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Message-Id: <20181101095844.24462-8-mathieu.desnoyers@efficios.com>
Date: Thu, 1 Nov 2018 10:58:35 +0100
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Peter Zijlstra <peterz@...radead.org>,
"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
Boqun Feng <boqun.feng@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
Thomas Gleixner <tglx@...utronix.de>,
Andy Lutomirski <luto@...capital.net>,
Dave Watson <davejwatson@...com>, Paul Turner <pjt@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Russell King <linux@....linux.org.uk>,
Ingo Molnar <mingo@...hat.com>,
"H . Peter Anvin" <hpa@...or.com>,
Andi Kleen <andi@...stfloor.org>, Chris Lameter <cl@...ux.com>,
Ben Maurer <bmaurer@...com>,
Steven Rostedt <rostedt@...dmis.org>,
Josh Triplett <josh@...htriplett.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Michael Kerrisk <mtk.manpages@...il.com>,
Joel Fernandes <joelaf@...gle.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [RFC PATCH for 4.21 07/16] cpu_opv: limit amount of virtual address space used by cpu_opv
Introduce sysctl cpu_opv_va_max_bytes, which limits the amount of
virtual address space that can be used by cpu_opv.
Its default value is the maximum amount of virtual address space which
can be used by a single cpu_opv system call (e.g. 64 kB on x86).
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
CC: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Paul Turner <pjt@...gle.com>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Andy Lutomirski <luto@...capital.net>
CC: Andi Kleen <andi@...stfloor.org>
CC: Dave Watson <davejwatson@...com>
CC: Chris Lameter <cl@...ux.com>
CC: Ingo Molnar <mingo@...hat.com>
CC: "H. Peter Anvin" <hpa@...or.com>
CC: Ben Maurer <bmaurer@...com>
CC: Steven Rostedt <rostedt@...dmis.org>
CC: Josh Triplett <josh@...htriplett.org>
CC: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Andrew Morton <akpm@...ux-foundation.org>
CC: Russell King <linux@....linux.org.uk>
CC: Catalin Marinas <catalin.marinas@....com>
CC: Will Deacon <will.deacon@....com>
CC: Michael Kerrisk <mtk.manpages@...il.com>
CC: Boqun Feng <boqun.feng@...il.com>
CC: linux-api@...r.kernel.org
---
kernel/cpu_opv.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
kernel/sysctl.c | 15 ++++++++++++
2 files changed, 88 insertions(+), 1 deletion(-)
diff --git a/kernel/cpu_opv.c b/kernel/cpu_opv.c
index 6ee7ca3376be..309d20a35227 100644
--- a/kernel/cpu_opv.c
+++ b/kernel/cpu_opv.c
@@ -59,6 +59,16 @@
/* Maximum number of virtual addresses per op. */
#define CPU_OP_VEC_MAX_ADDR (2 * CPU_OP_VEC_LEN_MAX)
+/* Maximum address range size (aligned on SHMLBA) per virtual address. */
+#define CPU_OP_RANGE_PER_ADDR_MAX (2 * SHMLBA)
+
+/*
+ * Minimum value for sysctl_cpu_opv_va_max_bytes is the maximum virtual memory
+ * space needed by one cpu_opv system call.
+ */
+#define CPU_OPV_VA_MAX_BYTES_MIN \
+ (CPU_OP_VEC_MAX_ADDR * CPU_OP_RANGE_PER_ADDR_MAX)
+
union op_fn_data {
uint8_t _u8;
uint16_t _u16;
@@ -96,6 +106,15 @@ struct opv_ipi_args {
*/
static DEFINE_MUTEX(cpu_opv_offline_lock);
+/* Maximum virtual address space which can be used by cpu_opv. */
+int sysctl_cpu_opv_va_max_bytes __read_mostly;
+int sysctl_cpu_opv_va_max_bytes_min;
+
+static atomic_t cpu_opv_va_allocated_bytes;
+
+/* Waitqueue for cpu_opv blocked on virtual address space reservation. */
+static DECLARE_WAIT_QUEUE_HEAD(cpu_opv_va_wait);
+
/*
* The cpu_opv system call executes a vector of operations on behalf of
* user-space on a specific CPU either with interrupts disabled or within
@@ -489,6 +508,43 @@ static int cpu_opv_pin_pages_op(struct cpu_op *op,
return 0;
}
+/*
+ * Approximate the amount of virtual address space required per
+ * vaddr to a worse-case of CPU_OP_RANGE_PER_ADDR_MAX.
