linux-kernel - [patch 12/12] x86/cacheinfo.c: check for block interference CPUs

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Date: Tue, 06 Feb 2024 15:49:23 -0300
From: Marcelo Tosatti <mtosatti@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Daniel Bristot de Oliveira <bristot@...nel.org>,
 Juri Lelli <juri.lelli@...hat.com>,
 Valentin Schneider <vschneid@...hat.com>,
 Frederic Weisbecker <frederic@...nel.org>,
 Leonardo Bras <leobras@...hat.com>,
 Peter Zijlstra <peterz@...radead.org>,
 Thomas Gleixner <tglx@...utronix.de>,
 Marcelo Tosatti <mtosatti@...hat.com>
Subject: [patch 12/12] x86/cacheinfo.c: check for block interference CPUs

Change amd_set_l3_disable_slot to check for block interference
cpumask, and avoid the IPI if set.

Also change wbinvd_on_cpu to use smp_call_function_single_fail.

Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>

Index: linux-isolation/arch/x86/include/asm/smp.h
===================================================================
--- linux-isolation.orig/arch/x86/include/asm/smp.h
+++ linux-isolation/arch/x86/include/asm/smp.h
@@ -118,7 +118,7 @@ int native_cpu_disable(void);
 void __noreturn hlt_play_dead(void);
 void native_play_dead(void);
 void play_dead_common(void);
-void wbinvd_on_cpu(int cpu);
+int wbinvd_on_cpu(int cpu);
 int wbinvd_on_all_cpus(void);
 
 void smp_kick_mwait_play_dead(void);
Index: linux-isolation/arch/x86/kernel/cpu/cacheinfo.c
===================================================================
--- linux-isolation.orig/arch/x86/kernel/cpu/cacheinfo.c
+++ linux-isolation/arch/x86/kernel/cpu/cacheinfo.c
@@ -17,6 +17,7 @@
 #include <linux/sysfs.h>
 #include <linux/pci.h>
 #include <linux/stop_machine.h>
+#include <linux/sched/isolation.h>
 
 #include <asm/cpufeature.h>
 #include <asm/cacheinfo.h>
@@ -396,6 +397,7 @@ static void amd_l3_disable_index(struct
 	 *  disable index in all 4 subcaches
 	 */
 	for (i = 0; i < 4; i++) {
+		int ret;
 		u32 reg = idx | (i << 20);
 
 		if (!nb->l3_cache.subcaches[i])
@@ -409,6 +411,7 @@ static void amd_l3_disable_index(struct
 		 * is not sufficient.
 		 */
 		ret = wbinvd_on_cpu(cpu);
+		WARN_ON(ret == -EPERM);
 
 		reg |= BIT(31);
 		pci_write_config_dword(nb->misc, 0x1BC + slot * 4, reg);
@@ -428,7 +431,7 @@ static void amd_l3_disable_index(struct
 static int amd_set_l3_disable_slot(struct amd_northbridge *nb, int cpu,
 			    unsigned slot, unsigned long index)
 {
-	int ret = 0;
+	int idx, ret = 0;
 
 	/*  check if @slot is already used or the index is already disabled */
 	ret = amd_get_l3_disable_slot(nb, slot);
@@ -442,7 +445,15 @@ static int amd_set_l3_disable_slot(struc
 	if (index == amd_get_l3_disable_slot(nb, !slot))
 		return -EEXIST;
 
-	amd_l3_disable_index(nb, cpu, slot, index);
+	ret = 0;
+	idx = block_interf_srcu_read_lock();
+
+	if (block_interf_cpu(cpu))
+		ret = -EPERM;
+	else
+		amd_l3_disable_index(nb, cpu, slot, index);
+
+	block_interf_srcu_read_unlock(idx);
 
 	return 0;
 }
Index: linux-isolation/arch/x86/lib/cache-smp.c
===================================================================
--- linux-isolation.orig/arch/x86/lib/cache-smp.c
+++ linux-isolation/arch/x86/lib/cache-smp.c
@@ -7,9 +7,9 @@ static void __wbinvd(void *dummy)
 	wbinvd();
 }
 
-void wbinvd_on_cpu(int cpu)
+int wbinvd_on_cpu(int cpu)
 {
-	smp_call_function_single(cpu, __wbinvd, NULL, 1);
+	return smp_call_function_single_fail(cpu, __wbinvd, NULL, 1);
 }
 EXPORT_SYMBOL(wbinvd_on_cpu);