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

From: Julien Grall <julien@xen.org>
To: Rahul Singh <rahul.singh@arm.com>, xen-devel@lists.xenproject.org
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	Bertrand Marquis <bertrand.marquis@arm.com>,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>,
	Michal Orzel <michal.orzel@amd.com>
Subject: Re: [PATCH v4 3/7] xen/evtchn: restrict the maximum number of evtchn supported for domUs
Date: Wed, 7 Sep 2022 14:01:10 +0100	[thread overview]
Message-ID: <b04c4abf-9c7e-9b39-aafd-ece061a07197@xen.org> (raw)
In-Reply-To: <a631af9b5499eb3fab76cae372d623021431347c.1662462034.git.rahul.singh@arm.com>

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//

> 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@arm.com>
> Reviewed-by: Michal Orzel <michal.orzel@amd.com>
> ---
> 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@amazon.com>

Cheers,

-- 
Julien Grall