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Date: Tue, 06 Feb 2024 15:49:12 -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 01/12] cpu isolation: basic block interference infrastructure
There are a number of codepaths in the kernel that interrupt
code execution in remote CPUs. A subset of such codepaths are
triggered from userspace and can therefore return errors.
Introduce a cpumask named "block interference", writable from userspace.
This cpumask (and associated helpers) can be used by code that executes
code on remote CPUs to optionally return an error.
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Index: linux-isolation/include/linux/sched/isolation.h
===================================================================
--- linux-isolation.orig/include/linux/sched/isolation.h
+++ linux-isolation/include/linux/sched/isolation.h
@@ -72,4 +72,28 @@ static inline bool cpu_is_isolated(int c
cpuset_cpu_is_isolated(cpu);
}
+#ifdef CONFIG_CPU_ISOLATION
+extern cpumask_var_t block_interf_cpumask;
+extern bool block_interf_cpumask_active;
+
+int block_interf_srcu_read_lock(void);
+void block_interf_srcu_read_unlock(int idx);
+
+void block_interf_assert_held(void);
+
+#else
+int block_interf_srcu_read_lock(void) { return 0; }
+void block_interf_srcu_read_unlock(int idx) { }
+void block_interf_assert_held(void) { }
+#endif
+
+static inline bool block_interf_cpu(int cpu)
+{
+#ifdef CONFIG_CPU_ISOLATION
+ if (block_interf_cpumask_active)
+ return cpumask_test_cpu(cpu, block_interf_cpumask);
+#endif
+ return false;
+}
+
#endif /* _LINUX_SCHED_ISOLATION_H */
Index: linux-isolation/kernel/sched/isolation.c
===================================================================
--- linux-isolation.orig/kernel/sched/isolation.c
+++ linux-isolation/kernel/sched/isolation.c
@@ -239,3 +239,109 @@ static int __init housekeeping_isolcpus_
return housekeeping_setup(str, flags);
}
__setup("isolcpus=", housekeeping_isolcpus_setup);
+
+struct srcu_struct block_interf_srcu;
+EXPORT_SYMBOL_GPL(block_interf_srcu);
+
+cpumask_var_t block_interf_cpumask;
+EXPORT_SYMBOL_GPL(block_interf_cpumask);
+
+bool block_interf_cpumask_active;
+EXPORT_SYMBOL_GPL(block_interf_cpumask_active);
+
+int block_interf_srcu_read_lock(void)
+{
+ return srcu_read_lock(&block_interf_srcu);
+}
+EXPORT_SYMBOL(block_interf_srcu_read_lock);
+
+void block_interf_srcu_read_unlock(int idx)
+{
+ srcu_read_unlock(&block_interf_srcu, idx);
+}
+EXPORT_SYMBOL(block_interf_srcu_read_unlock);
+
+void block_interf_assert_held(void)
+{
+ WARN_ON_ONCE(!srcu_read_lock_held(&block_interf_srcu));
+}
+EXPORT_SYMBOL(block_interf_assert_held);
+
+static ssize_t
+block_interf_cpumask_read(struct file *filp, char __user *ubuf,
+ size_t count, loff_t *ppos)
+{
+ char *mask_str;
+ int len;
+
+ len = snprintf(NULL, 0, "%*pb\n",
+ cpumask_pr_args(block_interf_cpumask)) + 1;
+ mask_str = kmalloc(len, GFP_KERNEL);
+ if (!mask_str)
+ return -ENOMEM;
+
+ len = snprintf(mask_str, len, "%*pb\n",
+ cpumask_pr_args(block_interf_cpumask));
+ if (len >= count) {
+ count = -EINVAL;
+ goto out_err;
+ }
+ count = simple_read_from_buffer(ubuf, count, ppos, mask_str, len);
+
+out_err:
+ kfree(mask_str);
+
+ return count;
+}
+
+static ssize_t
+block_interf_cpumask_write(struct file *filp, const char __user *ubuf,
+ size_t count, loff_t *ppos)
+{
+ cpumask_var_t block_interf_cpumask_new;
+ int err;
+
+ if (!zalloc_cpumask_var(&block_interf_cpumask_new, GFP_KERNEL))
+ return -ENOMEM;
+
+ err = cpumask_parse_user(ubuf, count, block_interf_cpumask_new);
+ if (err)
+ goto err_free;
+
+ cpumask_copy(block_interf_cpumask, block_interf_cpumask_new);
+ synchronize_srcu(&block_interf_srcu);
+ free_cpumask_var(block_interf_cpumask_new);
+
+ return count;
+
+err_free:
+ free_cpumask_var(block_interf_cpumask_new);
+
+ return err;
+}
+
+static const struct file_operations block_interf_cpumask_fops = {
+ .read = block_interf_cpumask_read,
+ .write = block_interf_cpumask_write,
+};
+
+static int __init block_interf_cpumask_init(void)
+{
+ int ret;
+
+ ret = init_srcu_struct(&block_interf_srcu);
+ if (ret)
+ return ret;
+
+ if (!zalloc_cpumask_var(&block_interf_cpumask, GFP_KERNEL))
+ return -ENOMEM;
+
+ debugfs_create_file_unsafe("block_interf_cpumask", 0644, NULL, NULL,
+ &block_interf_cpumask_fops);
+
+ block_interf_cpumask_active = true;
+ return 0;
+}
+
+late_initcall(block_interf_cpumask_init);
+
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