To determine whether the mba_MBps option to resctrl should be supported,
resctrl tests the boot CPUs' x86_vendor.
This isn't portable, and needs abstracting behind a helper so this check
can be part of the filesystem code that moves to /fs/.
Re-use the tests set_mba_sc() does to determine if the mba_sc is supported
on this system. An 'alloc_capable' test is added so that support for the
controls isn't implied by the 'delay_linear' property, which is always
true for MPAM.
Reviewed-by: Jamie Iles <[email protected]>
Tested-by: Xin Hao <[email protected]>
Reviewed-by: Shaopeng Tan <[email protected]>
Tested-by: Shaopeng Tan <[email protected]>
Tested-by: Cristian Marussi <[email protected]>
Signed-off-by: James Morse <[email protected]>
---
Changes since v3:
* Added use in resctrle_online_domain()
Changes since v1:
* Capitalisation
* Added MPAM example in commit message
* Fixed supports_mba_mbps() logic error in rdt_parse_param()
---
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index b32ceff8325a..49d9e2c3c743 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1890,17 +1890,26 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r)
}
/*
- * Enable or disable the MBA software controller
- * which helps user specify bandwidth in MBps.
* MBA software controller is supported only if
* MBM is supported and MBA is in linear scale.
*/
+static bool supports_mba_mbps(void)
+{
+ struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
+
+ return (is_mbm_enabled() &&
+ r->alloc_capable && is_mba_linear());
+}
+
+/*
+ * Enable or disable the MBA software controller
+ * which helps user specify bandwidth in MBps.
+ */
static int set_mba_sc(bool mba_sc)
{
struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
- if (!is_mbm_enabled() || !is_mba_linear() ||
- mba_sc == is_mba_sc(r))
+ if (!supports_mba_mbps() || mba_sc == is_mba_sc(r))
return -EINVAL;
r->membw.mba_sc = mba_sc;
@@ -2255,7 +2264,7 @@ static int rdt_parse_param(struct fs_context *fc, struct fs_parameter *param)
ctx->enable_cdpl2 = true;
return 0;
case Opt_mba_mbps:
- if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
+ if (!supports_mba_mbps())
return -EINVAL;
ctx->enable_mba_mbps = true;
return 0;
--
2.30.2
Hi James,
On 6/22/2022 9:46 AM, James Morse wrote:
...
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index b32ceff8325a..49d9e2c3c743 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1890,17 +1890,26 @@ void rdt_domain_reconfigure_cdp(struct rdt_resource *r)
> }
>
> /*
> - * Enable or disable the MBA software controller
> - * which helps user specify bandwidth in MBps.
> * MBA software controller is supported only if
> * MBM is supported and MBA is in linear scale.
> */
> +static bool supports_mba_mbps(void)
> +{
> + struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
> +
> + return (is_mbm_enabled() &&
> + r->alloc_capable && is_mba_linear());
> +}
> +
> +/*
> + * Enable or disable the MBA software controller
> + * which helps user specify bandwidth in MBps.
> + */
> static int set_mba_sc(bool mba_sc)
> {
> struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_MBA].r_resctrl;
>
> - if (!is_mbm_enabled() || !is_mba_linear() ||
> - mba_sc == is_mba_sc(r))
> + if (!supports_mba_mbps() || mba_sc == is_mba_sc(r))
> return -EINVAL;
>
> r->membw.mba_sc = mba_sc;
It seems that this change is propagating an issue that exists
in the current implementation (not introduced by this work).
The supports_mba_mbps() test uses is_mbm_enabled() which is:
(is_mbm_total_enabled() || is_mbm_local_enabled())
That is not accurate since the software controller is only called
when MBM local is enabled:
mbm_update()
{
...
if (is_mbm_local_enabled()) {
...
if (is_mba_sc(NULL))
mbm_bw_count(rmid, &rr);
}
}
Could the "is_mbm_enabled()" in the new supports_mba_mbps() introduced
here be changed to use "is_mbm_local_enabled()" instead? It does not seem
an issue for existing hardware (that supports total and local) but
the kernel parameters do enable users to boot with "rdt=!mbmlocal" to
trigger problematic scenarios.
Reinette