
Date:   Tue, 13 Jun 2023 00:34:38 +1200
From:   Kai Huang <kai.huang@...el.com>
To:     linux-kernel@...r.kernel.org
Cc:     kirill.shutemov@...ux.intel.com, dave.hansen@...ux.intel.com,
        bp@...en8.de, tglx@...utronix.de, mingo@...hat.com,
        peterz@...radead.org, hpa@...or.com, x86@...nel.org,
        jpoimboe@...nel.org, rostedt@...dmis.org, konrad.wilk@...cle.com,
        Kai Huang <kai.huang@...el.com>
Subject: [PATCH v2] x86/kexec: Add a comment to relocate_kernel() for better readability

The reason to save %rcx to %r11 before calling swap_pages isn't that
obvious w/o looking into the swap_pages itself.  Add a comment to
improve the readability.

Signed-off-by: Kai Huang <kai.huang@...el.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---

v1 -> v2:
 - Avoided line split in the comment.
 - Added Kirill's Acked-by.

v1: https://lore.kernel.org/lkml/538335b164bf8b84b8a55c5654ed15d849479388.camel@intel.com/T/

---
 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 56cab1bb25f5..fea1aed16142 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -169,6 +169,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
 	wbinvd
 1:
 
+	/* Save the preserve_context to %r11 as swap_pages clobbers %rcx */
 	movq	%rcx, %r11
 	call	swap_pages
 

base-commit: 409bf2895d71bb68bc5b8589036e5ed1ca30bada
-- 
2.40.1