+ */
+static int cpu_opv_reserve_va(int nr_vaddr, int *reserved_va)
+{
+ int nr_bytes = nr_vaddr * CPU_OP_RANGE_PER_ADDR_MAX;
+ int old_bytes, new_bytes;
+
+ WARN_ON_ONCE(*reserved_va != 0);
+ if (nr_bytes > sysctl_cpu_opv_va_max_bytes) {
+ WARN_ON_ONCE(1);
+ return -EINVAL;
+ }
+ do {
+ wait_event(cpu_opv_va_wait,
+ (old_bytes = atomic_read(&cpu_opv_va_allocated_bytes)) +
+ nr_bytes <= sysctl_cpu_opv_va_max_bytes);
+ new_bytes = old_bytes + nr_bytes;
+ } while (atomic_cmpxchg(&cpu_opv_va_allocated_bytes,
+ old_bytes, new_bytes) != old_bytes);
+
+ *reserved_va = nr_bytes;
+ return 0;
+}
+
+static void cpu_opv_unreserve_va(int *reserved_va)
+{
+ int nr_bytes = *reserved_va;
+
+ if (!nr_bytes)
+ return;
+ atomic_sub(nr_bytes, &cpu_opv_va_allocated_bytes);
+ wake_up(&cpu_opv_va_wait);
+ *reserved_va = 0;
+}
+
static int cpu_opv_pin_pages(struct cpu_op *cpuop, int cpuopcnt,
struct cpu_opv_vaddr *vaddr_ptrs)
{
@@ -898,7 +954,7 @@ SYSCALL_DEFINE4(cpu_opv, struct cpu_op __user *, ucpuopv, int, cpuopcnt,
struct cpu_opv_vaddr vaddr_ptrs = {
.nr_vaddr = 0,
};
- int ret, i, nr_vaddr = 0;
+ int ret, i, nr_vaddr = 0, reserved_va = 0;
bool retry = false;
if (unlikely(flags & ~(CPU_OP_NR_FLAG | CPU_OP_VEC_LEN_MAX_FLAG)))
@@ -922,6 +978,9 @@ SYSCALL_DEFINE4(cpu_opv, struct cpu_op __user *, ucpuopv, int, cpuopcnt,
if (nr_vaddr > NR_VADDR)
return -EINVAL;
again:
+ ret = cpu_opv_reserve_va(nr_vaddr, &reserved_va);
+ if (ret)
+ goto end;
ret = cpu_opv_pin_pages(cpuopv, cpuopcnt, &vaddr_ptrs);
if (ret)
goto end;
@@ -946,6 +1005,7 @@ SYSCALL_DEFINE4(cpu_opv, struct cpu_op __user *, ucpuopv, int, cpuopcnt,
*/
if (vaddr_ptrs.nr_vaddr)
vm_unmap_aliases();
+ cpu_opv_unreserve_va(&reserved_va);
if (retry) {
retry = false;
vaddr_ptrs.nr_vaddr = 0;
@@ -953,3 +1013,15 @@ SYSCALL_DEFINE4(cpu_opv, struct cpu_op __user *, ucpuopv, int, cpuopcnt,
}
return ret;
}
+
+/*
+ * Dynamic initialization is required on sparc because SHMLBA is not a
+ * constant.
+ */
+static int __init cpu_opv_init(void)
+{
+ sysctl_cpu_opv_va_max_bytes = CPU_OPV_VA_MAX_BYTES_MIN;
+ sysctl_cpu_opv_va_max_bytes_min = CPU_OPV_VA_MAX_BYTES_MIN;
+ return 0;
+}
+core_initcall(cpu_opv_init);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index cc02050fd0c4..eb34c6be2aa4 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -175,6 +175,11 @@ extern int unaligned_dump_stack;
extern int no_unaligned_warning;
#endif
+#ifdef CONFIG_CPU_OPV
+extern int sysctl_cpu_opv_va_max_bytes;
+extern int sysctl_cpu_opv_va_max_bytes_min;
+#endif
+
#ifdef CONFIG_PROC_SYSCTL
/**
@@ -1233,6 +1238,16 @@ static struct ctl_table kern_table[] = {
.extra2 = &one,
},
#endif
+#ifdef CONFIG_CPU_OPV
+ {
+ .procname = "cpu_opv_va_max_bytes",
+ .data = &sysctl_cpu_opv_va_max_bytes,
+ .maxlen = sizeof(sysctl_cpu_opv_va_max_bytes),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &sysctl_cpu_opv_va_max_bytes_min,
+ },
+#endif
{ }
};
--
2.11.0
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