[Xen-devel] [PATCH v2] x86/alt: Drop explicit padding of origin sites

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Now that the alternatives infrastructure can calculate the required padding
automatically, there is no need to hard code it.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/x86_64/compat/entry.S  |  2 +-
 xen/arch/x86/x86_64/entry.S         |  2 +-
 xen/include/asm-x86/nops.h          |  7 -------
 xen/include/asm-x86/spec_ctrl_asm.h | 19 ++++++++-----------
 4 files changed, 10 insertions(+), 20 deletions(-)

diff --git a/xen/arch/x86/x86_64/compat/entry.S 
b/xen/arch/x86/x86_64/compat/entry.S
index 8aba269..f650610 100644
--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -134,7 +134,7 @@ ENTRY(compat_restore_all_guest)
         jne   1b
 2:
 .endm
-       ALTERNATIVE_2 ".skip 45, 0x90", \
+       ALTERNATIVE_2 "", \
             alt_cr4_pv32, X86_FEATURE_XEN_SMEP, \
             alt_cr4_pv32, X86_FEATURE_XEN_SMAP
 
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index e939f20..cc94333 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -564,7 +564,7 @@ handle_exception_saved:
         testb $X86_EFLAGS_IF>>8,UREGS_eflags+1(%rsp)
         jz    exception_with_ints_disabled
 
-        ALTERNATIVE_2 "jmp .Lcr4_pv32_done; .skip 2, 0x90", \
+        ALTERNATIVE_2 "jmp .Lcr4_pv32_done", \
             __stringify(mov VCPU_domain(%rbx), %rax), X86_FEATURE_XEN_SMEP, \
             __stringify(mov VCPU_domain(%rbx), %rax), X86_FEATURE_XEN_SMAP
 
diff --git a/xen/include/asm-x86/nops.h b/xen/include/asm-x86/nops.h
index 61319cc..1a46b97 100644
--- a/xen/include/asm-x86/nops.h
+++ b/xen/include/asm-x86/nops.h
@@ -65,13 +65,6 @@
 #define ASM_NOP8 _ASM_MK_NOP(P6_NOP8)
 #define ASM_NOP9 _ASM_MK_NOP(P6_NOP9)
 
-#define ASM_NOP17 ASM_NOP8; ASM_NOP7; ASM_NOP2
-#define ASM_NOP21 ASM_NOP8; ASM_NOP8; ASM_NOP5
-#define ASM_NOP24 ASM_NOP8; ASM_NOP8; ASM_NOP8
-#define ASM_NOP29 ASM_NOP8; ASM_NOP8; ASM_NOP8; ASM_NOP5
-#define ASM_NOP32 ASM_NOP8; ASM_NOP8; ASM_NOP8; ASM_NOP8
-#define ASM_NOP40 ASM_NOP8; ASM_NOP8; ASM_NOP8; ASM_NOP8; ASM_NOP8
-
 #define ASM_NOP_MAX 9
 
 #endif /* __X86_ASM_NOPS_H__ */
diff --git a/xen/include/asm-x86/spec_ctrl_asm.h 
b/xen/include/asm-x86/spec_ctrl_asm.h
index 1f2b6f3..1623fc0 100644
--- a/xen/include/asm-x86/spec_ctrl_asm.h
+++ b/xen/include/asm-x86/spec_ctrl_asm.h
@@ -216,9 +216,8 @@
 
 /* Use after a VMEXIT from an HVM guest. */
 #define SPEC_CTRL_ENTRY_FROM_VMEXIT                                     \
-    ALTERNATIVE __stringify(ASM_NOP40),                                 \
-        DO_OVERWRITE_RSB, X86_FEATURE_RSB_VMEXIT;                       \
-    ALTERNATIVE_2 __stringify(ASM_NOP32),                               \
+    ALTERNATIVE "", DO_OVERWRITE_RSB, X86_FEATURE_RSB_VMEXIT;           \
+    ALTERNATIVE_2 "",                                                   \
         __stringify(DO_SPEC_CTRL_ENTRY_FROM_VMEXIT                      \
                     ibrs_val=SPEC_CTRL_IBRS),                           \
         X86_FEATURE_XEN_IBRS_SET,                                       \
@@ -228,9 +227,8 @@
 
 /* Use after an entry from PV context (syscall/sysenter/int80/int82/etc). */
 #define SPEC_CTRL_ENTRY_FROM_PV                                         \
-    ALTERNATIVE __stringify(ASM_NOP40),                                 \
-        DO_OVERWRITE_RSB, X86_FEATURE_RSB_NATIVE;                       \
-    ALTERNATIVE_2 __stringify(ASM_NOP21),                               \
+    ALTERNATIVE "", DO_OVERWRITE_RSB, X86_FEATURE_RSB_NATIVE;           \
+    ALTERNATIVE_2 "",                                                   \
         __stringify(DO_SPEC_CTRL_ENTRY maybexen=0                       \
                     ibrs_val=SPEC_CTRL_IBRS),                           \
         X86_FEATURE_XEN_IBRS_SET,                                       \
@@ -239,9 +237,8 @@
 
 /* Use in interrupt/exception context.  May interrupt Xen or PV context. */
 #define SPEC_CTRL_ENTRY_FROM_INTR                                       \
-    ALTERNATIVE __stringify(ASM_NOP40),                                 \
-        DO_OVERWRITE_RSB, X86_FEATURE_RSB_NATIVE;                       \
-    ALTERNATIVE_2 __stringify(ASM_NOP29),                               \
+    ALTERNATIVE "", DO_OVERWRITE_RSB, X86_FEATURE_RSB_NATIVE;           \
+    ALTERNATIVE_2 "",                                                   \
         __stringify(DO_SPEC_CTRL_ENTRY maybexen=1                       \
                     ibrs_val=SPEC_CTRL_IBRS),                           \
         X86_FEATURE_XEN_IBRS_SET,                                       \
@@ -250,13 +247,13 @@
 
 /* Use when exiting to Xen context. */
 #define SPEC_CTRL_EXIT_TO_XEN                                           \
-    ALTERNATIVE_2 __stringify(ASM_NOP17),                               \
+    ALTERNATIVE_2 "",                                                   \
         DO_SPEC_CTRL_EXIT_TO_XEN, X86_FEATURE_XEN_IBRS_SET,             \
         DO_SPEC_CTRL_EXIT_TO_XEN, X86_FEATURE_XEN_IBRS_CLEAR
 
 /* Use when exiting to guest context. */
 #define SPEC_CTRL_EXIT_TO_GUEST                                         \
-    ALTERNATIVE_2 __stringify(ASM_NOP24),                               \
+    ALTERNATIVE_2 "",                                                   \
         DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_XEN_IBRS_SET,           \
         DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_XEN_IBRS_CLEAR
 
-- 
2.1.4


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