diff mbox series

[v6,05/12] x86/alternative: support ALTERNATIVE_TERNARY

Message ID 20210309134813.23912-6-jgross@suse.com (mailing list archive)
State Superseded
Headers show
Series x86: major paravirt cleanup | expand

Commit Message

Jürgen Groß March 9, 2021, 1:48 p.m. UTC
Add ALTERNATIVE_TERNARY support for replacing an initial instruction
with either of two instructions depending on a feature:

  ALTERNATIVE_TERNARY "default_instr", FEATURE_NR,
                      "feature_on_instr", "feature_off_instr"

which will start with "default_instr" and at patch time will, depending
on FEATURE_NR being set or not, patch that with either
"feature_on_instr" or "feature_off_instr".

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
V3:
- new patch
V4:
- use X86_FEATURE_ALWAYS instead of negated feature (Boris Petkov)
- unfortunately this isn't enough to get rid of the "not feature"
  support, as this is needed in the patch "x86/paravirt: switch
  functions with custom code to ALTERNATIVE", too
V5:
- carve out the "not feature" part
---
 arch/x86/include/asm/alternative-asm.h | 4 ++++
 arch/x86/include/asm/alternative.h     | 6 ++++++
 2 files changed, 10 insertions(+)

Comments

Borislav Petkov March 10, 2021, 2:27 p.m. UTC | #1
On Tue, Mar 09, 2021 at 02:48:06PM +0100, Juergen Gross wrote:
> diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
> index 89889618ae01..4fb844e29d26 100644
> --- a/arch/x86/include/asm/alternative.h
> +++ b/arch/x86/include/asm/alternative.h
> @@ -178,6 +178,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
>  	ALTINSTR_REPLACEMENT(newinstr2, 2)				\
>  	".popsection\n"
>  
> +#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2)	\
> +	ALTERNATIVE_2(oldinstr, newinstr2, X86_FEATURE_ALWAYS, newinstr1, feature)

Make that:

/*
 * If @feature is set, patch @newinstr_yes, else @newinstr_no
 */
#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
        ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, newinstr_yes, feature)

and in alternative-asm.h too pls.

Regardless, this looks nice! :)

Thx.
Jürgen Groß March 10, 2021, 2:42 p.m. UTC | #2
On 10.03.21 15:27, Borislav Petkov wrote:
> On Tue, Mar 09, 2021 at 02:48:06PM +0100, Juergen Gross wrote:
>> diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
>> index 89889618ae01..4fb844e29d26 100644
>> --- a/arch/x86/include/asm/alternative.h
>> +++ b/arch/x86/include/asm/alternative.h
>> @@ -178,6 +178,9 @@ static inline int alternatives_text_reserved(void *start, void *end)
>>   	ALTINSTR_REPLACEMENT(newinstr2, 2)				\
>>   	".popsection\n"
>>   
>> +#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2)	\
>> +	ALTERNATIVE_2(oldinstr, newinstr2, X86_FEATURE_ALWAYS, newinstr1, feature)
> 
> Make that:
> 
> /*
>   * If @feature is set, patch @newinstr_yes, else @newinstr_no
>   */
> #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
>          ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, newinstr_yes, feature)
> 
> and in alternative-asm.h too pls.

Okay.

> 
> Regardless, this looks nice! :)

Thanks,


Juergen
diff mbox series

Patch

diff --git a/arch/x86/include/asm/alternative-asm.h b/arch/x86/include/asm/alternative-asm.h
index 3965daf0460e..80bc6b533358 100644
--- a/arch/x86/include/asm/alternative-asm.h
+++ b/arch/x86/include/asm/alternative-asm.h
@@ -112,6 +112,10 @@ 
 	.popsection
 .endm
 
+#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2)	\
+	ALTERNATIVE_2 oldinstr, newinstr2, X86_FEATURE_ALWAYS,		\
+	newinstr1, feature
+
 #endif  /*  __ASSEMBLY__  */
 
 #endif /* _ASM_X86_ALTERNATIVE_ASM_H */
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 89889618ae01..4fb844e29d26 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -178,6 +178,9 @@  static inline int alternatives_text_reserved(void *start, void *end)
 	ALTINSTR_REPLACEMENT(newinstr2, 2)				\
 	".popsection\n"
 
+#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2)	\
+	ALTERNATIVE_2(oldinstr, newinstr2, X86_FEATURE_ALWAYS, newinstr1, feature)
+
 #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, feat3) \
 	OLDINSTR_3(oldinsn, 1, 2, 3)						\
 	".pushsection .altinstructions,\"a\"\n"					\
@@ -209,6 +212,9 @@  static inline int alternatives_text_reserved(void *start, void *end)
 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
 	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
 
+#define alternative_ternary(oldinstr, feature, newinstr1, newinstr2)	\
+	asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2) ::: "memory")
+
 /*
  * Alternative inline assembly with input.
  *