Patch-mainline: v5.6-rc3

Git-commit: 8645e56a4ad6dcbf504872db7f14a2f67db88ef2

References: bsc#1065600

From: Thomas Gleixner <tglx@linutronix.de>

Date: Wed, 19 Feb 2020 18:30:26 +0100

Subject: [PATCH] xen: Enable interrupts when calling _cond_resched()

xen_maybe_preempt_hcall() is called from the exception entry point

xen_do_hypervisor_callback with interrupts disabled.

_cond_resched() evades the might_sleep() check in cond_resched() which

would have caught that and schedule_debug() unfortunately lacks a check

for irqs_disabled().

Enable interrupts around the call and use cond_resched() to catch future

issues.

Fixes: fdfd811ddde3 ("x86/xen: allow privcmd hypercalls to be preempted")

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Link: https://lore.kernel.org/r/878skypjrh.fsf@nanos.tec.linutronix.de

Reviewed-by: Juergen Gross <jgross@suse.com>

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

---

 drivers/xen/preempt.c | 4 +++-

 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/preempt.c b/drivers/xen/preempt.c

index 8b9919c26095..456a164364a2 100644

--- a/drivers/xen/preempt.c

+++ b/drivers/xen/preempt.c

@@ -33,7 +33,9 @@ asmlinkage __visible void xen_maybe_preempt_hcall(void)

 		 * cpu.

 		 */

 		__this_cpu_write(xen_in_preemptible_hcall, false);

-		_cond_resched();

+		local_irq_enable();

+		cond_resched();

+		local_irq_disable();

 		__this_cpu_write(xen_in_preemptible_hcall, true);

 	}

 }

-- 

2.16.4