linux-kernel - [PATCH v3 23/24] x86/resctrl: Expand resctrl_arch_update_domains()'s msr

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Date:   Wed, 19 May 2021 16:24:23 +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>
Subject: [PATCH v3 23/24] x86/resctrl: Expand resctrl_arch_update_domains()'s msr_param range

resctrl_arch_update_domains() specifies the one closid that has
been modified and needs copying to the hardware.
resctrl_arch_update_domains() takes a struct rdt_resource and a
closid as arguments, but copies all the staged configurations
for that closid into the ctrl_val[] array.

resctrl_arch_update_domains() is called once per schema, but
once the resources and domains are merged, the second call of
a L2CODE/L2DATA pair will find no staged configurations, as
they were previously applied. The msr_param of the first call
only has one index, so would only have update the hardware
for the last staged configuration.

To avoid a second round of IPIs when changing L2CODE and L2DATA
in one go, expand the range of the msr_param if multiple staged
configurations are found.

Signed-off-by: James Morse <james.morse@....com>
---
Changes since v2:
 * This patch is new.
---
 arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index e384398374da..0a1b878ca0db 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -292,6 +292,7 @@ int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid)
 		return -ENOMEM;
 
 	mba_sc = is_mba_sc(r);
+	msr_param.res = NULL;
 	list_for_each_entry(d, &r->domains, list) {
 		hw_dom = resctrl_to_arch_dom(d);
 		for (t = 0; t < CDP_NUM_TYPES; t++) {
@@ -303,9 +304,14 @@ int resctrl_arch_update_domains(struct rdt_resource *r, u32 closid)
 			if (!apply_config(hw_dom, cfg, idx, cpu_mask, mba_sc))
 				continue;
 
-			msr_param.low = idx;
-			msr_param.high = msr_param.low + 1;
-			msr_param.res = r;
+			if (!msr_param.res) {
+				msr_param.low = idx;
+				msr_param.high = msr_param.low + 1;
+				msr_param.res = r;
+			} else {
+				msr_param.low = min(msr_param.low, idx);
+				msr_param.high = max(msr_param.high, idx + 1);
+			}
 		}
 	}
 
-- 
2.30.2