linux-kernel - [PATCH 2/2] x86/paravirt: Make the struct paravirt_patch

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Message-Id: <6dcb20159ded36586c5f7f2ae159e4e030256627.1686301237.git.houwenlong.hwl@antgroup.com>
Date:   Fri, 09 Jun 2023 17:45:32 +0800
From:   "Hou Wenlong" <houwenlong.hwl@...group.com>
To:     linux-kernel@...r.kernel.org
Cc:     "Lai Jiangshan" <jiangshan.ljs@...group.com>,
        "Hou Wenlong" <houwenlong.hwl@...group.com>,
        "Nadav Amit" <namit@...are.com>, "Juergen Gross" <jgross@...e.com>,
        "Ajay Kaher" <akaher@...are.com>,
        "Alexey Makhalov" <amakhalov@...are.com>,
        "VMware PV-Drivers Reviewers" <pv-drivers@...are.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...hat.com>, "Borislav Petkov" <bp@...en8.de>,
        "Dave Hansen" <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        <virtualization@...ts.linux-foundation.org>
Subject: [PATCH 2/2] x86/paravirt: Make the struct paravirt_patch_site packed

Similar to struct alt_instr, make the struct paravirt_patch_site packed
and get rid of all the .align directives. This could save 2 bytes for
one entry on X86_64.

Suggested-by: Nadav Amit <namit@...are.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
 arch/x86/include/asm/paravirt.h       | 2 --
 arch/x86/include/asm/paravirt_types.h | 4 +---
 2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 2350ceb43db0..3e5ccacb3893 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -747,11 +747,9 @@ extern void default_banner(void);
 	ops;					\
 772:;						\
 	.pushsection .parainstructions,"a";	\
-	 .align	4;				\
 	 .long 771b-.;				\
 	 .byte ptype;				\
 	 .byte 772b-771b;			\
-	 .align 4;				\
 	.popsection
 
 
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 982a234f5a06..da0547bcd068 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -8,7 +8,7 @@ struct paravirt_patch_site {
 	s32 instr_offset;	/* original instructions */
 	u8 type;		/* type of this instruction */
 	u8 len;			/* length of original instruction */
-};
+} __packed;
 
 /* Lazy mode for batching updates / context switch */
 enum paravirt_lazy_mode {
@@ -270,11 +270,9 @@ extern struct paravirt_patch_template pv_ops;
 #define _paravirt_alt(insn_string, type)		\
 	"771:\n\t" insn_string "\n" "772:\n"		\
 	".pushsection .parainstructions,\"a\"\n"	\
-	"  .align 4\n"					\
 	"  .long 771b-.\n"				\
 	"  .byte " type "\n"				\
 	"  .byte 772b-771b\n"				\
-	"  .align 4\n"					\
 	".popsection\n"
 
 /* Generate patchable code, with the default asm parameters. */
-- 
2.31.1