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Re: [PATCH v4 3/7] xen/evtchn: restrict the maximum number of evtchn supported for domUs


  • To: Julien Grall <julien@xxxxxxx>
  • From: Rahul Singh <Rahul.Singh@xxxxxxx>
  • Date: Wed, 7 Sep 2022 14:19:53 +0000
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  • Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>
  • Delivery-date: Wed, 07 Sep 2022 14:20:12 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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  • Thread-topic: [PATCH v4 3/7] xen/evtchn: restrict the maximum number of evtchn supported for domUs

Hi Julien,

> On 7 Sep 2022, at 2:01 pm, Julien Grall <julien@xxxxxxx> wrote:
> 
> 
> 
> On 06/09/2022 14:40, Rahul Singh wrote:
>> Restrict the maximum number of evtchn supported for domUs to avoid
>> allocating a large amount of memory in Xen.
>> Set the default value of max_evtchn_port to 1023. The value of 1023
>> should be sufficient for domUs guests because on ARM we don't bind
> 
> To me, domUs and guests mean the same. So s/guests//

Ack. 
> 
>> physical interrupts to event channels. The only use of the evtchn port
>> is inter-domain communications. Another reason why we choose the value
>> of 1023 to follow the default behavior of libxl.
>> Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
>> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
>> ---
>> Changes in v4:
>>  - fix minor comments in commit msg
>>  - Added Michal Reviewed-by
>> Changes in v3:
>>  - added in commit msg why we set the max_evtchn_port value to 1023.
>>  - added the comment in code also why we set the max_evtchn_port to 1023
>>  - remove the define and set the value to 1023 in code directly.
>> Changes in v2:
>>  - new patch in the version
>> ---
>>  xen/arch/arm/domain_build.c | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
>> index 3fd1186b53..fde133cd94 100644
>> --- a/xen/arch/arm/domain_build.c
>> +++ b/xen/arch/arm/domain_build.c
>> @@ -3277,7 +3277,13 @@ void __init create_domUs(void)
>>          struct xen_domctl_createdomain d_cfg = {
>>              .arch.gic_version = XEN_DOMCTL_CONFIG_GIC_NATIVE,
>>              .flags = XEN_DOMCTL_CDF_hvm | XEN_DOMCTL_CDF_hap,
>> -            .max_evtchn_port = -1,
>> +            /*
>> +             * The default of 1023 should be sufficient for domUs guests
> 
> To me, domUs and guests mean the same. So s/guests//
> 
> Same here. With that:
> 
> Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
> 
> Cheers,

Ack. 

Regards,
Rahul



 


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