linux-kernel - [PATCH v3 10/21] x86/resctrl: Abstract and use supports_mba

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Message-Id: <20220217182110.7176-11-james.morse@arm.com>
Date:   Thu, 17 Feb 2022 18:20:59 +0000
From:   James Morse <james.morse@....com>
To:     x86@...nel.org, linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        James Morse <james.morse@....com>,
        shameerali.kolothum.thodi@...wei.com,
        Jamie Iles <jamie@...iainc.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        lcherian@...vell.com, bobo.shaobowang@...wei.com,
        tan.shaopeng@...itsu.com
Subject: [PATCH v3 10/21] x86/resctrl: Abstract and use supports_mba_mbps()

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: Shaopeng Tan <tan.shaopeng@...itsu.com>
Signed-off-by: James Morse <james.morse@....com>
---
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 22ebfdb4472d..7ec089d72ab7 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1922,11 +1922,21 @@ static void mba_sc_domain_destroy(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;
@@ -1934,8 +1944,7 @@ static int set_mba_sc(bool mba_sc)
 	struct rdt_domain *d;
 	int i;
 
-	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;
@@ -2295,7 +2304,7 @@ 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