linux-kernel - [PATCH] arm64: paravirt: Disable IRQs during stolen_time_cpu_down

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Message-ID: <20220420204417.155194-1-quic_eberman@quicinc.com>
Date:   Wed, 20 Apr 2022 13:44:17 -0700
From:   Elliot Berman <quic_eberman@...cinc.com>
To:     Juergen Gross <jgross@...e.com>,
        "Srivatsa S. Bhat (VMware)" <srivatsa@...il.mit.edu>,
        Alexey Makhalov <amakhalov@...are.com>,
        "Catalin Marinas" <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
CC:     Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
        <virtualization@...ts.linux-foundation.org>, <x86@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Murali Nalajala <quic_mnalajal@...cinc.com>,
        Elliot Berman <quic_eberman@...cinc.com>
Subject: [PATCH] arm64: paravirt: Disable IRQs during stolen_time_cpu_down_prepare

From: Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>

During hotplug, the stolen time data structure is unmapped and memset.
There is a possibility of the timer IRQ being triggered before memset
and stolen time is getting updated as part of this timer IRQ handler. This
causes the below crash in timer handler -

  [ 3457.473139][    C5] Unable to handle kernel paging request at virtual address ffffffc03df05148
  ...
  [ 3458.154398][    C5] Call trace:
  [ 3458.157648][    C5]  para_steal_clock+0x30/0x50
  [ 3458.162319][    C5]  irqtime_account_process_tick+0x30/0x194
  [ 3458.168148][    C5]  account_process_tick+0x3c/0x280
  [ 3458.173274][    C5]  update_process_times+0x5c/0xf4
  [ 3458.178311][    C5]  tick_sched_timer+0x180/0x384
  [ 3458.183164][    C5]  __run_hrtimer+0x160/0x57c
  [ 3458.187744][    C5]  hrtimer_interrupt+0x258/0x684
  [ 3458.192698][    C5]  arch_timer_handler_virt+0x5c/0xa0
  [ 3458.198002][    C5]  handle_percpu_devid_irq+0xdc/0x414
  [ 3458.203385][    C5]  handle_domain_irq+0xa8/0x168
  [ 3458.208241][    C5]  gic_handle_irq.34493+0x54/0x244
  [ 3458.213359][    C5]  call_on_irq_stack+0x40/0x70
  [ 3458.218125][    C5]  do_interrupt_handler+0x60/0x9c
  [ 3458.223156][    C5]  el1_interrupt+0x34/0x64
  [ 3458.227560][    C5]  el1h_64_irq_handler+0x1c/0x2c
  [ 3458.232503][    C5]  el1h_64_irq+0x7c/0x80
  [ 3458.236736][    C5]  free_vmap_area_noflush+0x108/0x39c
  [ 3458.242126][    C5]  remove_vm_area+0xbc/0x118
  [ 3458.246714][    C5]  vm_remove_mappings+0x48/0x2a4
  [ 3458.251656][    C5]  __vunmap+0x154/0x278
  [ 3458.255796][    C5]  stolen_time_cpu_down_prepare+0xc0/0xd8
  [ 3458.261542][    C5]  cpuhp_invoke_callback+0x248/0xc34
  [ 3458.266842][    C5]  cpuhp_thread_fun+0x1c4/0x248
  [ 3458.271696][    C5]  smpboot_thread_fn+0x1b0/0x400
  [ 3458.276638][    C5]  kthread+0x17c/0x1e0
  [ 3458.280691][    C5]  ret_from_fork+0x10/0x20

As a fix, disable the IRQs during hotplug until we unmap and memset the
stolen time structure.

Signed-off-by: Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>
Signed-off-by: Elliot Berman <quic_eberman@...cinc.com>
---
 arch/arm64/kernel/paravirt.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c
index 75fed4460407..fc05a08557e0 100644
--- a/arch/arm64/kernel/paravirt.c
+++ b/arch/arm64/kernel/paravirt.c
@@ -70,13 +70,16 @@ static u64 para_steal_clock(int cpu)
 static int stolen_time_cpu_down_prepare(unsigned int cpu)
 {
 	struct pv_time_stolen_time_region *reg;
+	unsigned long flags;
 
 	reg = this_cpu_ptr(&stolen_time_region);
 	if (!reg->kaddr)
 		return 0;
 
+	local_irq_save(flags);
 	memunmap(reg->kaddr);
 	memset(reg, 0, sizeof(*reg));
+	local_irq_restore(flags);
 
 	return 0;
 }
-- 
2.25.1