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xen/events: remove event handling recursion detection

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__xen_evtchn_do_upcall() contains guards against being called
recursively. This mechanism was introduced in the early pvops times
(kernel 2.6.26) when there were all the Xen backend drivers missing
from the upstream kernel, and some of those out-of-tree drivers were
enabling interrupts in their event handlers (which was explicitly
allowed in the initial XenoLinux).

Nowadays we don't need to support those old drivers any more and the
capability to allow recursive calls of __xen_evtchn_do_upcall() can
be removed.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Juergen Gross 2019-11-29 13:39:41 +01:00
parent b94ae8ad9f
commit 348be43384
1 changed files with 3 additions and 13 deletions
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16
drivers/xen/events/events_base.c
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@ -1213,31 +1213,21 @@ void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
notify_remote_via_irq(irq);
}
static DEFINE_PER_CPU(unsigned, xed_nesting_count);
static void __xen_evtchn_do_upcall(void)
{
struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
int cpu = get_cpu();
unsigned count;
int cpu = smp_processor_id();
do {
vcpu_info->evtchn_upcall_pending = 0;
if (__this_cpu_inc_return(xed_nesting_count) - 1)
goto out;
xen_evtchn_handle_events(cpu);
BUG_ON(!irqs_disabled());
count = __this_cpu_read(xed_nesting_count);
__this_cpu_write(xed_nesting_count, 0);
} while (count != 1 || vcpu_info->evtchn_upcall_pending);
virt_rmb(); /* Hypervisor can set upcall pending. */
out:
put_cpu();
} while (vcpu_info->evtchn_upcall_pending);
}
void xen_evtchn_do_upcall(struct pt_regs *regs)