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

[Jan Beulich]

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 

Reviewed-by: Jan Beulich 

>  /* 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

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

[Andrew Cooper]

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 
---
CC: Jan Beulich 
CC: Roger Pau Monné 
CC: Wei Liu 
---
 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