forked from Minki/linux
d3132b3860
Commita856531951("xen: make xen_qlock_wait() nestable") introduced a regression for Xen guests running fully virtualized (HVM or PVH mode). The Xen hypervisor wouldn't return from the poll hypercall with interrupts disabled in case of an interrupt (for PV guests it does). So instead of disabling interrupts in xen_qlock_wait() use a nesting counter to avoid calling xen_clear_irq_pending() in case xen_qlock_wait() is nested. Fixes:a856531951("xen: make xen_qlock_wait() nestable") Cc: stable@vger.kernel.org Reported-by: Sander Eikelenboom <linux@eikelenboom.it> Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Tested-by: Sander Eikelenboom <linux@eikelenboom.it> Signed-off-by: Juergen Gross <jgross@suse.com>
152 lines
3.6 KiB
C
152 lines
3.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Split spinlock implementation out into its own file, so it can be
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* compiled in a FTRACE-compatible way.
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*/
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#include <linux/kernel_stat.h>
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#include <linux/spinlock.h>
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#include <linux/debugfs.h>
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#include <linux/log2.h>
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#include <linux/gfp.h>
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#include <linux/slab.h>
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#include <linux/atomic.h>
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#include <asm/paravirt.h>
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#include <asm/qspinlock.h>
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#include <xen/interface/xen.h>
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#include <xen/events.h>
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#include "xen-ops.h"
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#include "debugfs.h"
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static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
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static DEFINE_PER_CPU(char *, irq_name);
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static DEFINE_PER_CPU(atomic_t, xen_qlock_wait_nest);
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static bool xen_pvspin = true;
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static void xen_qlock_kick(int cpu)
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{
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int irq = per_cpu(lock_kicker_irq, cpu);
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/* Don't kick if the target's kicker interrupt is not initialized. */
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if (irq == -1)
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return;
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xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
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}
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/*
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* Halt the current CPU & release it back to the host
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*/
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static void xen_qlock_wait(u8 *byte, u8 val)
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{
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int irq = __this_cpu_read(lock_kicker_irq);
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atomic_t *nest_cnt = this_cpu_ptr(&xen_qlock_wait_nest);
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/* If kicker interrupts not initialized yet, just spin */
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if (irq == -1 || in_nmi())
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return;
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/* Detect reentry. */
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atomic_inc(nest_cnt);
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/* If irq pending already and no nested call clear it. */
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if (atomic_read(nest_cnt) == 1 && xen_test_irq_pending(irq)) {
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xen_clear_irq_pending(irq);
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} else if (READ_ONCE(*byte) == val) {
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/* Block until irq becomes pending (or a spurious wakeup) */
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xen_poll_irq(irq);
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}
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atomic_dec(nest_cnt);
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}
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static irqreturn_t dummy_handler(int irq, void *dev_id)
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{
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BUG();
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return IRQ_HANDLED;
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}
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void xen_init_lock_cpu(int cpu)
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{
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int irq;
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char *name;
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if (!xen_pvspin) {
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if (cpu == 0)
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static_branch_disable(&virt_spin_lock_key);
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return;
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}
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WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
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cpu, per_cpu(lock_kicker_irq, cpu));
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name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
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irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
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cpu,
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dummy_handler,
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IRQF_PERCPU|IRQF_NOBALANCING,
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name,
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NULL);
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if (irq >= 0) {
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disable_irq(irq); /* make sure it's never delivered */
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per_cpu(lock_kicker_irq, cpu) = irq;
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per_cpu(irq_name, cpu) = name;
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}
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printk("cpu %d spinlock event irq %d\n", cpu, irq);
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}
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void xen_uninit_lock_cpu(int cpu)
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{
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if (!xen_pvspin)
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return;
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unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
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per_cpu(lock_kicker_irq, cpu) = -1;
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kfree(per_cpu(irq_name, cpu));
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per_cpu(irq_name, cpu) = NULL;
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}
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PV_CALLEE_SAVE_REGS_THUNK(xen_vcpu_stolen);
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/*
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* Our init of PV spinlocks is split in two init functions due to us
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* using paravirt patching and jump labels patching and having to do
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* all of this before SMP code is invoked.
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*
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* The paravirt patching needs to be done _before_ the alternative asm code
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* is started, otherwise we would not patch the core kernel code.
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*/
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void __init xen_init_spinlocks(void)
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{
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/* Don't need to use pvqspinlock code if there is only 1 vCPU. */
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if (num_possible_cpus() == 1)
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xen_pvspin = false;
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if (!xen_pvspin) {
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printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
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return;
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}
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printk(KERN_DEBUG "xen: PV spinlocks enabled\n");
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__pv_init_lock_hash();
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pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
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pv_ops.lock.queued_spin_unlock =
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PV_CALLEE_SAVE(__pv_queued_spin_unlock);
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pv_ops.lock.wait = xen_qlock_wait;
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pv_ops.lock.kick = xen_qlock_kick;
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pv_ops.lock.vcpu_is_preempted = PV_CALLEE_SAVE(xen_vcpu_stolen);
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}
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static __init int xen_parse_nopvspin(char *arg)
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{
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xen_pvspin = false;
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return 0;
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}
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early_param("xen_nopvspin", xen_parse_nopvspin);
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