[PATCH] config/arm: enable rcpc feature on neoverse n1

[PATCH] config/arm: enable rcpc feature on neoverse n1

[Joyce Kong]

Enable rcpc meson configuration for Neoverse N1 platform.

Signed-off-by: Joyce Kong <joyce.kong@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
---
 config/arm/meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/config/arm/meson.build b/config/arm/meson.build
index 5ff66248de..5213434ca4 100644
--- a/config/arm/meson.build
+++ b/config/arm/meson.build
@@ -65,7 +65,7 @@ part_number_config_arm = {
     '0xd0b': {'compiler_options':  ['-mcpu=cortex-a76']},
     '0xd0c': {
         'march': 'armv8.2-a',
-        'march_features': ['crypto'],
+        'march_features': ['crypto', 'rcpc'],
         'compiler_options':  ['-mcpu=neoverse-n1'],
         'flags': [
             ['RTE_MACHINE', '"neoverse-n1"'],
-- 
2.25.1

Re: [PATCH] config/arm: enable rcpc feature on neoverse n1

[Thomas Monjalon]

20/03/2023 04:26, Joyce Kong:
> Enable rcpc meson configuration for Neoverse N1 platform.

Please could you explain what it is in the commit message?

> -        'march_features': ['crypto'],
> +        'march_features': ['crypto', 'rcpc'],

RE: [PATCH] config/arm: enable rcpc feature on neoverse n1

[Joyce Kong]

> -----Original Message-----
> From: Thomas Monjalon <thomas@monjalon.net>
> Sent: Tuesday, March 21, 2023 12:10 AM
> To: dev@dpdk.org; Joyce Kong <Joyce.Kong@arm.com>
> Cc: Ruifeng Wang <Ruifeng.Wang@arm.com>; Bruce Richardson
> <bruce.richardson@intel.com>; nd <nd@arm.com>
> Subject: Re: [PATCH] config/arm: enable rcpc feature on neoverse n1
> 
> 20/03/2023 04:26, Joyce Kong:
> > Enable rcpc meson configuration for Neoverse N1 platform.
> 
> Please could you explain what it is in the commit message?
> 
Sure, I shall send out another version with the explanation.

> > -        'march_features': ['crypto'],
> > +        'march_features': ['crypto', 'rcpc'],
> 

[PATCH v2] config/arm: support ldapr on neoverse n1

[Joyce Kong]

Armv8.3 introduced a LDAPR instruction that has weaker guarantees,
just sufficient to implement memory_order_acq_rel. LDAPR does not
wait for previous STLR to complete. And if the same location is
used in both, it does not force the write to be globally observed.
The new instruction can avoid some costs associated with LDAR.

GCC13.0 has supported LDAPR.
For Armv8.3 and higher, LDAPR is default.
For Armv8.2 such as neoverse n1, LDAPR is supported with enabling
rcpc feature.
For Armv8.1 and lower, LDAPR is not supported.

Signed-off-by: Joyce Kong <joyce.kong@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
---
 config/arm/meson.build | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/config/arm/meson.build b/config/arm/meson.build
index 5ff66248de..5213434ca4 100644
--- a/config/arm/meson.build
+++ b/config/arm/meson.build
@@ -65,7 +65,7 @@ part_number_config_arm = {
     '0xd0b': {'compiler_options':  ['-mcpu=cortex-a76']},
     '0xd0c': {
         'march': 'armv8.2-a',
-        'march_features': ['crypto'],
+        'march_features': ['crypto', 'rcpc'],
         'compiler_options':  ['-mcpu=neoverse-n1'],
         'flags': [
             ['RTE_MACHINE', '"neoverse-n1"'],
-- 
2.25.1

Re: [PATCH v2] config/arm: support ldapr on neoverse n1

[Thomas Monjalon]

21/03/2023 10:44, Joyce Kong:
> Armv8.3 introduced a LDAPR instruction that has weaker guarantees,
> just sufficient to implement memory_order_acq_rel. LDAPR does not
> wait for previous STLR to complete. And if the same location is
> used in both, it does not force the write to be globally observed.
> The new instruction can avoid some costs associated with LDAR.
> 
> GCC13.0 has supported LDAPR.
> For Armv8.3 and higher, LDAPR is default.
> For Armv8.2 such as neoverse n1, LDAPR is supported with enabling
> rcpc feature.
> For Armv8.1 and lower, LDAPR is not supported.
> 
> Signed-off-by: Joyce Kong <joyce.kong@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>

Applied, thanks.