[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] xen/arm: p2m: Restrict preemption check in apply_p2m_changes
Hi Ian, On 06/05/15 09:31, Ian Campbell wrote: > On Tue, 2015-05-05 at 17:31 +0100, Julien Grall wrote: >> Hi Konrad, >> >> On 05/05/15 16:50, Konrad Rzeszutek Wilk wrote: >>>> --- >>>> xen/arch/arm/p2m.c | 4 +++- >>>> 1 file changed, 3 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c >>>> index 65efa94..59dd23a 100644 >>>> --- a/xen/arch/arm/p2m.c >>>> +++ b/xen/arch/arm/p2m.c >>>> @@ -948,6 +948,7 @@ static int apply_p2m_changes(struct domain *d, >>>> const unsigned long sgfn = paddr_to_pfn(start_gpaddr), >>>> egfn = paddr_to_pfn(end_gpaddr); >>>> const unsigned int preempt_count_limit = (op == MEMACCESS) ? 1 : >>>> 0x2000; >>>> + const bool_t preempt = !is_idle_vcpu(current); >>>> bool_t flush = false; >>>> bool_t flush_pt; >>>> >>>> @@ -980,7 +981,8 @@ static int apply_p2m_changes(struct domain *d, >>>> * always make at least one pass as long as preempt_count_limit is >>>> * initialized with a value >= 1. >>>> */ >>>> - if ( count >= preempt_count_limit && hypercall_preempt_check() ) >>>> + if ( preempt && count >= preempt_count_limit >>>> + && hypercall_preempt_check() ) >>> >>> Could you use the softirq_pending() check to deal when there are no >>> domains? >> >> apply_p2m_changes will only be called with no current domain (i.e idle >> vcpu) during DOM0 construction. > > I wonder if we could/should try and switch to d0:v0 sooner during the > build process? Is that even feasible? We would hide out the problem and rely on hypercall_preempt_check to always return 0 in non-hypercall context (i.e during DOM0 construction). The problem may come back if we decide to change the behavior of local_events_need_delivery or the interrupt subsystem. I think this should be properly fix by calling hypercall_preempt_check only when it's necessary. Regards, -- Julien Grall _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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