[Xen-devel] [PATCH] x86: drop unneeded __packed attributes

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

There where a couple of unneeded packed attributes in several x86-specific
structures, that are obviously aligned. The only non-trivial one is
vmcb_struct, which has been checked to have the same layout with and without
the packed attribute using pahole. In that case add a build-time size check to
be on the safe side.

No functional change is expected as a result of this commit.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
This supersedes patch #1 in my clang 4.0 series. Patch #2 is still needed.
---
 xen/arch/x86/hvm/svm/vmcb.c            |  3 +++
 xen/arch/x86/x86_emulate/x86_emulate.h |  4 ++--
 xen/include/asm-x86/hvm/svm/vmcb.h     | 12 ++++++------
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/hvm/svm/vmcb.c b/xen/arch/x86/hvm/svm/vmcb.c
index 696cf99..d82c507 100644
--- a/xen/arch/x86/hvm/svm/vmcb.c
+++ b/xen/arch/x86/hvm/svm/vmcb.c
@@ -71,6 +71,9 @@ static int construct_vmcb(struct vcpu *v)
     struct arch_svm_struct *arch_svm = &v->arch.hvm_svm;
     struct vmcb_struct *vmcb = arch_svm->vmcb;
 
+    /* Build-time check of the size of VMCB AMD structure. */
+    BUILD_BUG_ON(sizeof(*vmcb) != 4096);
+
     vmcb->_general1_intercepts = 
         GENERAL1_INTERCEPT_INTR        | GENERAL1_INTERCEPT_NMI         |
         GENERAL1_INTERCEPT_SMI         | GENERAL1_INTERCEPT_INIT        |
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h 
b/xen/arch/x86/x86_emulate/x86_emulate.h
index c35873e..6e98453 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.h
+++ b/xen/arch/x86/x86_emulate/x86_emulate.h
@@ -108,7 +108,7 @@ struct x86_event {
  * Attribute for segment selector. This is a copy of bit 40:47 & 52:55 of the
  * segment descriptor. It happens to match the format of an AMD SVM VMCB.
  */
-typedef union __attribute__((__packed__)) segment_attributes {
+typedef union segment_attributes {
     uint16_t bytes;
     struct
     {
@@ -128,7 +128,7 @@ typedef union __attribute__((__packed__)) 
segment_attributes {
  * Full state of a segment register (visible and hidden portions).
  * Again, this happens to match the format of an AMD SVM VMCB.
  */
-struct __attribute__((__packed__)) segment_register {
+struct segment_register {
     uint16_t   sel;
     segment_attributes_t attr;
     uint32_t   limit;
diff --git a/xen/include/asm-x86/hvm/svm/vmcb.h 
b/xen/include/asm-x86/hvm/svm/vmcb.h
index 251e851..76a7368 100644
--- a/xen/include/asm-x86/hvm/svm/vmcb.h
+++ b/xen/include/asm-x86/hvm/svm/vmcb.h
@@ -307,7 +307,7 @@ enum VMEXIT_EXITCODE
 /* Definition of segment state is borrowed by the generic HVM code. */
 typedef struct segment_register svm_segment_register_t;
 
-typedef union __packed
+typedef union
 {
     u64 bytes;
     struct 
@@ -321,7 +321,7 @@ typedef union __packed
     } fields;
 } eventinj_t;
 
-typedef union __packed
+typedef union
 {
     u64 bytes;
     struct 
@@ -339,7 +339,7 @@ typedef union __packed
     } fields;
 } vintr_t;
 
-typedef union __packed
+typedef union
 {
     u64 bytes;
     struct 
@@ -356,7 +356,7 @@ typedef union __packed
     } fields;
 } ioio_info_t;
 
-typedef union __packed
+typedef union
 {
     u64 bytes;
     struct
@@ -365,7 +365,7 @@ typedef union __packed
     } fields;
 } lbrctrl_t;
 
-typedef union __packed
+typedef union
 {
     uint32_t bytes;
     struct
@@ -400,7 +400,7 @@ typedef union __packed
 #define IOPM_SIZE   (12 * 1024)
 #define MSRPM_SIZE  (8  * 1024)
 
-struct __packed vmcb_struct {
+struct vmcb_struct {
     u32 _cr_intercepts;         /* offset 0x00 - cleanbit 0 */
     u32 _dr_intercepts;         /* offset 0x04 - cleanbit 0 */
     u32 _exception_intercepts;  /* offset 0x08 - cleanbit 0 */
-- 
2.10.1 (Apple Git-78)


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel