2019-06-27 05:09:02

by Xiaoyao Li

[permalink] [raw]
Subject: [PATCH] x86/boot: Make gdt 8-byte aligned

When loading segment descriptor, it uses lock implicitly. Align gdt here
to avoid potential split lock from crossing cache lines case.

Signed-off-by: Xiaoyao Li <[email protected]>
---
arch/x86/boot/compressed/head_64.S | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index fafb75c6c592..6233ae35d0d9 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -659,6 +659,7 @@ no_longmode:
gdt64:
.word gdt_end - gdt
.quad 0
+ .balign 8
gdt:
.word gdt_end - gdt
.long gdt
--
2.19.1


Subject: [tip:x86/boot] x86/boot: Make gdt 8-byte aligned

Commit-ID: 1c30fe6cbba6997ae4740bb46910036f8a4a9edb
Gitweb: https://git.kernel.org/tip/1c30fe6cbba6997ae4740bb46910036f8a4a9edb
Author: Xiaoyao Li <[email protected]>
AuthorDate: Thu, 27 Jun 2019 12:55:25 +0800
Committer: Thomas Gleixner <[email protected]>
CommitDate: Thu, 27 Jun 2019 09:40:41 +0200

x86/boot: Make gdt 8-byte aligned

The segment descriptors are loaded with a implicitly locked instruction,
which could trigger the split lock #AC if the variable is not properly
aligned and crosses a cache line.

Align gdt proper so the descriptors are 8 byte aligned.

Signed-off-by: Xiaoyao Li <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Fenghua Yu <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

---
arch/x86/boot/compressed/head_64.S | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index fafb75c6c592..6233ae35d0d9 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -659,6 +659,7 @@ no_longmode:
gdt64:
.word gdt_end - gdt
.quad 0
+ .balign 8
gdt:
.word gdt_end - gdt
.long gdt

Subject: [tip:x86/boot] x86/boot: Make the GDT 8-byte aligned

Commit-ID: 2238246ff8d533a5f2327d1f953375876d8a013c
Gitweb: https://git.kernel.org/tip/2238246ff8d533a5f2327d1f953375876d8a013c
Author: Xiaoyao Li <[email protected]>
AuthorDate: Thu, 27 Jun 2019 12:55:25 +0800
Committer: Ingo Molnar <[email protected]>
CommitDate: Thu, 27 Jun 2019 10:56:11 +0200

x86/boot: Make the GDT 8-byte aligned

The segment descriptors are loaded with an implicitly LOCK-ed instruction,
which could trigger the split lock #AC exception if the variable is not
properly aligned and crosses a cache line.

Align the GDT properly so the descriptors are all 8 byte aligned.

Signed-off-by: Xiaoyao Li <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Fenghua Yu <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/x86/boot/compressed/head_64.S | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index fafb75c6c592..6233ae35d0d9 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -659,6 +659,7 @@ no_longmode:
gdt64:
.word gdt_end - gdt
.quad 0
+ .balign 8
gdt:
.word gdt_end - gdt
.long gdt