[PATCH 3/8] x86/spec-ctrl: Turn the remaining SPEC_CTRL_{ENTRY,EXIT}_* into asm macros

Andrew Cooper posted 8 patches 5 months, 1 week ago
There is a newer version of this series
[PATCH 3/8] x86/spec-ctrl: Turn the remaining SPEC_CTRL_{ENTRY,EXIT}_* into asm macros
Posted by Andrew Cooper 5 months, 1 week ago
These have grown more complex over time, with some already having been
converted.

Provide full Requires/Clobbers comments, otherwise missing at this level of
indirection.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Wei Liu <wl@xen.org>
---
 xen/arch/x86/include/asm/spec_ctrl_asm.h | 37 ++++++++++++++++++------
 1 file changed, 28 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/include/asm/spec_ctrl_asm.h b/xen/arch/x86/include/asm/spec_ctrl_asm.h
index dd7c5e8bfc79..ee75f2bced42 100644
--- a/xen/arch/x86/include/asm/spec_ctrl_asm.h
+++ b/xen/arch/x86/include/asm/spec_ctrl_asm.h
@@ -219,26 +219,45 @@
 .endm
 
 /* Use after an entry from PV context (syscall/sysenter/int80/int82/etc). */
-#define SPEC_CTRL_ENTRY_FROM_PV                                         \
+.macro SPEC_CTRL_ENTRY_FROM_PV
+/*
+ * Requires %rsp=regs/cpuinfo, %rdx=0
+ * Clobbers %rax, %rcx, %rdx
+ */
     ALTERNATIVE "", __stringify(DO_SPEC_CTRL_COND_IBPB maybexen=0),     \
-        X86_FEATURE_IBPB_ENTRY_PV;                                      \
-    ALTERNATIVE "", DO_OVERWRITE_RSB, X86_FEATURE_SC_RSB_PV;            \
+        X86_FEATURE_IBPB_ENTRY_PV
+
+    ALTERNATIVE "", DO_OVERWRITE_RSB, X86_FEATURE_SC_RSB_PV
+
     ALTERNATIVE "", __stringify(DO_SPEC_CTRL_ENTRY maybexen=0),         \
         X86_FEATURE_SC_MSR_PV
+.endm
 
 /* Use in interrupt/exception context.  May interrupt Xen or PV context. */
-#define SPEC_CTRL_ENTRY_FROM_INTR                                       \
+.macro SPEC_CTRL_ENTRY_FROM_INTR
+/*
+ * Requires %rsp=regs, %r14=stack_end, %rdx=0
+ * Clobbers %rax, %rcx, %rdx
+ */
     ALTERNATIVE "", __stringify(DO_SPEC_CTRL_COND_IBPB maybexen=1),     \
-        X86_FEATURE_IBPB_ENTRY_PV;                                      \
-    ALTERNATIVE "", DO_OVERWRITE_RSB, X86_FEATURE_SC_RSB_PV;            \
+        X86_FEATURE_IBPB_ENTRY_PV
+
+    ALTERNATIVE "", DO_OVERWRITE_RSB, X86_FEATURE_SC_RSB_PV
+
     ALTERNATIVE "", __stringify(DO_SPEC_CTRL_ENTRY maybexen=1),         \
         X86_FEATURE_SC_MSR_PV
+.endm
 
 /* Use when exiting to PV guest context. */
-#define SPEC_CTRL_EXIT_TO_PV                                            \
-    ALTERNATIVE "",                                                     \
-        DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_SC_MSR_PV;              \
+.macro SPEC_CTRL_EXIT_TO_PV
+/*
+ * Requires %rax=spec_ctrl, %rsp=regs/info
+ * Clobbers %rcx, %rdx
+ */
+    ALTERNATIVE "", DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_SC_MSR_PV
+
     DO_SPEC_CTRL_COND_VERW
+.endm
 
 /*
  * Use in IST interrupt/exception context.  May interrupt Xen or PV context.
-- 
2.30.2


Re: [PATCH 3/8] x86/spec-ctrl: Turn the remaining SPEC_CTRL_{ENTRY,EXIT}_* into asm macros
Posted by Jan Beulich 5 months, 1 week ago
On 13.09.2023 22:27, Andrew Cooper wrote:
> These have grown more complex over time, with some already having been
> converted.
> 
> Provide full Requires/Clobbers comments, otherwise missing at this level of
> indirection.
> 
> No functional change.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>

>  /* Use when exiting to PV guest context. */
> -#define SPEC_CTRL_EXIT_TO_PV                                            \
> -    ALTERNATIVE "",                                                     \
> -        DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_SC_MSR_PV;              \
> +.macro SPEC_CTRL_EXIT_TO_PV
> +/*
> + * Requires %rax=spec_ctrl, %rsp=regs/info
> + * Clobbers %rcx, %rdx
> + */
> +    ALTERNATIVE "", DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_SC_MSR_PV
> +
>      DO_SPEC_CTRL_COND_VERW
> +.endm
>  
>  /*
>   * Use in IST interrupt/exception context.  May interrupt Xen or PV context.

I'll need to carefully rebase "x86/spec-ctrl: add logic to issue IBPB on
exit to guest" over this change. In particular the use of __LINE__ there
(which probably you didn't really like anyway) won't work anymore. Yet
with just a single use of the macro per source file we ought to be able
to get away without this extra label disambiguation ...

Jan