linux-kernel - [PATCH 2/2] x86: mmu.h: move mm_context_t::ia32

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Message-Id: <20190828193836.16791-2-linux@rasmusvillemoes.dk>
Date:   Wed, 28 Aug 2019 21:38:36 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] x86: mmu.h: move mm_context_t::ia32_compat member a bit down

For CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS=n, there's both a
6-byte hole after ia32_compat as well as a 4-byte hole after
perf_rdpmc_allowed. So rearranging things a bit we cut 8 bytes of
sizeof(struct mm_struct).

For a CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS=y kernel, this patch
just moves the 6-byte hole to another place in mm_context_t.

Putting the ia32_compat member after the pkey members is deliberate to
keep the latter two (when present) in the same 4-byte unit.

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 arch/x86/include/asm/mmu.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index b1bb47a3577b..ba3d22fcd507 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -32,10 +32,6 @@ typedef struct {
 	struct ldt_struct	*ldt;
 	struct mutex		lock;
 #endif
-#ifdef CONFIG_X86_64
-	/* True if mm supports a task running in 32 bit compatibility mode. */
-	unsigned short ia32_compat;
-#endif
 
 	void __user *vdso;			/* vdso base address */
 	const struct vdso_image *vdso_image;	/* vdso image in use */
@@ -49,6 +45,10 @@ typedef struct {
 	u16 pkey_allocation_map;
 	s16 execute_only_pkey;
 #endif
+#ifdef CONFIG_X86_64
+	/* True if mm supports a task running in 32 bit compatibility mode. */
+	unsigned short ia32_compat;
+#endif
 #ifdef CONFIG_X86_INTEL_MPX
 	/* address of the bounds directory */
 	void __user *bd_addr;
-- 
2.20.1